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Ignatius Rigor

Senior Principal Research Scientist

Affiliate Assistant Professor, Oceanography






Ignatius Rigor is the Coordinator of the International Arctic Buoy Program (IABP). His primary interests are in the use of data from the buoys to study air, sea, and ice interaction. His recent work has focused on analyzing surface air temperature observations in the Arctic, studying sea ice processes in the Russian marginal seas, and backtracking the source areas of pollutants found in sea ice. He joined the professional staff in 1987 after having worked in the APL-UW Student Assistant Program as an undergraduate.

Department Affiliation

Polar Science Center


B.S. Biology, University of Washington, 1986


International Arctic Buoy Programme

The participants of the IABP work together to maintain a network of drifting buoys in the Arctic Ocean to provide meteorological and oceanographic data for real-time operational requirements and research purposes including support to the World Climate Research Programme and the World Weather Watch Programme.


Sea Ice Thickness Estimates Obtained from Satellites Using Submarines and Other In Situ Observations

We compare the observations of arctic sea ice thickness estimates from satellites with in situ observations %u2013 collected by submarine cruises and moorings under the sea ice, by direct measurement during field camps, by electromagnetic instruments flown over the sea ice, and by buoys drifting with the sea ice %u2013 to provide a careful assessment of our capabilities to monitor the thickness of sea ice.


Arctic Surface Air Temperatures for the Past 100 Years

Accurate fields of Arctic surface air temperature (SAT) are needed for climate studies, but a robust gridded data set of SAT of sufficient length is not available over the entire Arctic. We plan to produce authoritative SAT data sets covering the Arctic Ocean from 1901 to present, which will be used to better understand Arctic climate change.


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UpTempO: Measuring the Upper Layer Temperature of the Arctic Ocean

This project aims to measure the time history of summer warming and subsequent fall cooling of the seasonally open water areas of the Arctic Ocean. Investigators will focus on those areas with the greatest ice retreat i.e., the northern Beaufort, Chukchi, East Siberian, and Laptev seas. Their method will be to build up to 10 relatively inexpensive ocean thermistor string buoys per year, to be deployed in the seasonally ice-free regions of the Arctic Ocean. Arctic-ADOS buoy data will be provided to both the research and operational weather forecasting communities in near real time on the International Arctic Buoy Program (IABP) web site.


Forecasting the Condition of Arctic Sea Ice on Daily to Seasonal Time Scales

The extent of arctic sea ice during the summer has declined to near-record minima during the last several summers. Can we predict future minima? Our weekly to seasonal forecasts provided by the National/Naval Ice Center help residents and navigators in the Arctic make better decisions regarding sea ice.

31 Dec 1969


Polar Science Weekend @ Pacific Science Center

This annual event at the Pacific Science Center shares polar science with thousands of visitors. APL-UW researchers inspire appreciation and interest in polar science through dozens of live demonstrations and hands-on activities.

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10 Mar 2017

Polar research and technology were presented to thousands of visitors by APL-UW staff during the Polar Science Weekend at Seattle's Pacific Science Center. The goal of is to inspire an appreciation and interest in science through one-on-one, face-to-face interactions between visitors and scientists. Guided by their 'polar passports', over 10,000 visitors learned about the Greenland ice sheet, the diving behavior of narwhals, the difference between sea ice and freshwater ice, how Seagliders work, and much more as they visited dozens of live demonstrations and activities.

The Polar Science Weekend has grown from an annual outreach event to an educational research project funded by NASA, and has become a model for similar activities hosted by the Pacific Science Center. A new program trains scientists and volunteers how to interact with the public and how to design engaging exhibits.

Snow Accumulations on Arctic Sea Ice

Snow plays a key role in the growth and decay of Arctic sea ice each year. APL-UW research assesses spring snow depth distribution on Arctic sea ice using airborne radar observations from Operation IceBridge compared with in situ measurements taken in spring 2012 and historical data from the Soviet drifting ice stations of the mid-20th century. Snow depths have declined in the western Arctic and Beaufort and Chukchi seas. Thinning is correlated with the delayed onset of sea ice freeze-up during autumn.

11 Sep 2014

Sensor-Rich Buoys in the Arctic Ocean

As arctic sea ice transitions from a multi-year to a more seasonal ice pack, buoys deployed by the International Arctic Buoy Programme have required improvements to better survive the seasonal ice regime. The recent and dramatic environmental changes have pushed scientists and engineers to improve the platforms and sensors rapidly.

8 Apr 2013

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Focus on Arctic Sea Ice: Current and Future States of a Diminished Sea Ice Cover

APL-UW polar scientists are featured in the March edition of the UW TV news magazine UW|360, where they discuss their research on the current and future states of a diminished sea ice cover in the Arctic.

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7 Mar 2012

The dramatic melting of Arctic sea ice over the past several summers has generated great interest and concern in the scientific community and among the public. Here, APL-UW polar scientists present their research on the current state of Arctic sea ice. A long-term, downward trend in sea ice volume is clear.

They also describe how the many observations they gather are used to improve computer simulations of global climate that, in turn, help us to asses the impacts of a future state of diminished sea ice cover in the Arctic.

This movie presentation was first seen on the March 2012 edition of UW|360, the monthly University of Washington Television news magazine.

Changing Freshwater Pathways in the Arctic Ocean

Freshening in the Canada Basin of the Arctic Ocean began in the 1990s. Polar scientist Jamie Morison and colleagues report new insights on the freshening based in part on Arctic-wide views from two satellite system.

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5 Jan 2012

The Arctic Ocean is a repository for a tremendous amount of river runoff, especially from several huge Russian rivers. During the spring of 2008, APL-UW oceanographers on a hydrographic survey in the Arctic detected major shifts in the amount and distribution of fresh water. The Canada basin had freshened, but had the entire Arctic Ocean?

Analysis of satellite records shows that salinity increased on the Russian side of the Arctic and decreased in the Beaufort Sea on the Canadian side. With an Arctic-wide view of circulation from satellite sensors, researchers were able to determine that atmospheric forcing had shifted the transpolar drift counterclockwise and driven Russian runoff east to the Canada Basin.

Oceanography from Space

In the North Atlantic and Arctic oceans observations by sensors on orbiting satellites are giving oceanographers insight to ocean processes on vast spatial and temporal scales.

1 Dec 2011


2000-present and while at APL-UW

Geophysical constraints on the Antarctic sea ice cover

Nghiem, S.V., I.G. Rigor, P. Clemente-Colón, G. Neumann, and P.P. Li, "Geophysical constraints on the Antarctic sea ice cover," Remote Sens. Environ., 181, 281-292, doi:10.1016/j.rse.2016.04.005, 2016.

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1 Aug 2016


The stark contrast between Arctic and Antarctic sea ice change is explained.

Observations show a frontal ice zone protecting and enhancing Antarctic sea ice.

The frontal ice zone is strongly influenced by winds and ocean fronts.

Antarctic winds are controlled by topography and ocean fronts by bathymetry.

Topography/bathymetry are stable geological factors constraining Antarctic sea ice.

Interannual variations of light-absorbing particles in snow on Arctic sea ice

Doherty, S.J., M. Steele, I. Rigor, and S.G. Warren, "Interannual variations of light-absorbing particles in snow on Arctic sea ice," J. Geophys. Res., 120, 11,391-11,400, doi:10.1002/2015JD024018, 2015.

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16 Nov 2015

Samples of snow on sea ice were collected in springtime of the 6 years 2008–2013 in the region between Greenland, Ellesmere Island, and the North Pole (82°N – 89°N, 0°W – 100°W). The meltwater was passed through filters, whose spectral absorption was then measured to determine the separate contributions by black carbon (BC) and other light-absorbing impurities. The median mixing ratio of BC across all years' samples was 4 ± 3 ng g-1, and the median fraction of absorption due to non-BC absorbers was 36 ± 11%. Variances represent both spatial and interannual variability; there was no interannual trend in either variable. The absorption Angstrom exponent, however, decreased with latitude, suggesting a transition from dominance by biomass-burning sources in the south to an increased influence by fossil-fuel-burning sources in the north, consistent with earlier measurements of snow in Svalbard and at the North Pole.

Seasonal evolution of melt ponds on Arctic sea ice

Webster, M.A., I.G. Rigor, D.K. Perovich, J.A. Richter-Menge, C.M. Polashenski, and B. Light, "Seasonal evolution of melt ponds on Arctic sea ice," J. Geophys. Res., 120, 5968-5982, doi:10.1002/2015JC011030, 2015.

