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Harry Stern

Principal Mathematician

Email

harry@apl.washington.edu

Phone

206-543-7253

Biosketch

Harry Stern studies Arctic sea ice and climate using satellite data. Current interests include the changing sea ice habitat of polar bears and narwhals, and the history of Arctic exploration. He participated in the Around the Americas expedition, sailing through the eastern half of the Northwest Passage in 2009. He served as an Associate Editor for the Journal of Geophysical Research—Oceans (2007–2010). He helped to launch the annual Polar Science Weekend at Seattle's Pacific Science Center, and now runs the event. He has a B.S. in mathematics and M.S. in applied mathematics. He has been with the Polar Science Center since 1987 and with the University since 1980.

Department Affiliation

Polar Science Center

Education

B.S. Mathematics, Stanford University, 1980

M.S. Applied Mathematics, University of Washington, 1982

Videos

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.

A Look Back to Arctic Climate in the 18th Century

Captain James Cook’s logs and maps give insight to late-18th century sea ice conditions north of Bering Strait.

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15 Nov 2016

Polar Science Center mathematician Harry Stern used these records to plot the sea ice edge that Cook encountered in 1778. These earliest records of summer ice extent in the Chukchi Sea underscore the dramatic recent changes in arctic climate.

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.

Publications

2000-present and while at APL-UW

Transient benefits of climate change for a high-Arctic polar bear (Ursus maritimus) subpopulation

Laidre, K.L., S.N. Atkinson, E.V. Regehr, H.L. Stern, E.W. Born, Ø. Wiig, N.J. Lunn, M Dyck, P. Heagerty, B.R. Cohen, "Transient benefits of climate change for a high-Arctic polar bear (Ursus maritimus) subpopulation," Global Change Biol., EOR, doi:10.1111/gcb.15286, 2020.

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23 Sep 2020

Kane Basin (KB) is one of the world's most northerly polar bear (Ursus maritimus) subpopulations, where bears have historically inhabited a mix of thick multiyear and annual sea ice year‐round. Currently, KB is transitioning to a seasonally ice‐free region because of climate change. This ecological shift has been hypothesized to benefit polar bears in the near‐term due to thinner ice with increased biological production, although this has not been demonstrated empirically. We assess sea‐ice changes in KB together with changes in polar bear movements, seasonal ranges, body condition, and reproductive metrics obtained from capture–recapture (physical and genetic) and satellite telemetry studies during two study periods (1993–1997 and 2012–2016). The annual cycle of sea‐ice habitat in KB shifted from a year‐round ice platform (~50% coverage in summer) in the 1990s to nearly complete melt‐out in summer (<5% coverage) in the 2010s. The mean duration between sea‐ice retreat and advance increased from 109 to 160 days (p = .004). Between the 1990s and 2010s, adult female (AF) seasonal ranges more than doubled in spring and summer and were significantly larger in all months. Body condition scores improved for all ages and both sexes. Mean litter sizes of cubs‐of‐the‐year (C0s) and yearlings (C1s), and the number of C1s per AF, did not change between decades. The date of spring sea‐ice retreat in the previous year was positively correlated with C1 litter size, suggesting smaller litters following years with earlier sea‐ice breakup. Our study provides evidence for range expansion, improved body condition, and stable reproductive performance in the KB polar bear subpopulation. These changes, together with a likely increasing subpopulation abundance, may reflect the shift from thick, multiyear ice to thinner, seasonal ice with higher biological productivity. The duration of these benefits is unknown because, under unmitigated climate change, continued sea‐ice loss is expected to eventually have negative demographic and ecological effects on all polar bears.

Interrelated ecological impacts of climate change on an apex predator

Laidre, K.L., S. Atkinson, E.V. Regehr, H.L. Stern, E.W. Born, Ø. Wiig, N.J. Lunn, and M. Dyck, "Interrelated ecological impacts of climate change on an apex predator," Ecol. Appl., EOR, doi:10.1002/eap.2071, 2020.

