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This paper explores the concept of co-stewardship in the Arctic through the lens of the Study of Environmental Arctic Change’s Human Wellbeing (HWB) team. Rooted in Indigenous knowledge and collaborative science, our work prioritizes equity in decision-making, recognizing multiple knowledge systems as equally valuable. Through intentional team-building, trust, and reciprocity, we examine successes, challenges, and opportunities in co-stewardship. Key successes include fostering meaningful relationships, integrating Indigenous perspectives into scientific and policy discussions, and uplifting innovative knowledge-sharing tools such as oral histories and visual storytelling. However, structural challenges persist, including colonial policy frameworks, inadequate funding models, and a lack of institutional mechanisms to support Indigenous leadership in co-stewardship initiatives. We propose policy shifts, long-term funding commitments, and greater Indigenous representation in decision-making as steps toward meaningful change. This work underscores the importance of Indigenous-led stewardship in addressing Arctic environmental and social challenges, offering a model for collaborative governance rooted in respect and reciprocity. 

Abstract. In the high-latitude Arctic, wintertime sea ice and snowinsulate the relatively warmer ocean from the colder atmosphere. While theclimate warms, wintertime Arctic surface heat fluxes remain dominated by theinsulating effects of snow and sea ice covering the ocean until the sea icethins enough or sea ice concentrations decrease enough to allow for directocean–atmosphere heat fluxes. The Community Earth System Model version 1 LargeEnsemble (CESM1-LE) simulates increases in wintertime conductive heat fluxesin the ice-covered Arctic Ocean by ∼ 7–11 W m−2 bythe mid-21st century, thereby driving an increased warming of theatmosphere. These increased fluxes are due to both thinning sea ice anddecreasing snow on sea ice. The simulations analyzed here use a sub-grid-scaleice thickness distribution. Surface heat flux estimates calculated usinggrid-cell mean values of sea ice thicknesses underestimate mean heat fluxesby ∼16 %–35 % and overestimate changes in conductive heatfluxes by up to ∼36 % in the wintertime Arctic basin evenwhen sea ice concentrations remain above 95 %. These results highlight howwintertime conductive heat fluxes will increase in a warming world evenduring times when sea ice concentrations remain high and that snow and thedistribution of snow significantly impact large-scale calculations ofwintertime surface heat budgets in the Arctic. 

Under rising atmospheric greenhouse gas concentrations, the Arctic exhibits amplified warming relative to the globe. This Arctic amplification is a defining feature of global warming. However, the Arctic is also home to large internal variability, which can make the detection of a forced climate response difficult. Here we use results from seven model large ensembles, which have different rates of Arctic warming and sea ice loss, to assess the time of emergence of anthropogenically-forced Arctic amplification. We find that this time of emergence occurs at the turn of the century in all models, ranging across the models by a decade from 1994–2005. We also assess transient changes in this amplified signal across the 21st century and beyond. Over the 21st century, the projections indicate that the maximum Arctic warming will transition from fall to winter due to sea ice reductions that extend further into the fall. Additionally, the magnitude of the annual amplification signal declines over the 21st century associated in part with a weakening albedo feedback strength. In a simulation that extends to the 23rd century, we find that as sea ice cover is completely lost, there is little further reduction in the surface albedo and Arctic amplification saturates at a level that is reduced from its 21st century value. 

Abstract. We assess the influence of snow on sea ice in experimentsusing the Community Earth System Model version 2 for a preindustrial and a2xCO2 climate state. In the preindustrial climate, we find that increasingsimulated snow accumulation on sea ice results in thicker sea ice and acooler climate in both hemispheres. The sea ice mass budget response differsfundamentally between the two hemispheres. In the Arctic, increasing snowresults in a decrease in both congelation sea ice growth and surface sea icemelt due to the snow's impact on conductive heat transfer and albedo,respectively. These factors dominate in regions of perennial ice but have asmaller influence in seasonal ice areas. Overall, the mass budget changeslead to a reduced amplitude in the annual cycle of ice thickness. In theAntarctic, with increasing snow, ice growth increases due to snow–iceformation and is balanced by larger basal ice melt, which primarily occursin regions of seasonal ice. In a warmer 2xCO2 climate, the Arctic sea icesensitivity to snow depth is small and reduced relative to that of thepreindustrial climate. In contrast, in the Antarctic, the sensitivity tosnow on sea ice in the 2xCO2 climate is qualitatively similar to thesensitivity in the preindustrial climate. These results underscore theimportance of accurately representing snow accumulation on sea ice incoupled Earth system models due to its impact on a number of competingprocesses and feedbacks that affect the melt and growth of sea ice. 

Abstract The Arctic is undergoing a pronounced and rapid transformation in response to changing greenhouse gasses, including reduction in sea ice extent and thickness. There are also projected increases in near‐surface Arctic wind. This study addresses how the winds trends may be driven by changing surface roughness and/or stability in different Arctic regions and seasons, something that has not yet been thoroughly investigated. We analyze 50 experiments from the Community Earth System Model Version 2 (CESM2) Large Ensemble and five experiments using CESM2 with an artificially decreased sea ice roughness to match that of the open ocean. We find that with a smoother surface there are higher mean wind speeds and slower mean ice speeds in the autumn, winter, and spring. The artificially reduced surface roughness also strongly impacts the wind speed trends in autumn and winter, and we find that atmospheric stability changes are also important contributors to driving wind trends in both experiments. In contrast to the clear impacts on winds, the sea ice mean state and trends are statistically indistinguishable, suggesting that near‐surface winds are not major drivers of Arctic sea ice loss. Two major results of this work are: (a) the near‐surface wind trends are driven by changes in both surface roughness and near‐surface atmospheric stability that are themselves changing from sea ice loss, and (b) the sea ice mean state and trends are driven by the overall warming trend due to increasing greenhouse gas emissions and not significantly impacted by coupled feedbacks with the surface winds. 

We assess Antarctic sea ice climatology and variability in version 2 of the Community Earth System Model (CESM2), and compare it to that in the older CESM1 and (where appropriate) real-world observations. In CESM2, Antarctic sea ice is thinner and less extensive than in CESM1, though sea ice area is still approximately 1 million km2 greater in CESM2 than in present-day observations. Though there is less Antarctic sea ice in CESM2, the annual cycle of ice growth and melt is more vigorous in CESM2 than in CESM1. A new mushy-layer thermodynamics formulation implemented in the latest version of the Community Ice Code (CICE) in CESM2 accounts for both greater frazil ice forma- tion in coastal polynyas and more snow-to-ice conversion near the edge of the ice pack in the new model. Greater winter ice divergence in CESM2 (relative to CESM1) is due to stronger stationary wave activity and greater wind stress curl over the ice pack. Greater wind stress curl, in turn, drives more warm water upwelling under the ice pack, thinning it and decreasing its extent. Overall, differences between Antarctic sea ice in CESM2 and CESM1 arise due to both differences in their sea ice thermodynamics formulations, and differences in their coupled atmosphere-ocean states.