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4 Sep 2015

The seasonal evolution of melt ponds has been well documented on multiyear and landfast first-year sea ice, but is critically lacking on drifting, first-year sea ice, which is becoming increasingly prevalent in the Arctic. Using 1 m resolution panchromatic satellite imagery paired with airborne and in situ data, we evaluated melt pond evolution for an entire melt season on drifting first-year and multiyear sea ice near the 2011 Applied Physics Laboratory Ice Station (APLIS) site in the Beaufort and Chukchi seas. A new algorithm was developed to classify the imagery into sea ice, thin ice, melt pond, and open water classes on two contrasting ice types: first-year and multiyear sea ice. Surprisingly, melt ponds formed ~3 weeks earlier on multiyear ice. Both ice types had comparable mean snow depths, but multiyear ice had 0–5 cm deep snow covering ~37% of its surveyed area, which may have facilitated earlier melt due to its low surface albedo compared to thicker snow. Maximum pond fractions were 53 ± 3% and 38 ± 3% on first-year and multiyear ice, respectively. APLIS pond fractions were compared with those from the Surface Heat Budget of the Arctic Ocean (SHEBA) field campaign. APLIS exhibited earlier melt and double the maximum pond fraction, which was in part due to the greater presence of thin snow and first-year ice at APLIS. These results reveal considerable differences in pond formation between ice types, and underscore the importance of snow depth distributions in the timing and progression of melt pond formation.

More Publications

Uncertainties of temperature measurements on snow-covered land and sea Ice from in situ and MODIS data during BROMEX

Hall, D.K., S. V. Nghiem, I.G. Rigor, and J.A. Miller, "Uncertainties of temperature measurements on snow-covered land and sea Ice from in situ and MODIS data during BROMEX," J. Appl. Meteor. Climatol., 54, 966-978, doi:10.1175/JAMC-D-14-0175.1, 2015.

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1 May 2015

The Bromine, Ozone, and Mercury Experiment (BROMEX) was conducted in March and April of 2012 near Barrow, Alaska, to investigate impacts of Arctic sea ice reduction on chemical processes. During BROMEX, multiple sensors were deployed to measure air and surface temperature. The uncertainties in temperature measurement on snow-covered land and sea ice surfaces were examined using in situ data and temperature measurements that were derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) and are part of the Terra and Aqua ice-surface temperature and land-surface temperature (LST) standard data products. Following an ~24-h cross-calibration study, two Thermochrons (small temperature-sensing devices) were deployed at each of three field sites: a sea ice site in the Chukchi Sea, a mixed-cover site, and a homogeneous tundra site. At each site, one Thermochron was shielded from direct sunlight and one was left unshielded, and they were placed on top of the snow or ice. The best agreement between the Thermochron- and MODIS-derived temperatures was found between the shielded Thermochrons and the Aqua MODIS LSTs, with an average agreement of 0.6° ± 2.0°C (sample size of 84) at the homogeneous tundra site. The results highlight some uncertainties associated with obtaining consistent air and surface temperature measurements in the harsh Arctic environment, using both in situ and satellite sensors. It is important to minimize uncertainties that could introduce biases in long-term temperature trends.

Interdecadal changes in snow depth on Arctic sea ice

Webster, M.A., I.G. Rigor, S.V. Nghiem, N.T. Kurtz, S.L. Farrell, D.K. Perovich, and M. Sturm, "Interdecadal changes in snow depth on Arctic sea ice," J. Geophys. Res., 119, 5395-5406, doi:10.1002/2014JC009985, 2014.

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13 Aug 2014

Snow plays a key role in the growth and decay of Arctic sea ice. In winter, it insulates sea ice from cold air temperatures, slowing sea ice growth. From spring into summer, the albedo of snow determines how much insolation is absorbed by the sea ice and underlying ocean, impacting ice melt processes. Knowledge of the contemporary snow depth distribution is essential for estimating sea ice thickness and volume, and for understanding and modeling sea ice thermodynamics in the changing Arctic. This study assesses spring snow depth distribution on Arctic sea ice using airborne radar observations from Operation IceBridge for 2009–2013. Data were validated using coordinated in situ measurements taken in March 2012 during the BRomine, Ozone, and Mercury EXperiment (BROMEX) field campaign. We find a correlation of 0.59 and root-mean-square error of 5.8 cm between the airborne and in situ data. Using this relationship and IceBridge snow thickness products, we compared the recent results with data from the 1937, 1954–1991 Soviet drifting ice stations. The comparison shows thinning of the snow pack, from 35.1 ± 9.4 cm to 22.2 ± 1.9 cm in the western Arctic, and from 32.8 ±D 9.4 cm to 14.5 ± 1.9 cm in the Beaufort and Chukchi seas. These changes suggest a snow depth decline of 37 ± 29% in the western Arctic and 56 ± 33% in the Beaufort and Chukchi seas. Thinning is negatively correlated with the delayed onset of sea ice freeze-up during autumn.

Effects of Mackenzie River discharge and bathymetry on sea ice in the Beaufort Sea

Nghiem, S.V., D.K. Hall, I.G. Rigor, P. Li, and G. Neumann, "Effects of Mackenzie River discharge and bathymetry on sea ice in the Beaufort Sea," Geophys. Res. Lett., 41, 873-879, doi:10.1002/2013GL058956, 2014.

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16 Feb 2014

Mackenzie River discharge and bathymetry effects on sea ice in the Beaufort Sea are examined in 2012 when Arctic sea ice extent hit a record low. Satellite-derived sea surface temperature revealed warmer waters closer to river mouths. By 5 July 2012, Mackenzie warm waters occupied most of an open water area about 316,000 km2. Surface temperature in a common open water area increased by 6.5°C between 14 June and 5 July 2012, before and after the river waters broke through a recurrent landfast ice barrier formed over the shallow seafloor offshore the Mackenzie Delta. In 2012, melting by warm river waters was especially effective when the strong Beaufort Gyre fragmented sea ice into unconsolidated floes. The Mackenzie and other large rivers can transport an enormous amount of heat across immense continental watersheds into the Arctic Ocean, constituting a stark contrast to the Antarctic that has no such rivers to affect sea ice.

Trends in Arctic sea ice and the role of atmospheric circulation

Ogi, M., and I.G. Rigor, "Trends in Arctic sea ice and the role of atmospheric circulation," Atmos. Sci. Lett., 14, 97-101, doi:10.1002/asl2.423, 2013.

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1 Apr 2013

The decrease in the September sea-ice extent over the Arctic has been accelerating since 1996. This study examined the contributions of atmospheric circulation anomalies and trends in winter and summer to changes in Arctic sea ice during the periods 1979–1996 and 1996–2010. In recent years, winter westerly winds over the Beaufort Sea and summer anticyclonic circulation over the Arctic toward the Fram Strait have contributed to accelerated decreases in sea ice over areas east of Europe and north of Alaska. In particular, recent strong anticyclonic circulation has caused an accelerating decrease in the Arctic sea ice in summer.

Seafloor control on sea ice

Nghiem, S.V., P. Clemente-Colón, I.G. Rigor, D.K. Hall, and G. Neumann, "Seafloor control on sea ice," Deep Sea Res. II, 77-80, 52-61, doi:10.1016/j.dsr2.2012.04.004, 2012.

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15 Nov 2012

The seafloor has a profound role in Arctic Sea ice formation and seasonal evolution. Ocean bathymetry controls the distribution and mixing of warm and cold waters, which may originate from different sources, thereby dictating the pattern of sea ice on the ocean surface. Sea ice dynamics, forced by surface winds, are also guided by seafloor features in preferential directions. Here, satellite mapping of sea ice together with buoy measurements are used to reveal the bathymetric control on sea ice growth and dynamics. Bathymetric effects on sea ice formation are clearly observed in the conformity between sea ice patterns and bathymetric characteristics in the peripheral seas. Beyond local features, bathymetric control appears over extensive regions of the sea ice cover across the Arctic Ocean. The large-scale conformity between bathymetry and patterns of different synoptic sea ice classes, including seasonal and perennial sea ice, is identified. An implication of the bathymetric influence is that the maximum extent of the total sea ice cover is relatively stable, as observed by scatterometer data in the decade of the 2000s, while the minimum ice extent has decreased drastically. Because of the geologic control, the sea ice cover can expand only as far as it reaches the seashore, the continental shelf break, or other pronounced bathymetric features in the peripheral seas. Since the seafloor does not change significantly for decades or centuries, sea ice patterns can be recurrent around certain bathymetric features, which, once identified, may help improve short-term forecast, seasonal outlook, and decadal prediction of the sea ice cover. Moreover, the seafloor can indirectly influence the cloud cover by its control on sea ice distribution, which differentially modulates the latent heat flux through ice covered and open water areas.

