The Last Ice Area (LIA), located north of the Canadian Arctic Archipelago and Greenland, has the Arctic's oldest and thickest sea ice. The LIA is hypothesized to be a potential climate refuge for ice-dependent top predators as Arctic sea ice continues to decline. However, recent studies indicate the region may be less resilient than expected. We used a coupled biophysical model to examine the impact of changes in sea ice and nutrient availability on the LIA marine planktonic ecosystem and the ecological potential of this critical area. The model was used to generate two downscaled simulations which were forced by two Intergovernmental Panel on Climate Change AR6 climate models (GFDL-ESM4 and CNRM-CM6-1-HR using the SSP5-8.5 shared socioeconomic pathway) to investigate potential changes in primary productivity (PP) with different rates of future warming. Both downscaled model runs, which captured observed sea ice dynamics, predicted declines in LIA sea ice concentration and thickness. Under CNRM-CM6-1-HR, summer sea ice was largely absent from the LIA by 2055–2070, shortly after it disappeared elsewhere in the Arctic. Under GFDL-ESM4, some summer sea ice persisted through 2070 although concentration and thickness were low. Concurrently with declining sea ice, both models predicted increases in PP through 2070, with annual values peaking in August. While increased PP would support higher trophic levels, ice-dependent top predators require an ice platform for foraging and resting. Our approach of integrating physical and biological forecasts is a step towards a more complete picture to date of anticipated ecological changes in the LIA. We identify future research needs, which include evaluating additional climate models and forcing scenarios, collecting in situ ecological data, and obtaining a mechanistic understanding of how lower level ecological changes will affect top predators.

Evaluating the demographic status of large mammals in dynamic habitats is challenging. The east Greenland (EG) polar bear (Ursus maritimus) subpopulation ranges over approximately 1.5 million km² of sea ice and 18° of latitude along a mostly uninhabited coastline, making it the most expansive of the world's 20 polar bear subpopulations. We report on a distance-sampling aerial survey that provided the first estimate of abundance for EG polar bears. We used a density surface model (DSM) that corrected for incomplete detection on the transect line using mark-recapture methods, accounted for overall detectability via distance-sampling methods, and modeled bear density as a function of environmental covariates with a generalized additive model. Our study design was informed by Indigenous Knowledge surveys and 3 decades of polar bear movement data obtained from satellite telemetry. During March–May 2023, we flew 106.5 h on-effort over 26 survey days and sighted 84 groups of bears (108 individuals). Mean observed litter size was 1.6 (95% CI = 1.2–2.0) for cubs-of-the-year and 1.6 (95% CI = 1.3–1.8) for yearlings. Polar bear density was higher closer to land and along the continental shelf break offshore, where bathymetry deepens from 300 to 1000 m. Polar bear density was approximately 5 times lower within 50 km of subsistence hunting communities (0.06 bears 100 km^-2) compared to the rest to the study area (0.31 bears 100 km^-2). The best estimate of abundance for the EG subpopulation, adjusted for animals located outside the sampling area, was 2275 bears (CV = 0.27, 95% CI = 1360–3807). This estimate can be used to identify a sustainable level of subsistence harvest, manage human–bear conflicts, and monitor the effects of climate warming on EG polar bears. Our methods also provide a template for designing and conducting aerial surveys for wildlife populations inhabiting vast and remote regions.

Southeast Greenland (SEG) is characterized by complex morphology and environmental processes that create dynamic habitats for top marine predators. Active glaciers producing solid-ice discharge, freshwater flux, offshore sea ice transport, and seasonal landfast-ice formation all contribute to a variable, transient environment within SEG fjord systems. Here, we investigate a selection of physical processes in SEG to provide a regional characterization that reveals physical system processes and supports biological research. SEG fjords exhibit high fjord-to-fjord variability regarding bathymetry, size, shape, and glacial setting, influencing some processes more than others. For example, during fall, the timing of offshore sea ice formation near SEG fjords progresses temporally when moving southward across latitudes, while the timing of offshore sea ice disappearance is less dependent on latitude. The rates of annual freshwater flux into fjords, however, are highly variable across SEG, with annual average input values ranging from ~1 x 10⁸ to ~1.25 x 10¹⁰ m³ (~0.1–12.5 Gt) for individual fjords. Similarly, the rates of solid-ice discharge in SEG fjords vary widely — partly due to the irregular distribution of active glaciers across the study area (60–70°N). Landfast sea ice, assessed for eight focus fjords, is seasonal and has a spatial distribution highly dependent on individual fjord topography. Conversely, glacial ice is deposited into fjord systems year-round, with the spatial distribution of glacier-derived ice depending on the location of glacier termini. As climate change continues to affect SEG, the evolution of these metrics will vary individually in their response, and next steps should include moving from characterization to system projection. Due to the projected regional ice sheet persistence that will continue to feed glacial ice into fjords, it is possible that SEG could remain a long-term refugium for polar bears and other ice-dependent species on a centennial to millennial scale, demonstrating a need for continued research into the SEG physical environment.