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10 Jan 2020

Climate change has broad ecological implications for species that rely on sensitive habitats. For some top predators, loss of habitat is expected to lead to cascading behavioral, nutritional, and reproductive changes that ultimately accelerate population declines. In the case of the polar bear (Ursus maritimus), declining Arctic sea ice reduces access to prey and lengthens seasonal fasting periods. We used a novel combination of physical capture, biopsy darting, and visual aerial observation data to project reproductive performance for polar bears by linking sea ice loss to changes in habitat use, body condition (i.e., fatness), and cub production. Satellite telemetry data from 43 (1991–1997) and 38 (2009–2015) adult female polar bears in the Baffin Bay subpopulation showed that bears now spend an additional 30 d on land (90 d in total) in the 2000s compared to the 1990s, a change closely correlated with changes in spring sea ice breakup and fall sea ice formation. Body condition declined for all sex, age, and reproductive classes and was positively correlated with sea ice availability in the current and previous year. Furthermore, cub litter size was positively correlated with maternal condition and spring breakup date (i.e., later breakup leading to larger litters), and negatively correlated with the duration of the ice‐free period (i.e., longer ice‐free periods leading to smaller litters). Based on these relationships, we projected reproductive performance three polar bear generations into the future (approximately 35 yr). Results indicate that two‐cub litters, previously the norm, could largely disappear from Baffin Bay as sea ice loss continues. Our findings demonstrate how concurrent analysis of multiple data types collected over long periods from polar bears can provide a mechanistic understanding of the ecological implications of climate change. This information is needed for long‐term conservation planning, which includes quantitative harvest risk assessments that incorporate estimated or assumed trends in future environmental carrying capacity.

Vulnerability of arctic marine mammals to vessel traffic in the increasingly ice-free Northwest Passage and Northern Sea Route

Hauser, D.D.W., K.L. Laidre, and H.L. Stern, "Vulnerability of arctic marine mammals to vessel traffic in the increasingly ice-free Northwest Passage and Northern Sea Route," Proc. Nat. Acad. Sci. USA, 115, 7617-7622, doi:10.1073/pnas.1803543115, 2018

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2 Jul 2018

The fabled Northwest Passage and Northern Sea Route that were once the quests of early Western explorers are now increasingly sea ice–free, with routine vessel transits expected by midcentury. The potential impacts of this novel vessel traffic on endemic Arctic marine mammal (AMM) species are unknown despite their critical social and ecological roles in the ecosystem and widely recognized susceptibility to ice loss. We developed a vulnerability assessment of 80 subpopulations of seven AMM species to vessel traffic during the ice-free season. Vulnerability scores were based on the combined influence of spatially explicit exposure to the sea routes and a suite of sensitivity variables. More than half of AMM subpopulations (42/80) are exposed to open-water vessel transits in the Arctic sea routes. Narwhals (Monodon monoceros) were estimated to be most vulnerable to vessel impacts, given their high exposure and sensitivity, and polar bears (Ursus maritimus) were estimated to be the least vulnerable because of their low exposure and sensitivity. Regions with geographic bottlenecks, such as the Bering Strait and eastern Canadian Arctic, were characterized by two to three times higher vulnerability than more remote regions. These pinch points are obligatory pathways for both vessels and migratory AMMs, and so represent potentially high conflict areas but also opportunities for conservation-informed planning. Some of the species and regions identified as least vulnerable were also characterized by high uncertainty, highlighting additional data and monitoring needs. Our quantification of the heterogeneity of risk across AMM species provides a necessary first step toward developing best practices for maritime industries poised to advance into this rapidly changing seascape.

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In The News

Some polar bears in far north are getting short-term benefit from thinning ice

UW News, Hannah Hickey

A small subpopulation of polar bears lives on what used to be thick, multiyear sea ice far above the Arctic Circle. They are healthier as conditions are warming because thinning and shrinking multiyear sea ice is allowing more sunlight to reach the ocean surface, which makes the ecosystem more productive. photo: Carsten Egevang

23 Sep 2020

Polar bears are getting thinner and having fewer cubs

CNN, Scottie Andrew

The impact of the climate crisis is becoming more and more obvious to humans and their animal neighbors. But among all species, polar bears might be some of the hardest hit.

14 Feb 2020

Polar bears in Baffin Bay skinnier, having fewer cubs due to less sea ice

UW News, Hannah Hickey

Polar bears are spending more time on land than they did in the 1990s due to reduced sea ice, new University of Washington-led research shows. Bears in Baffin Bay are getting thinner and adult females are having fewer cubs than when sea ice was more available.

12 Feb 2020

More News Items

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