Recent changes in the dynamic properties of declining Arctic sea ice: A model study

Zhang, J., R. Lindsay, A. Schweiger, and I. Rigor, "Recent changes in the dynamic properties of declining Arctic sea ice: A model study," Geophys. Res. Lett., 39, doi:10.1029/2012GL053545, 2012.

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30 Oct 2012

Results from a numerical model simulation show significant changes in the dynamic properties of Arctic sea ice during 2007–2011 compared to the 1979–2006 mean. These changes are linked to a 33% reduction in sea ice volume, with decreasing ice concentration, mostly in the marginal seas, and decreasing ice thickness over the entire Arctic, particularly in the western Arctic. The decline in ice volume results in a 37% decrease in ice mechanical strength and 31% in internal ice interaction force, which in turn leads to an increase in ice speed (13%) and deformation rates (17%). The increasing ice speed has the tendency to drive more ice out of the Arctic. However, ice volume export is reduced because the rate of decrease in ice thickness is greater than the rate of increase in ice speed, thus retarding the decline of Arctic sea ice volume. Ice deformation increases the most in fall and least in summer. Thus the effect of changes in ice deformation on the ice cover is likely strong in fall and weak in summer. The increase in ice deformation boosts ridged ice production in parts of the central Arctic near the Canadian Archipelago and Greenland in winter and early spring, but the average ridged ice production is reduced because less ice is available for ridging in most of the marginal seas in fall. The overall decrease in ridged ice production contributes to the demise of thicker, older ice. As the ice cover becomes thinner and weaker, ice motion approaches a state of free drift in summer and beyond and is therefore more susceptible to changes in wind forcing. This is likely to make seasonal or shorter-term forecasts of sea ice edge locations more challenging.

Role of ice dynamics in anomalous ice conditions in the Beaufort Sea during 2006 and 2007

Hutchings, J.K., and I.G. Rigor, "Role of ice dynamics in anomalous ice conditions in the Beaufort Sea during 2006 and 2007," J. Geophys. Res., 117, doi:10.1029/2011JC007182, 2012.

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30 May 2012

A new record minimum in summer sea ice extent was set in 2007 and an unusual polynya formed in the Beaufort Sea ice cover during the summer of 2006. Using a combination of visual observations from cruises, ice drift, and satellite passive microwave sea ice concentration, we show that ice dynamics during preceding years included events that preconditioned the Beaufort ice pack for the unusual patterns of opening observed in both summers. Intrusions of first year ice from the Chukchi Sea to the Northern Beaufort, and increased pole-ward ice transport from the western Arctic during summer has led to reduced replenishment of multiyear ice, older than five years, in the western Beaufort, resulting in a younger, thinner ice pack in most of the Beaufort. We find ice younger than five years melts out completely by the end of summer, south of 76N. The 2006 unusual polynya was bounded to the south by an ice tongue composed of sea ice older than 5 years, and formed when first year and second year ice melted between 76N and the older ice to the south. In this paper we demonstrate that a recent shift in ice circulation patterns in the western Arctic preconditions the Beaufort ice pack for increased seasonal ice zone extent.

Field and satellite observations of the formation and distribution of Arctic atmospheric bromine above a rejuvenated sea ice cover

Nghiem, S.V., I.G. Rigor, A. Richter, et al., "Field and satellite observations of the formation and distribution of Arctic atmospheric bromine above a rejuvenated sea ice cover," J. Geophys. Res., 117, doi:10.1029/2011JD016268, 2012

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1 Mar 2012

Recent drastic reduction of the older perennial sea ice in the Arctic Ocean has resulted in a vast expansion of younger and saltier seasonal sea ice. This increase in the salinity of the overall ice cover could impact tropospheric chemical processes. Springtime perennial ice extent in 2008 and 2009 broke the half-century record minimum in 2007 by about one million km2. In both years seasonal ice was dominant across the Beaufort Sea extending to the Amundsen Gulf, where significant field and satellite observations of sea ice, temperature, and atmospheric chemicals have been made. Measurements at the site of the Canadian Coast Guard Ship Amundsen ice breaker in the Amundsen Gulf showed events of increased bromine monoxide (BrO), coupled with decreases of ozone (O3) and gaseous elemental mercury (GEM), during cold periods in March 2008. The timing of the main event of BrO, O3, and GEM changes was found to be consistent with BrO observed by satellites over an extensive area around the site. Furthermore, satellite sensors detected a doubling of atmospheric BrO in a vortex associated with a spiral rising air pattern. In spring 2009, excessive and widespread bromine explosions occurred in the same region while the regional air temperature was low and the extent of perennial ice was significantly reduced compared to the case in 2008. Using satellite observations together with a Rising-Air-Parcel model, we discover a topographic control on BrO distribution such that the Alaskan North Slope and the Canadian Shield region were exposed to elevated BrO, whereas the surrounding mountains isolated the Alaskan interior from bromine intrusion.

Changing Arctic Ocean freshwater pathways

Morison, J., R. Kwok, C. Peralta-Ferriz, M. Alkire, I. Rigor, R. Andersen, and M. Steele, "Changing Arctic Ocean freshwater pathways," Nature, 481, 66-70, doi:10.1038/nature10705, 2012.

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5 Jan 2012

Freshening in the Canada basin of the Arctic Ocean began in the 1990s and continued to at least the end of 2008. By then, the Arctic Ocean might have gained four times as much fresh water as comprised the Great Salinity Anomaly of the 1970s, raising the spectre of slowing global ocean circulation. Freshening has been attributed to increased sea ice melting and contributions from runoff, but a leading explanation has been a strengthening of the Beaufort High — a characteristic peak in sea level atmospheric pressure — which tends to accelerate an anticyclonic (clockwise) wind pattern causing convergence of fresh surface water. Limited observations have made this explanation difficult to verify, and observations of increasing freshwater content under a weakened Beaufort High suggest that other factors must be affecting freshwater content.

Here we use observations to show that during a time of record reductions in ice extent from 2005 to 2008, the dominant freshwater content changes were an increase in the Canada basin balanced by a decrease in the Eurasian basin. Observations are drawn from satellite data (sea surface height and ocean-bottom pressure) and in situ data. The freshwater changes were due to a cyclonic (anticlockwise) shift in the ocean pathway of Eurasian runoff forced by strengthening of the west-to-east Northern Hemisphere atmospheric circulation characterized by an increased Arctic Oscillation index. Our results confirm that runoff is an important influence on the Arctic Ocean and establish that the spatial and temporal manifestations of the runoff pathways are modulated by the Arctic Oscillation, rather than the strength of the wind-driven Beaufort Gyre circulation.

Modern dirty sea ice characteristics and sources: The role of anchor ice

Darby, D.A., W.B. Myers, M. Jakobsson, and I. Rigor, "Modern dirty sea ice characteristics and sources: The role of anchor ice," J. Geophys. Res., 116, doi:10.1029/2010JC006675, 2011.

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13 Sep 2011

Extensive dirty ice patches with up to 7 kg m-2 sediment concentrations in layers of up to 10 cm thickness were encountered in 2005 and 2007 in numerous areas across the central Arctic. The Fe grain fingerprint determination of sources for these sampled dirty ice floes indicated both Russian and Canadian sources, with the latter dominating. The presence of benthic shells and sea weeds along with thick layers (2-10 cm) of sediment covering 5-10 m2 indicates an anchor ice entrainment origin as opposed to suspension freezing for some of these floes. The anchor ice origin might explain the dominance of Canadian sources where only narrow flaw leads occur that would not favor suspension freezing as an entrainment process. Expandable clays, commonly used as an indicator of a Kara Sea origin for dirty sea ice, are present in moderately high percentages (>20%) in many circum-Arctic source areas, including the Arctic coasts of North America.

