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Roger Andersen

Principal Mathematician

Email

roger@apl.washington.edu

Phone

206-543-1258

Biosketch

Roger Andersen has made 35 trips to the polar regions for scientific research since joining the Polar Science Center in 1975, when it was the Arctic Ice Dynamics Joint Experiment. His current projects include the North Pole Environmental Observatory and the Freshwater Switchyard of the Arctic Ocean.

Department Affiliation

Polar Science Center

Education

B.A. Mathematics, Washington State University, 1970

M.S. Atmospheric Science, University of Washington, 1973

Publications

2000-present and while at APL-UW

Sea state bias of ICESat in the subarctic seas

Morison, J., R. Kwok, S. Dickinson, D. Morison, C. Peralta-Ferriz, and R. Andersen, "Sea state bias of ICESat in the subarctic seas," IEEE Geosci. Remote Sens. Lett., 15, 1144-1148, doi:10.1109/LGRS.2018.2834362, 2018.

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1 Aug 2018

The fine spatial resolution of laser altimeters makes them potentially valuable to oceanography studying features at mesoscale, close to land, and in the marginal ice zone. To fulfill this promise, we must understand laser sea state bias (SSB). SSB occurs in the measurement of sea surface height in the presence of waves when the altimeter observations are preferentially influenced by particular parts (e.g., wave troughs) of the wave-covered surface. Radar altimeters have received considerable attention relating radar SSB to wave properties and wind speed. Comparatively, little attention has been devoted to the SSB of laser altimeters, and the studies of laser SSB which have been done have led to indeterminate or ambiguous results even as to sign. Here, we find that to make changes in satellite dynamic ocean topography (DOT) from the Ice, Clouds, and Land Elevation Satellite (ICESat) period, 2004–2009, to the CryoSat-2 period, 2011–2015, consistent with hydrography plus ocean bottom pressure in the subarctic Greenland and Norwegian seas, we need to correct the ICESat DOT for SSB. On average, ICESat SSB is –18% of significant wave height in excess of 1.7 m.

Arctic ice–ocean coupling and gyre equilibration observed with remote sensing

Dewey, S., J. Morison, R. Kwok, S. Dickinson, D. Morison, and R. Andersen, "Arctic ice–ocean coupling and gyre equilibration observed with remote sensing," Geophys. Res. Lett., 45, 1499-1508, doi:10.1002/2017GL076229, 2018.

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16 Feb 2018

Model and observational evidence has shown that ocean current speeds in the Beaufort Gyre have increased and recently stabilized. Because these currents rival ice drift speeds, we examine the potential for the Beaufort Gyre's shift from a system in which the wind drives the ice and the ice drives a passive ocean to one in which the ocean often, in the absence of high winds, drives the ice. The resultant stress exerted on the ocean by the ice and the resultant Ekman pumping are reversed, without any change in average wind stress curl. Through these curl reversals, the ice‐ocean stress provides a key feedback in Beaufort Gyre stabilization. This manuscript constitutes one of the first observational studies of ice‐ocean stress inclusive of geostrophic ocean currents, by making use of recently available remote sensing data.

Variability in the meteoric water, sea-ice melt, and Pacific water contributions to the central Arctic Ocean, 2000–2014

Alkire, M.B., J. Morison, and R. Andersen, "Variability in the meteoric water, sea-ice melt, and Pacific water contributions to the central Arctic Ocean, 2000–2014," J. Geophys. Res., 120, 1573-1598, doi:10.1002/2014JC010023, 2015.

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12 Mar 2015

Fourteen years (2000–2014) of bottle chemistry data collected during the North Pole Environmental Observatory were compiled to examine variations in the composition of freshwater (meteoric water, net sea-ice meltwater, and Pacific water) over mixed layer of the Central Arctic Ocean. In addition to significant spatial and interannual variability, there was a general decrease in meteoric water (MW) fractions at the majority of stations reoccupied over the duration of the program that was approximately balanced by a concomitant increase in freshwater from sea-ice melt (SIM FW) between 2000 and 2012. Inventories (0–120 m) of MW and SIM FW computed using available data between 2005 and 2012 exhibited similar variations over the study area, allowing for first-order estimates of the mean annual changes in MW (–389±194 km3 yr-1) and SIM FW (292±97 km3 yr-1) for the Central Arctic region. These mean annual changes were attributed to the diversion of Siberian river runoff to the Beaufort Gyre and the overall reduction of sea ice volume across the Arctic, respectively. In addition to this lower-frequency variability, spatial gradients and interannual variations in MW, SIM FW, and Pacific water contributions to specific locations were attributed to shifts in the Transpolar Drift that advects waters of eastern and western Arctic origin through the study area.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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