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Harry Stern

Principal Mathematician






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


B.S. Mathematics, Stanford University, 1980

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


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.


2000-present and while at APL-UW

A demographic survey of the Davis Strait polar bear subpopulation using physical and genetic capture-recapture-recovery sampling

Dunham, K.D., M.G. Dyck, J.V. Ware, A.E. Derocher, E.V. Regehr, H.L. Stern, G.B. Stenson, and D.N. Koons, "A demographic survey of the Davis Strait polar bear subpopulation using physical and genetic capture-recapture-recovery sampling," Mar. Mam. Sci., EOR, doi:10.1111/mms.13107, 2024.

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14 Feb 2024

Conducting assessments to understand the effects of changing environmental conditions on polar bear (Ursus maritimus) demography has become increasingly important to inform management and conservation. Here, we combined physical (2005–2007) and genetic (2017–2018) mark-recapture with harvest recovery data (2005–2018) to estimate demographic rates of the Davis Strait polar bear subpopulation and examine the possible effects of climate, dynamic ice habitat, and prey resources on survival. Large sample sizes (e.g., 2,513 marked animals) allowed us to estimate temporal variation in annual survival rates using multistate mark-recapture-recovery models. We did not detect statistically significant effects of climate, ice habitat, and prey during the 13-year study. Estimated total abundance in 2006 was 2,190, credible interval (CRI) [1,954, 2,454] and 1,944, CRI [1,593, 2,366] in 2018. Geometric mean population growth rate (0.99, 95% CRI [0.97, 1.01]) indicated the subpopulation may have declined slightly between 2006 and 2018. However, we did not detect a declining trend in survival or substantial change in reproductive metrics over this period. Given forecasts of major environmental change we emphasize the need to review monitoring programs for this subpopulation.

Demographic response of a high-Arctic polar bear (Ursus martitimus) subpopulation to changes in sea ice and subsistence harvest

Laidre, K.L., T.W. Arnold, E.V. Regehr, S.N. Atkinson, E.W. Born, O. Wiig, N.J. Lunn, M. Dyck, H.L. Stern, S. Stapleton, B. Cohen, and D. Paetkau, "Demographic response of a high-Arctic polar bear (Ursus martitimus) subpopulation to changes in sea ice and subsistence harvest," Endanger. Species Res., 51, 73-81, doi:10.3354/esr01239, 2023.

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25 May 2023

Climate change is a long-term threat to polar bears. However, sea-ice loss is hypothesized to provide transient benefits in high latitudes, where thick multiyear ice historically limited biological productivity and seal abundance. We used joint live-recapture and dead-recovery mark-recapture models to analyze data for one of the most northerly polar bear subpopulations, Kane Basin. The data consisted of 277 initial live captures and genetic identifications (1992–1997 = 150, 2012–-2014 = 127), 89 recaptures or re-identifications (1992–1997 = 53, 2012–2014 = 36), and 24 harvest returns of research-marked bears during 1992–2014. We estimated mean annual abundance of 357 bears (95% CI: 221–493) for 2013–2014. This suggests a likely increase relative to our estimate of 224 (95% CI: 145–303) bears in the mid-1990s and relative to a previously published estimate of 164 (95% CI: 94–234) bears in the mid-1990s that used some of the same data. This is also supported by an apparent increase in the density of bears in eastern Kane Basin during 2012–2014. Estimates of total survival for females ≥3 yr old (mean ± SE: 0.95 ± 0.04) and their dependent offspring were similar to previous estimates from the 1990s, and estimates of unharvested survival for females ≥3 yr (0.96 ± 0.04) appear sufficient for positive population growth. Estimates of total survival were lower for males ≥3 yr (0.87 ± 0.06). We documented a reduction in mortality associated with subsistence harvest, likely attributable to implementation of a harvest quota by Greenland in 2006. Our findings, together with evidence for increased range sizes, improved body condition for all sex and age classes, and stable reproductive metrics, show that this small high-Arctic polar bear subpopulation remains productive and healthy. These benefits are likely temporary given predictions for continued climate change.

Glacial ice supports a distinct and undocumented polar bear subpopulation persisting in late 21st-century sea-ice conditions

Laidre, K.L. and 18 others including E.V. Regehr, B. Cohen, and H.L. Stern, "Glacial ice supports a distinct and undocumented polar bear subpopulation persisting in late 21st-century sea-ice conditions," Science, 376, 1333-1338, doi:10.1126/science.abk2793, 2022.

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17 Jun 2022

Polar bears are susceptible to climate warming because of their dependence on sea ice, which is declining rapidly. We present the first evidence for a genetically distinct and functionally isolated group of polar bears in Southeast Greenland. These bears occupy sea-ice conditions resembling those projected for the High Arctic in the late 21st century, with an annual ice-free period that is >100 days longer than the estimated fasting threshold for the species. Whereas polar bears in most of the Arctic depend on annual sea ice to catch seals, Southeast Greenland bears have a year-round hunting platform in the form of freshwater glacial mélange. This suggests that marine-terminating glaciers, although of limited availability, may serve as previously unrecognized climate refugia. Conservation of Southeast Greenland polar bears, which meet criteria for recognition as the world’s 20th polar bear subpopulation, is necessary to preserve the genetic diversity and evolutionary potential of the species.

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In The News

Polar bears of the past survived warm periods. What does that mean for the future?

Anchorage Daily News, Ned Rozell

A small population of polar bears living off Greenland and Arctic Canada increased by 1.6 times when comparing numbers from the 1990s to 2013 and 2014. Lighter sea ice might have benefited the animals because sunshine penetrates thinner ice better, which stimulates small living things. That means more food for seals, the main food of polar bears.

3 Jun 2023

Arctic ice has seen an 'irreversible' thinning since 2007, study says

Washington Post, Scott Dance

New research suggests the decline was a fundamental change unlikely to be reversed this century — perhaps proof that the planet has passed an alarming climactic tipping point. Mathematician Harry Stern offers a counterpoint.

15 Mar 2023

'Wholly unexpected': These polar bears can survive with less sea ice

The New York Times, Henry Fountain

The overall threat to the animals from climate change remains, but a new finding suggests that small numbers might survive for longer as the Arctic warms. See related articles on the UW News pinboard.

16 Jun 2022

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