Some differences between the Russian and the North American coastal areas are found in clay mineral abundance, primarily the much higher abundance of chlorite in North America and the northern Barents Sea as opposed to the rest of the Russian Arctic. However, sea ice clay mineralogy matched many source areas, making it difficult to use as a provenance tool by itself. The bulk mineralogy (clay and non-clay) does not match specific sources possibly due to reworking of the sediment in dirty floes through summer melting or the failure to characterize all possible source areas.

Arctic perennial sea ice crash of the 2000s and its impacts

Nghiem, S., G. Neumann, P. Clemente-Colon, I. Rigor, and D. Perovich, "Arctic perennial sea ice crash of the 2000s and its impacts," Bionature2011: The Second International Conference on Bioenvironment, Biodiversity and Renewable Energies, 22-27 May, Venice, Italy, 38-42 (2011).

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22 May 2011

Satellite and surface observations show that half of the extent of perennial sea ice in the Arctic Ocean has been lost in the decade of 2000s. Perennial sea ice is the class of old and thick ice important for the stability of the Arctic environment. Perennial ice extent set the record low in 2008 and has remained low as seen in updated satellite scatterometer data and surface drifting buoy measurements in 2011. The drastic decline of Arctic sea ice is far exceeding the worst-case projections from climate models of the Intergovernmental Panel on Climate Change Fourth Assessment Report. The important role of the Polar Express phenomenon has been identified, indicating dynamic and thermodynamic effects are combined to expedite the loss of perennial sea ice. Consequently, major impacts include decreases in Arctic surface albedo, increases in absorbed insolation, facilitation of sea-route opening, and changes in tropospheric chemical processes such as bromine explosion, ozone depletion, and mercury deposition that impact the biosphere.

Sea ice response to an extreme negative phase of the Arctic Oscillation during winter 2009/2010

Stroeve, J.C., J. Maslanik, M.C. Serreze, I. Rigor, W. Meier, and C. Fowler, "Sea ice response to an extreme negative phase of the Arctic Oscillation during winter 2009/2010," Geophys. Res. Lett., 38, doi:10.1029/2010GL045662, 2011.

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29 Jan 2011

Based on relationships established in previous studies, the extreme negative phase of the Arctic Oscillation (AO) that characterized winter of 2009/2010 should have favored retention of Arctic sea ice through the 2010 summer melt season. The September 2010 sea ice extent nevertheless ended up as third lowest in the satellite record, behind 2007 and barely above 2008, reinforcing the long-term downward trend. This reflects pronounced differences in atmospheric circulation during winter of 2009/2010 compared to the mean anomaly pattern based on past negative AO winters, low ice volume at the start of the melt season, and summer melt of much of the multiyear ice that had been transported into the warm southerly reaches of the Beaufort and Chukchi seas.

Sensor-based profiles of the NO parameter in the central Arctic and southern Canada Basin: New insights regarding the cold halocline

Alkire, M.B., K.K. Falkner, J. Morison, R.W. Collier, C.K. Guay, R.A. Desiderio, I.G. Rigor, and M. McPhee, "Sensor-based profiles of the NO parameter in the central Arctic and southern Canada Basin: New insights regarding the cold halocline," Deep-Sea Res. Part I, 57, 1432-1443, doi:10.1016/j.dsr.2010.07.011, 2010.

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1 Nov 2010

Here we report the first optical, sensor-based profiles of nitrate from the central Makarov and Amundsen and southern Canada basins of the Arctic Ocean. These profiles were obtained as part of the International Polar Year program during spring 2007 and 2008 field seasons of the North Pole Environmental Observatory (NPEO) and Beaufort Gyre Exploration Program (BGEP). These nitrate data were combined with in-situ, sensor-based profiles of dissolved oxygen to derive the first high-resolution vertical NO profiles to be reported for the Arctic Ocean.

The focus of this paper is on the halocline layer that insulates sea ice from Atlantic water heat and is an important source of nutrients for marine ecosystems within and downstream of the Arctic. Previous reports based on bottle data have identified a distinct lower halocline layer associated with an NO minimum at about S=34.2 that was proposed to be formed initially in the Nansen Basin and then advected downstream. Greater resolution afforded by our data reveal an even more pronounced NO minimum within the upper, cold halocline of the Makarov Basin. Thus a distinct lower salinity source ventilated the Makarov and not the Amundsen Basin. In addition, a larger Eurasian River water influence overlies this halocline source in the Makarov. Observations in the southern Canada Basin corroborate previous studies confirming multiple lower halocline influences including diapycnal mixing between Pacific winter waters and Atlantic-derived lower halocline waters, ventilation via brine formation induced in persistent openings in the ice, and cold, O2-rich lower halocline waters originating in the Eurasian Basin. These findings demonstrate that continuous sensing of chemical properties promises to significantly advance understanding of the maintenance and circulation of the halocline.

Thinning and volume loss of the Arctic Ocean sea ice cover: 2003-2008

Kwok, R., G.F. Cunningham, M. Wensnahan, I. Rigor, H.J. Zwally, and D. Yi, "Thinning and volume loss of the Arctic Ocean sea ice cover: 2003-2008," J. Geophys. Res., 114, doi:10.1029/2009JC005312, 2009.

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7 Jul 2009

We present our best estimate of the thickness and volume of the Arctic Ocean ice cover from 10 Ice, Cloud, and land Elevation Satellite (ICESat) campaigns that span a 5-year period between 2003 and 2008. Derived ice drafts are consistently within 0.5 m of those from a submarine cruise in mid-November of 2005 and 4 years of ice draft profiles from moorings in the Chukchi and Beaufort seas. Along with a more than 42% decrease in multiyear (MY) ice coverage since 2005, there was a remarkable thinning of ~0.6 m in MY ice thickness over 4 years. In contrast, the average thickness of the seasonal ice in midwinter (~2 m), which covered more than two-thirds of the Arctic Ocean in 2007, exhibited a negligible trend. Average winter sea ice volume over the period, weighted by a loss of ~3000 km3 between 2007 and 2008, was ~14,000 km3. The total MY ice volume in the winter has experienced a net loss of 6300 km3 (>40%) in the 4 years since 2005, while the first-year ice cover gained volume owing to increased overall area coverage. The overall decline in volume and thickness are explained almost entirely by changes in the MY ice cover. Combined with a large decline in MY ice coverage over this short record, there is a reversal in the volumetric and areal contributions of the two ice types to the total volume and area of the Arctic Ocean ice cover. Seasonal ice, having surpassed that of MY ice in winter area coverage and volume, became the dominant ice type. It seems that the near-zero replenishment of the MY ice cover after the summers of 2005 and 2007, an imbalance in the cycle of replenishment and ice export, has played a significant role in the loss of Arctic sea ice volume over the ICESat record.

Summer retreat of Arctic sea ice: Role of summer winds

Ogi, M., I.G. Rigor, M.G. McPhee, and J.M. Wallace, "Summer retreat of Arctic sea ice: Role of summer winds," Geophys. Res. Lett., 35, doi:10.1029/2008GL035672, 2008.

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18 Dec 2008

The unprecedented retreat of first-year ice during summer 2007 was enhanced by strong poleward drift over the western Arctic induced by anomalously high sea-level pressure (SLP) over the Beaufort Sea that persisted throughout much of the summer. Comparison of the tracks of drifting buoys with monthly mean SLP charts shows a substantial Ekman drift. By means of linear regression analysis it is shown that Ekman drift during summer has played an important role in regulating annual minimum Arctic sea-ice extent in prior years as well. In combination, the preconditioning by events in prior years, as represented by an index of May multi-year ice, and current atmospheric conditions, as represented by an index of July–August–September SLP anomalies over the Arctic basin account for ~60% of the year-to-year variance of September sea-ice extent since 1979.

Mechanisms explaining anomalous ice conditions in the Beaufort Sea during 2006 and 2007

Hutchings, J., and I. Rigor, "Mechanisms explaining anomalous ice conditions in the Beaufort Sea during 2006 and 2007," Eos Trans. AGU, 89, Fall Meet. Suppl., abstract #C51A-0525, 2008.

