Somewhere along the steep fjords of Southeast Greenland, a small group of polar bears has been doing something their species was never supposed to do: hunting seals from chunks of glacial ice instead of the vast sea-ice platforms that polar bears have depended on for hundreds of thousands of years. When geneticists recently compared these bears’ DNA to that of polar bears living in more traditional ice-rich habitats, they found the differences went deeper than behavior. The bears’ genomes themselves were diverging.
That discovery is part of a growing body of peer-reviewed research showing that polar bears are not just losing habitat to a warming Arctic. In populations exposed to the most severe sea-ice declines, their DNA is measurably shifting, with changes appearing in gene regulation, gene flow patterns, and the activity of mobile genetic elements. The findings, drawn from fieldwork spanning Greenland and the Barents Sea over more than two decades, suggest the species is undergoing molecular-level change on timescales scientists can track in real time.
Genetic divergence in Greenland’s polar bears
A 2025 study published in Mobile DNA compared polar bears from Northeast Greenland, where sea ice still persists for much of the year, with bears from Southeast Greenland, where ice conditions are far more limited. The researchers found significant differences in transposable element activity between the two groups, along with divergent expression in genes connected to thermal stress.
Transposable elements, sometimes called “jumping genes,” are segments of DNA that can move to new positions within the genome and alter how nearby genes are switched on or off. Their varying activity levels between these two subpopulations correlate with differences in local climate conditions, suggesting that gene regulation may be diverging in bears living just a few hundred miles apart. The study stopped short of proving that these molecular differences improve survival, but the pattern was clear: bears in low-ice environments carry distinct genomic signatures that bears in ice-rich zones do not.
The Southeast Greenland bears had already drawn scientific attention. A 2022 study led by Kristin Laidre of the University of Washington, published in Science and funded by NASA, identified them as a previously unknown subpopulation. These bears hunt on glacial melange, a mix of freshwater ice and marine fragments calved from glaciers, rather than relying on traditional sea-ice platforms. The discovery showed that at least some bears can sustain themselves in fjord environments with minimal sea ice, a behavioral and ecological split from the broader species pattern. Local geography, including steep-sided fjords, fast-flowing glaciers, and persistent melange, appears to create microrefugia that buffer a small number of animals from regional warming trends.
Fragmenting populations in the Barents Sea
In the Barents Sea, a separate research team led by Simo Njabulo Maduna and colleagues conducted genetic sampling of polar bears across the Svalbard archipelago and surrounding waters from 1995 to 2016. Their work, published in Proceedings of the Royal Society B in 2021, found that rapid sea-ice loss was associated with declining gene flow and increasing genetic differentiation among bear groups in the region. As ice corridors that once connected populations shrank or vanished, bears became more isolated, and their gene pools began to diverge on timescales visible within a single human generation.
The researchers linked these genetic patterns directly to satellite-derived ice records, strengthening the case that habitat fragmentation, not random genetic drift alone, is driving the observed splits. The Svalbard region has experienced some of the fastest warming anywhere in the Arctic, with winter sea-ice extent declining dramatically since the late 1990s, making it a bellwether for what other polar bear populations may face.
These contemporary changes sit on top of older evolutionary adaptations. Comparative genomics research published in Cell in 2014 identified strong positive selection in polar bear lineages for the APOB gene, which plays a role in lipid metabolism and cardiovascular function, reflecting adaptation over hundreds of thousands of years to a high-fat marine mammal diet in extreme cold. Ancient DNA studies have also documented gene flow from polar bears into brown bears during past climate shifts, confirming that the polar bear genome has a long history of responding to environmental pressure. That deep evolutionary flexibility helps explain why present-day molecular shifts are biologically plausible, even if the current rate of warming is without precedent.
What scientists still cannot answer
The genetic shifts documented so far raise as many questions as they resolve. The Southeast Greenland bears that survive on glacial melange occupy a rare habitat type. Glacial melange exists in only a handful of Arctic fjord systems, and scientists have cautioned that this adaptation strategy cannot scale to most bears. The global polar bear population, estimated by the International Union for Conservation of Nature at roughly 26,000 individuals as of its most recent assessment, is spread across 19 subpopulations. Most of those subpopulations occupy open-ocean or coastal sea-ice habitats where no glacial melange alternative exists. The Southeast Greenland group, numbering only a few hundred bears, may represent a localized exception rather than a preview of the species’ future.
No published data yet connect specific transposable element variants in Greenland bears to measurable differences in survival or reproductive success. The Mobile DNA study established that TE activity differs between subpopulations in different climate zones, but whether those molecular differences translate into fitness advantages during low-ice years has not been tested. Direct measurements of offspring survival tied to particular genetic variants remain absent from the published record. Scientists can say that genomes are changing, but not yet whether those changes are helping bears keep pace with the stress they face.
The Barents Sea sampling ended in 2016. No post-2016 field data confirming whether genetic differentiation has continued, accelerated, or stabilized in Svalbard bears have been published as of June 2026. Arctic sea ice has continued to decline since then. The genetic trajectory of these populations over the past decade is an open question. A U.S. Geological Survey genetic dataset from the Chukchi Sea provides raw genotype data for ongoing monitoring, but no published analysis has yet matched those markers against recent ice-loss metrics. Until newer samples are processed and compared, researchers cannot say whether the Barents pattern is emerging elsewhere across the polar bear’s range.
Gene flow patterns across the broader Arctic also carry uncertainty. A USGS-summarized circumpolar genetics paper reported directional movement and mating patterns shifting toward regions expected to retain sea ice longer, such as the Canadian Arctic Archipelago. But whether this movement represents a durable population-level response or a temporary behavioral shift tied to specific ice years is not yet clear. Some bears may be tracking short-term foraging opportunities rather than permanently relocating their breeding ranges, and distinguishing between those scenarios requires longer time series than currently exist.
Genomes in motion, on a shrinking clock
The existing research supports a cautious but clear conclusion: polar bears are already exhibiting genetic and behavioral divergence in places where sea ice is disappearing fastest. Those changes demonstrate both the species’ capacity to respond to environmental pressure and the limits of that flexibility.
The strongest studies, peer-reviewed genomics papers with defined sampling protocols, specific geographic coordinates, and replicable methods, show genomes in motion. The Barents Sea work by Maduna et al., the Mobile DNA transposable element paper, and the Cell population genomics research all identify specific genes, allele frequencies, or regulatory changes tied to documented environmental conditions. Institutional summaries from NASA and USGS provide accessible descriptions of these findings but compress technical detail; the underlying papers contain the sampling designs, statistical tests, and caveats that determine how broadly any single claim can be applied.
Paleogenomic evidence, including research showing ancient gene flow between polar bears and brown bears, establishes that bear genomes have responded to past climate shifts through admixture and introgression. That deep evolutionary context helps frame what kinds of genetic change are plausible, but past climate transitions unfolded over thousands of years. Current sea-ice losses are occurring over decades.
What the research has not yet delivered is the critical link between specific genetic variants and actual survival outcomes. Future work connecting molecular changes to reproduction, cub survival, and movement across a rapidly shifting ice landscape will determine whether today’s adaptations represent a genuine lifeline for polar bears or simply a molecular record of a species running out of room.
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*This article was researched with the help of AI, with human editors creating the final content.