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15 Dec 2008

Unusual Beaufort Sea ice conditions, in summers 2006 and 2007, are documented. Comparison of NASA team ice concentration estimates against in-situ observations show that NASA team concentrations, were 30% lower than in situ observations for flooded ice, and 10% lower for refrozen ice. We show that the drift of sea ice into the Beaufort and divergence precondition recent summer ice conditions. Intrusions of first year ice from the Chukchi Sea to the Northern Beaufort, and recent reduction in size of the Beaufort Gyre has led to reduced replenishment of older, multi-year ice in the western Beaufort, resulting in a younger, thinner ice pack in most of the Beaufort. However, during the Winter of 2006, an anomalous southward, then westward push of MY ice formed an ice tongue that survived the summer melt season. To the north of this tongue of MY ice, there is a trend over the last decade towards increasing late winter pack divergence. This leads to 20-30% thin ice area of melting out earlier in Summer, which may precondition the accelerated Summer ice loss observed in recent years. Late Winter opening in 2007 was two times greater than previously observed. Our results support the hypothesis (Perovich et al. 2008) that Summer 2007 thinning of MY ice was caused by an increase in solar absorption in the upper ocean due to lower sea ice concentration than normal, as the low ice concentration was partially driven by an anomalous opening event in the Beaufort Sea perennial ice pack in Spring 2007.

Recent state of arctic sea ice

Nghiem, S., I. Rigor, P. Clemente-Colon, D. Perovich, J. Richter-Menge, Y. Chao, G. Neumann, and M. Ortmeyer, "Recent state of arctic sea ice," Eos Trans. AGU, 89, Fall Meet. Suppl., abstract #C44A-01, 2008.

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15 Dec 2008

We present the recent state of Arctic sea ice including observations from 2008 in a context of a multi-decadal perspective. A new record has been set in the reduction of Arctic perennial sea ice extent this winter. As of 1 March 2008, the extent of perennial sea ice was reduced by one million km2 compared to that at the same time last year as observed by the NASA SeaWinds scatterometer on the QuikSCAT satellite (QSCAT). This decrease of perennial ice continues the precipitous declining trend observed in this decade. Furthermore, the perennial sea ice pattern change was deduced by buoy-based estimates with 50 years of data from drifting buoys and measurement camps to track sea ice movement around the Arctic Ocean. The combination of the satellite and surface data records confirms that the reduction of winter perennial ice extent broke the record in 2008 compared to data over the last half century.

In the winter, the loss of perennial ice extent was driven by winds that compressed the ice and transported it out of the Fram Strait and Nares Strait to warmer ocean waters at lower latitudes, where the ice melted very effectively. Another historical fact is that the boundary of perennial sea ice already crossed the North Pole (NP) in February 2008, leaving the area around the NP occupied by seasonal sea ice. This is the first time, not only from the satellite data record but also in the history of sea ice charting at the National Ice Center since the 1970's, that observations indicate the seasonal ice migration into the NP area so early in winter. In the Bering Sea by 12 March 2008, the sea ice edge reached to an extent that coincided with the continental shelf break, indicating bathymetric effects on the distribution of water masses along the Aleutian North Slope, Bering Slope, Anadyr and Kamchatka currents that governed the pattern of sea ice formation in this region. Moreover, QSCAT observations showed that, in the 2008 winter, seasonal ice occupied the Northern Sea Route, and most of two routes of the Northwest Passage, north and south of Victoria Island, which facilitated ice retreat and the opening of waterways this summer.

Most importantly, the shift from a perennial to a seasonal ice covered Arctic Ocean significantly decreases the overall surface albedo resulting in enhanced solar heat absorption in spring and summer, which further decreases the Arctic ice pack through the ice albedo feedback mechanism. In early September 2008, a major melt event occurred over a large region extending from the Beaufort Sea across the Kara Sea toward the Laptev Sea, with active melt areas encroaching in the NP vicinity. This melt event was caused by an advection of warm air from the south, which melted and pushed sea ice away at the same time. At that time, the total extent of Arctic sea ice was about 0.5 million km2 (size of Spain) larger than that at the same time last year.

The International Arctic Buoy Programme (IABP): A cornerstone of the Arctic Observing Network

Rigor, I.G., P. Clemente-Colon, and E. Hudson, "The International Arctic Buoy Programme (IABP): A cornerstone of the Arctic Observing Network," Proceedings, OCEANS 2008, 15-18 September, Quebec, Canada doi:10.1109/OCEANS.2008.5152136 (IEEE, 2008).

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15 Sep 2008

The Arctic has undergone dramatic changes in weather, climate and environment. It should be noted that many of these changes were first observed and studied using data from the IABP (http://iabp.apl.washington.edu). For example, IABP data were fundamental to Walsh et al. (1996) showing that atmospheric pressure has decreased (Figure 1), Rigor et al. (2000) showing that air temperatures have increased (Figure 2), and to Proshutinsky and Johnson (1997); Steele and Boyd, (1998); Kwok, (2000); and Rigor et al. (2002) showing that the clockwise circulation of sea ice and the ocean has weakened (Figure 1). All these results relied heavily on IABP data.

Reduced ice thickness in Arctic Transpolar Drift favor rapid ice retreat

Haas, C., A. Pfaffling, S. Hendriks, L. Rabenstein, J.-L. Etienne, and I. Rigor, "Reduced ice thickness in Arctic Transpolar Drift favor rapid ice retreat," Geophys. Res. Lett., 35, doi:10.1029/2008GL034457, 2008.

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3 Sep 2008

Helicopter-borne electromagnetic sea ice thickness measurements were performed over the Transpolar Drift in late summers of 2001, 2004, and 2007, continuing ground-based measurements since 1991. These show an ongoing reduction of modal and mean ice thicknesses in the region of the North Pole of up to 53 and 44%, respectively, since 2001. A buoy derived ice age model showed that the thinning was mainly due to a regime shift from predominantly multi- and second-year ice in earlier years to first-year ice in 2007, which had modal and mean summer thicknesses of 0.9 and 1.27 m. Measurements of second-year ice which still persisted at the North Pole in April 2007 indicate a reduction of late-summer second-year modal and mean ice thicknesses since 2001 of 20 and 25% to 1.65 and 1.81 m, respectively. The regime shift to younger and thinner ice could soon result in an ice free North Pole during summer.

Climate Change: Developments in the Arctic

Rigor, I.G., "Climate Change: Developments in the Arctic," Proceedings, Alaska Forum on the Environment, 11-15 February, Anchorage, AK (2008).

15 Feb 2008

An assessment of arctic sea ice forecasts on seasonal time scales

Rigor, I.G., T. Arbetter, M. Ortmeyer, P. Clemente-Colon, and J. Woods, "An assessment of arctic sea ice forecasts on seasonal time scales," Proceedings, Am. Meteorol. Soc. Meet., 20-24 January, New Orleans, LA (2008).

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23 Jan 2008

The extent of arctic sea ice during summer has declined to record minima during the past decade. Four of the lowest minima in the last 100 years were observed during this period, with the new record minimum set in September 2007. Can we predict these minima?

The ability to predict Arctic sea ice conditions has many important social and economic consequences. Many species and cultures depend on the sea ice for habitat and subsistence. The lack of sea ice in an area along the coast may allow ocean waves to fetch up higher, producing stronger storm surges which may threaten low elevation coastal towns. The extent of Arctic sea ice affects navigation from the Atlantic to the Pacific through the Arctic along the Northern Sea Route and Northwest Passage, which are as much as 60% shorter than the conventional routes from Europe to the west coast of the U.S. or Japan. And the decline of sea ice may increase access to natural resources, e.g. the U.S. Geological Survey estimates that the Arctic may store as much as 25% of the world's petroleum reserves.

Operational prediction of sea ice conditions for the United States (and the world) is provided by the National/Naval Ice Center (NIC), which is an interagency collaboration between the Navy, National Oceanographic and Atmospheric Administration (NOAA), and the Coast Guard. The NIC currently provides 2-week global ice analyses and 30-day forecasts of sea ice conditions. However, some of the NIC's procedures are based on studies dating back to the 1970's, and recent advances in our understanding of Arctic climate provide some insight into how we may be able to improve our ability to predict Arctic sea ice conditions on weekly to seasonal time scales. The decline of sea ice may be attributed to global warming (e.g. the Arctic Climate Impacts Assessment Report 2004), but this decline may also be attributed to a change in the wind driven circulation of Arctic sea ice. In a series of papers, we showed that the prior winter Arctic Oscillation (AO) conditions explained most of the trends in summer sea ice extent in the Eurasian sector of the Arctic Ocean (Rigor et al. 2002), while in the Alaskan sector the recent extreme minima may be due to the drift of younger, thinner ice towards the Alaskan coast during the recent predominance of high to moderate AO conditions (Rigor and Wallace, 2004). Since it takes a number of years for sea ice to age and thicken, these results imply that we may be able to predict the extent of summer sea ice months in advance.

This projects aims to transition research on arctic sea ice variability using observations from the International Arctic Buoy Programme into an operational sea ice forecast by the NIC as part of the NOAA's Transition of Research Applications to Climate Services program.

During the past two years we have observed an increased transport of the older, thicker perennial sea ice across the Arctic Ocean to be exported through Fram Strait into the Greenland Sea. This transport has left much of the Arctic Ocean covered by thinner, first-year sea ice which has less mass to survive the summer melt, especially in the Eurasian sector of the Arctic Ocean. Given these observations we predict that this summer will set a new record minimum in summer sea ice extent in the Arctic, and plan to discuss the skill of this forecast.

Rapid reduction of Arctic Perennial sea ice

Nghiem, S.V., I.G. Rigor, D.K. Perovich, P. Clemente-Colon, J.W. Weatherly, and G. Neumann, "Rapid reduction of Arctic Perennial sea ice," Geophys. Res. Lett., 34, doi:10.1029/2007GL031138, 2007.

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4 Oct 2007

The extent of Arctic perennial sea ice, the year-round ice cover, was significantly reduced between March 2005 and March 2007 by 1.08 x 106 km2, a 23% loss from 4.69 x 106 km2 to 3.61 x 106 km2, as observed by the QuikSCAT/SeaWinds satellite scatterometer (QSCAT). Moreover, the buoy-based Drift-Age Model (DM) provided long-term trends in Arctic sea-ice age since the 1950s. Perennial-ice extent loss in March within the DM domain was noticeable after the 1960s, and the loss became more rapid in the 2000s when QSCAT observations were available to verify the model results. QSCAT data also revealed mechanisms contributing to the perennial-ice extent loss: ice compression toward the western Arctic, ice loading into the Transpolar Drift (TD) together with an acceleration of the TD carrying excessive ice out of Fram Strait, and ice export to Baffin Bay. Dynamic and thermodynamic effects appear to be combining to expedite the loss of perennial sea ice.

The return of Pacific waters to the upper layers of the central Arctic Ocean

Alkire, M.B., and K.K. Falkner, I. Rigor, M. Steele, and J. Morison, "The return of Pacific waters to the upper layers of the central Arctic Ocean," Deep-Sea Res. I, 54, 1509-1529, doi:10.1016/j.dsr.2007.06.004, 2007.

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1 Sep 2007

Temperature, salinity, and chemical measurements, including the nutrients silicic acid, nitrate, nitrite, ammonium, and phosphate, the oxygen isotopic composition of seawater, and barium concentrations were obtained from the central Arctic Ocean along transects radiating from the North Pole in early spring, 2000–2006. Stations that were reoccupied over this time period were grouped into five regions: from Ellesmere Island, (1) north along 70°W and (2) northwest along 90°W; near the North Pole, (3) on the Amundsen Basin flank and (4) directly over the Lomonosov Ridge; (5) through the Makarov Basin along 170–180°W. These regions had been shown by others to have undergone marked changes in water-mass assemblies in the early 1990s, but our time series tracer hydrographic data indicate a partial return of Pacific origin water within the mixed layer and the upper halocline layers beginning in 2003–2004. Back-trajectories derived from satellite-tracked ice buoys for these stations indicate that the upper levels of Pacific water in the central Arctic in 2004–2006 transited westward from the Bering Strait along the Siberian continental slope into the East Siberian Sea before entering the Transpolar Drift Stream (TPD). By 2004, the TPD shifted back from an alignment over the Alpha-Mendeleev Ridge toward the Lomonosov Ridge, as was characteristic prior to the early 1990s. At most stations occupied in 2006, a decrease in the Pacific influence was observed, both in the mixed layer and in the upper halocline, which suggests the Canadian branch of the TPD was shifting back toward North America. Clearly the system is more variable than has been previously appreciated.

Autumn atmospheric preconditioning for interannual variability of wintertime sea ice in the Okhotsk Sea

Sasaki, Y.N., Y. Katagiri, S. Minobe, and I.G. Rigor, "Autumn atmospheric preconditioning for interannual variability of wintertime sea ice in the Okhotsk Sea," J. Oceanogr., 63, 255-265, 2007.

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1 Feb 2007

Relations in year-to-year variability between wintertime Sea-Ice Concentrations (SICs) in the Okhotsk Sea and atmospheric anomalies consisting of zonal and meridional 1000-hPa wind speeds and 850-hPa air temperatures are studied using a singular value decomposition analysis. It is revealed that the late autumn (October-November) atmospheric conditions strongly influence sea-ice variability from the same season (late autumn) through late winter (February-March), in which sea-ice extent is at its maximum. The autumn atmospheric conditions for the positive sea-ice anomalies exhibit cold air temperature anomalies over the Okhotsk Sea and wind anomalies blowing into the Okhotsk Sea from Siberia. These atmospheric conditions yield anomalous ocean-to-atmosphere heat fluxes and cold sea surface temperature anomalies in the Okhotsk Sea. Hence, these results suggest that the atmospheric conditions affect the sea-ice through heat anomalies stored in sea-ice and oceanic fields. The late autumn atmosphere conditions are related to large 700-hPa geopotential height anomalies over the Bering Sea and northern Eurasia, which are related to a stationary Rossby wave propagation over the North Pacific and that from the North Atlantic to Eurasia, respectively. In addition, the late autumn atmospheric preconditioning also plays an important role in the decreasing trend in the Okhotsk sea-ice extent observed from 1980 to the mid-1990s. Based on the lagged sea-ice response to the late autumn atmosphere, a simple seasonal prediction scheme is proposed for the February-March sea-ice extent using four-month leading atmospheric conditions. This scheme explains 45% of the variance of the Okhotsk sea-ice extent.

Ice mass balance buoys: A tool for measuring and attributing changes in the thickness of Arctic sea ice cover

Richter-Menge, J.A., D.K. Perovich, B.C. Elder, K. Claffey, I. Rigor, and M. Ortmeyer, "Ice mass balance buoys: A tool for measuring and attributing changes in the thickness of Arctic sea ice cover," Ann. Glaciol. 44, 205-210, 2006.

1 Nov 2006

The cryosphere and climate change: Perspectives on the Arctic's shrinking sea ice cover

Serreze, M.C., and I.G. Rigor, "The cryosphere and climate change: Perspectives on the Arctic's shrinking sea ice cover," Glacier Science and Environmental Change, edited by P. Knight, 120-125 (Malden, MA: Blackwell Publishing Ltd., 2006).

30 Jan 2006

Sediment transport by sea ice in the Chukchi and Beaufort seas: Increasing importance due to changing ice conditions?

Eicken, H., R. Gradinger, A. Gaylord, A. Mahoney, I. Rigor, and H. Melling, "Sediment transport by sea ice in the Chukchi and Beaufort seas: Increasing importance due to changing ice conditions?" Deep-Sea Res. II, 52, 3281-3302, doi:10.1016/j.dsr2.2005.10.006, 2005

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30 Dec 2005

Sediment-laden sea ice is widespread over the shallow, wide Siberian Arctic shelves, with off-shelf export from the Laptev and East Siberian Seas contributing substantially to the Arctic Ocean's sediment budget. By contrast, the North American shelves, owing to their narrow width and greater water depths, have not been deemed as important for basin-wide sediment transport by sea ice. Observations over the Chukchi and Beaufort shelves in 2001/02 revealed the widespread occurrence of sediment-laden ice over an area of more than 100,000 km2 between 68 and 74°N and 155 and 170°W. Ice stratigraphic studies indicate that sediment inclusions were associated with entrainment of frazil ice into deformed, multiple layers of rafted nilas, indicative of a flaw-lead environment adjacent to the landfast ice of the Chukchi and Beaufort Seas. This is corroborated by buoy trajectories and satellite imagery indicating entrainment in a coastal polynya in the eastern Chukchi Sea in February of 2002 as well as formation of sediment-laden ice along the Beaufort Sea coast as far eastward as the Mackenzie shelf. Moored upward-looking sonar on the Mackenzie shelf provides further insight into the ice growth and deformation regime governing sediment entrainment. Analysis of Radarsat Synthetic Aperture (SAR) imagery in conjunction with bathymetric data help constrain the water depth of sediment resuspension and subsequent ice entrainment (>20 m for the Chukchi Sea).

Sediment loads averaged at 128 t km-2, with sediment occurring in layers of roughly 0.5 m thickness, mostly in the lower ice layers. The total amount of sediment transported by sea ice (mostly out of the narrow zone between the landfast ice edge and waters too deep for resuspension and entrainment) is at minimum 4 x 106 t in the sampling area and is estimated at 5–8 x 106 t over the entire Chukchi and Beaufort shelves in 2001/02, representing a significant term in the sediment budget of the western Arctic Ocean. Recent changes in the Chukchi and Beaufort Sea ice regimes (reduced summer minimum ice extent, ice thinning, reduction in multi-year ice extent, altered drift paths and mid-winter landfast ice break-out events) have likely resulted in an increase of sediment-laden ice in the area. Apart from contributing substantially to along- and across-shelf particulate flow, an increase in the amount of dirty ice significantly impacts (sub-)ice algal production and may enhance the dispersal of pollutants.

International Arctic Buoy Programme Data Report: 1 January 2003 - 31 December 2003

Ortmeyer, M., and I. Rigor, "International Arctic Buoy Programme Data Report: 1 January 2003 - 31 December 2003," APL-UW TM 2-04, June 2004.

30 Jun 2004

Variations in the age of Arctic sea-ice and summer sea-ice extent

Rigor, I.G., and J.M. Wallace, "Variations in the age of Arctic sea-ice and summer sea-ice extent," Geophys. Res. Lett., 31, L09401, 10.1029/2004GL019492, 2004.

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8 May 2004

Three of the past six summers have exhibited record low sea-ice extent on the Arctic Ocean. These minima may have been dynamically induced by changes in the surface winds. Based on results of a simple model that keeps track of the age of ice as it moves about on the Arctic Ocean, we show that the areal coverage of thick multi-year ice decreased precipitously during 1989–1990 when the Arctic Oscillation was in an extreme "high index" state, and has remained low since that time. Under these conditions, younger, thinner ice anomalies recirculate back to the Alaskan coast more quickly, decreasing the time that new ice has to ridge and thicken before returning for another melt season. During the 2002 and 2003 summers this anomalously younger, thinner ice was advected into Alaskan coastal waters where extensive melting was observed, even though temperatures were locally colder than normal. The age of sea-ice explains more than half of the variance in summer sea-ice extent.

International Arctic Buoy Programme Data Report: 1 January 2002 - 31 December 2002

Ortmeyer, M. and I. Rigor, "International Arctic Buoy Programme Data Report: 1 January 2002 - 31 December 2002," APL-UW TM 5-03, May 2003

30 May 2003

Response of sea ice to the Arctic Oscillation

Rigor, I.G., J.M. Wallace, and R.I. Colony, "Response of sea ice to the Arctic Oscillation," J. Climate, 15, 2648-2663, 2002.

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1 Sep 2002

Data collected by the International Arctic Buoy Programme from 1979 to 1998 are analyzed to obtain statistics of sea level pressure (SLP) and sea ice motion (SIM). The annual and seasonal mean fields agree with those obtained in previous studies of Arctic climatology. The data show a 3-hPa decrease in decadal mean SLP over the central Arctic Ocean between 1979–88 and 1989–98. This decrease in SLP drives a cyclonic trend in SIM, which resembles the structure of the Arctic Oscillation (AO).

Regression maps of SIM during the wintertime (January–March) AO index show 1) an increase in ice advection away from the coast of the East Siberian and Laptev Seas, which should have the effect of producing more new thin ice in the coastal flaw leads; 2) a decrease in ice advection from the western Arctic into the eastern Arctic; and 3) a slight increase in ice advection out of the Arctic through Fram Strait. Taken together, these changes suggest that at least part of the thinning of sea ice recently observed over the Arctic Ocean can be attributed to the trend in the AO toward the high-index polarity.

Rigor et al. showed that year-to-year variations in the wintertime AO imprint a distinctive signature on surface air temperature (SAT) anomalies over the Arctic, which is reflected in the spatial pattern of temperature change from the 1980s to the 1990s. Here it is shown that the memory of the wintertime AO persists through most of the subsequent year: spring and autumn SAT and summertime sea ice concentration are all strongly correlated with the AO index for the previous winter. It is hypothesized that these delayed responses reflect the dynamical influence of the AO on the thickness of the wintertime sea ice, whose persistent "footprint" is reflected in the heat fluxes during the subsequent spring, in the extent of open water during the subsequent summer, and the heat liberated in the freezing of the open water during the subsequent autumn.

A freshwater jet on the east Greenland shelf

Bacon, S., G. Reverdin, I.G. Rigor, and H.M. Snaith, "A freshwater jet on the east Greenland shelf," J. Geophys. Res., 107, 10.1029/2001JC000935, 2002.

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10 Jul 2002

In August 1997, RRS Discovery cruise 230 (World Ocean Circulation Experiment (WOCE) section A25) ran a hydrographic section into Cape Farewell on the southern tip of Greenland. The closest approach to the shore was 2 nm in a water depth of 160 m over the east Greenland shelf. Analysis of the hydrographic data (conductivity-temperature-depth (CTD), vessel-mounted acoustic Doppler current profiler, and thermosalinograph) has revealed a current flowing southwestward, ~15 km wide, 100 m deep, and centered ~10 km offshore. We believe it to be driven by meltwater runoff from Greenland. This feature, which we call the East Greenland Coastal Current (EGCC), carries a little less than 1 Sv (106 m3 s-1) with peak current speeds of ~1 m s-1 at the surface. The center of the EGCC lies on a salinity front with maximum salinity contrast ~4 practical salinity units (psu) between coast and shelf break and between surface and bottom. A spot value of freshwater transport is 0.06 Sv (1800 km3 yr-1), which is equivalent to ~30% of the Arctic freshwater gain. The presence of the EGCC and its continuity up the east Greenland coast as far as Denmark Strait is confirmed in satellite sea surface temperature images and surface drifter tracks. We estimate the sensitivity of its freshwater flux to changes in melt season mean surface air temperature to be >25% per 1°C.

International Arctic Buoy Programme Data Report: 1 January 2001 - 31 December 2001

Rigor, I. and M. Ortmeyer, "International Arctic Buoy Programme Data Report: 1 January 2001 - 31 December 2001," APL-UW TM 6-02, May 2002.

30 May 2002

International Arctic Buoy Programme Data Report, 1 January 2000 - 31 December 2000

Rigor, I., and M. Ortmeyer, "International Arctic Buoy Programme Data Report, 1 January 2000 - 31 December 2000," APL-UW TM 4-01, April 2001.

1 Apr 2001

International Arctic Buoy Programme Data Report 1 January 1998 - 31 December 1998

Rigor, I., and M. Ortmeyer, "International Arctic Buoy Programme Data Report 1 January 1998 - 31 December 1998," APL-UW TM 3-00, June 2000.

1 Jun 2000

International Arctic Buoy Programme Data Report 1 January 1999 - 31 December 1999

Rigor, I., and M. Ortmeyer, "International Arctic Buoy Programme Data Report 1 January 1999 - 31 December 1999," APL-UW TM 6-00, June 2000.

1 Jun 2000

Variations in surface air temperatures over the Arctic Ocean from 1979 to 1997

Rigor, I., R. Colony, and S. Martin, "Variations in surface air temperatures over the Arctic Ocean from 1979 to 1997," J. Climate, 13, 896-914, 2000.

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1 Mar 2000

The statistics of surface air temperature observations obtained from buoys, manned drifting stations, and meteorological land stations in the Arctic during 1979–97 are analyzed. Although the basic statistics agree with what has been published in various climatologies, the seasonal correlation length scales between the observations are shorter than the annual correlation length scales, especially during summer when the inhomogeneity between the ice-covered ocean and the land is most apparent. During autumn, winter, and spring, the monthly mean correlation length scales are approximately constant at about 1000 km; during summer, the length scales are much shorter, that is, as low as 300 km. These revised scales are particularly important in the optimal interpolation of data on surface air temperature (SAT) and are used in the analysis of an improved SAT dataset called International Arctic Buoy Programme/Polar Exchange at the Sea Surface (IABP/POLES). Compared to observations from land stations and the Russian North Pole drift stations, the IABP/POLES dataset has higher correlations and lower rms errors than previous SAT fields and provides better temperature estimates, especially during summer in the marginal ice zones. In addition, the revised correlation length scales allow data taken at interior land stations to be included in the optimal interpretation analysis without introducing land biases to grid points over the ocean. The new analysis provides 12-h fields of air temperatures on a 100-km rectangular grid for all land and ocean areas of the Arctic region for the years 1979–97.

The IABP/POLES dataset is then used to study spatial and temporal variations in SAT. This dataset shows that on average melt begins in the marginal seas by the first week of June and advances rapidly over the Arctic Ocean, reaching the pole by 19 June, 2 weeks later. Freeze begins at the pole on 16 August, and the freeze isotherm advances more slowly than the melt isotherm. Freeze returns to the marginal seas a month later than at the pole, on 21 September. Near the North Pole, the melt season length is about 58 days, while near the margin, the melt season is about 100 days. A trend of +1°C (decade)-1 is found during winter in the eastern Arctic Ocean, but a trend of –1°C (decade-1 is found in the western Arctic Ocean. During spring, almost the entire Arctic shows significant warming trends. In the eastern Arctic Ocean this warming is as much as 2°C (decade)-1. The spring warming is associated with a trend toward a lengthening of the melt season in the eastern Arctic. The western Arctic, however, shows a slight shortening of the melt season. These changes in surface air temperature over the Arctic Ocean are related to the Arctic Oscillation, which accounts for more than half of the surface air temperature trends over Alaska, Eurasia, and the eastern Arctic Ocean but less than half in the western Arctic Ocean.

In The News

Fra Aalborg til Nordpolen: Paa mission for NASA (with video)

TV2 Nord (Denmark), Lasse Dieckmann

Ice-hardened buoys, known as Air Expendable Ice Beacons (AXIB), were deployed in the Arctic Ocean near the North Pole from a Royal Danish Airforce C-130 aircraft flying out of Thule Air Base in Greenland.

13 Sep 2017

U.S. Navy leads international effort to deploy buoys into the Arctic Ocean

U.S. Navy News Service

Air-Deployable Expendable Ice Buoys are deployed in the high Arctic near the North Pole from a Royal Danish Air Force C-130 aircraft operating out of Thule Air Force Base in Greenland, as part of the International Arctic Buoy Program (IABP).

12 Sep 2017

Scientific research meets Coast Guard training on mission through Arctic skies

Alaska Dispatch News, Kamala Kelkar

Rigor is here from Seattle to ensure his special meteorological tool is dropped into the sea with immaculate precision. To help with these deployments and to help train its crew, the Coast Guard makes a practice of bringing scientists aboard its Arctic Domain Awareness flight — especially the University of Washington team, which has been accompanying the Coast Guard for years.

20 Jul 2015

More News Items

Study: Thinning Arctic snow could alter North Pole ecosystem


Researchers at the University of Washington and NASA confirmed their findings by combining data collected by ice bouys and aircraft with historic data from the late 1950s to the 90s.

14 Aug 2014

Snow has thinned on Arctic sea ice

UW News and Information, Hannah Hickey

From research stations drifting on ice floes to high-tech aircraft radar, scientists have been tracking the depth of snow that accumulates on Arctic sea ice for almost a century. Now that people are more concerned than ever about what is happening at the poles, research led by the University of Washington and NASA confirms that snow has thinned significantly in the Arctic, particularly on sea ice in western waters near Alaska.

13 Aug 2014

Ground Zero for Climate Change in Alaska

PBS News Hour, April Brown

More than 300 miles north of the Arctic Circle, Alaska%u2019s North Slope is ground zero for global climate change. NewsHour producer April Brown reports the melting ice has opened up opportunity for shipping and other development — industry that could be catastrophic for the way of life of residents.

19 Sep 2013

In Alaska, melting ice could erode way of life

PBS News Hour, Mike Fritz

Temperatures in the Arctic are warming twice as fast as any other place on the planet. Ignatius Rigor, an expert on sea ice, has been coming to Barrow, Alaska, for years. He says that because average winter temperatures in the Arctic have risen sharply over the last few decades, the total volume of sea ice is down to less than 40 percent of what it was in the 1980s.

17 Sep 2013

Alaska's disappearing ice

BBC World News, Stephen Sackur

Scientists are constantly monitoring the thickness and extent of the Arctic's ice cover. Their results show the ice is getting thinner and younger. Ice that lasts for more than three or four years is now a rarity. HARDtalk's Stephen Sackur took a ride on the Arctic ice and spoke to Ignatius Rigor, who predicts the rate of climate change could increase.

30 Jul 2013

Scientists chuck instruments off planes into cracks in Arctic sea ice

NBCNews.com, Charles Q. Choi

As sea ice disappears in the Arctic Ocean, the U.S. Coast Guard is teaming with scientists to explore this new frontier by deploying scientific equipment through cracks in the ice from airplanes hundreds of feet in the air.

10 Oct 2012

UW scientists team with Coast Guard to explore ice-free Arctic Ocean

UW New and Information, Nancy Gohring

A new partnership has evolved for the Coast Guard and University of Washington scientists since disappearing Arctic ice has opened vast new frontiers.

2 Oct 2012

Explore the polar ice caps at the Pacific Science Center

The Seattle Times/KING 5 News, Christine Johnson

University of Washington's Applied Physics Laboratory has teamed up with the Pacific Science Center for four days of demonstrations, exhibits and talks aimed at school children, families, and people interested in learning more about the poles. Polar Science Weekend will feature over ninety scientists that work in some of the most remote and challenging places on earth.

2 Mar 2012

Warming theory holds, climate experts insist

Spokane Spokesman-Review, Renee Schoof

Cold, snowy winters don't negate science. Ignatius Rigor notes, "Even in a warming world we will still have natural oscillations like day and night, winter and summer, and in this case El Nino and La Nina."

30 Jan 2011

Measuring the melting arctic sea ice

Miller-McCune, Bruce Dorminey

A new satellite will measure to the centimeter just how far gone, or going, the Arctic ice cap really is.

4 Jul 2010

New light shed on North Pole ice trends

The New York Times, Andrew C. Revkin

The sun rose over the horizon at the North Pole last weekend and the six-month "day" just began there, making this a good time to check in on ice and climate trends up north. Ignatius Rigor weighs in that sea ice is conditioned for a colder, and more extensive sea ice during the next couple of seasons.

22 Mar 2010

Cold arctic pressure pattern nearly off chart

The New York Times, Andrew C. Revkin

Several specialists studying Arctic sea ice told me that there's a good chance that, if current conditions persist, the ice this spring could be in better shape than it has been over the last few years. The polar pressure pattern, called the Arctic Oscillation, is deep in its negative phase at the moment - a depth not seen since the 1980s, according to Ignatius Rigor of the Polar Science Center.

4 Jan 2010

Changes in Arctic sea ice coverage from 1978 to 2008

Guardian Unlimited (London)

The Guardian displays a time-lapse map of changes in Arctic sea ice coverage from 1978 to 2008, developed by Ignatius Rigor at the Applied Physics Lab.

15 Oct 2009

North Pole ever closer to having no ice

The Seattle Post-Intelligencer, Lisa Stiffler

For Arctic expert Ignatius Rigor, this is one bet he'd rather lose. He figured he was safe in his wager with fellow polar gurus that the area of ice would have shrunk to a record low this summer, beating last year's astonishing disappearing act.

16 Sep 2008

Low levels of Arctic sea ice signal global warming's advance

McClatchy Newspapers, Renee Schoof

Ignatius G. Rigor, a scientist who researches Arctic sea ice and the atmosphere at the Polar Science Center, said he still thinks there's a chance this year's minimum will hit a new low.

9 Sep 2008

Shrinking Arctic Ocean sea ice signals climate change

The Christian Science Monitor, Peter N. Spotts

Global warming may have accelerated the irreversible loss of ice shelves that are thousands of years old, say scientists.

4 Sep 2008

Skeptics on human climate impact seize on cold spell

The New York Times, Andrew C. Revkin

The world has seen some extraordinary winter conditions in both hemispheres over the past year. It is no wonder that some scientists, opinion writers, political operatives and other people who challenge warnings about dangerous human-caused global warming have jumped on this as a teachable moment.

3 Mar 2008

UW climatologist says sea ice likely to continue shrinking

KOMO TV News, Scott Sistek

Ignatius Rigor, speaking at the Alaska Forum on the Environment, says Arctic sea ice next summer may shrink to an amount even smaller than last year's record-setting low area.

12 Feb 2008

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