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  1. Abstract

    Ocean‐to‐ice heat flux (OHF) is important in regulating the variability of sea ice mass balance. Using surface drifting buoy observations, we show that during winter in the Arctic Ocean's Beaufort Gyre region, OHF increased from 0.76 ± 0.05 W/m2over 2006–2012 to 1.63 ± 0.08 W/m2over 2013–2018. We find that this is a result of thinner and less‐compact sea ice that promotes enhanced winter ice growth, stronger ocean vertical convection, and subsurface heat entrainment. In contrast, Ekman upwelling declined over the study period, suggesting it had a secondary contribution to OHF changes. The enhanced ice growth creates a cooler, saltier, and deeper ocean surface mixed layer. In addition, the enhanced vertical temperature gradient near the mixed layer base in later years favors stronger entrainment of subsurface heat. OHF and its increase during 2006–2018 were not geographically uniform, with hot spots found in an upwelling region where ice was most seasonally variable.

     
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  2. Abstract

    The Arctic Ocean’s Wandel Sea is the easternmost sector of the Last Ice Area, where thick, old sea ice is expected to endure longer than elsewhere. Nevertheless, in August 2020 the area experienced record-low sea ice concentration. Here we use satellite data and sea ice model experiments to determine what caused this record sea ice minimum. In our simulations there was a multi-year sea-ice thinning trend due to climate change. Natural climate variability expressed as wind-forced ice advection and subsequent melt added to this trend. In spring 2020, the Wandel Sea had a mixture of both thin and—unusual for recent years—thick ice, but this thick ice was not sufficiently widespread to prevent the summer sea ice concentration minimum. With continued thinning, more frequent low summer sea ice events are expected. We suggest that the Last Ice Area, an important refuge for ice-dependent species, is less resilient to warming than previously thought.

     
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  3. Arctic storm surge events have a distinct character, and their impact on the coast is unique compared to a non-Arctic event. On the one hand, Arctic peak wind speeds rarely reach hurricane strength (74 mph, 64 knots or greater). And pressure drops associated with Arctic storms are small compared to ones in the tropics. More importantly, the impact of an atmospheric storm on the ocean and on the coast is entirely dependent on the season. If a large storm strikes during the winter or when the ocean is ice-covered, the storm will generate negligible waves and surge, and it will not generate erosion or coastal flooding. On the other hand, if a large storm strikes when the ocean is partially ice-covered (e.g., 50% covered), surge may be enhanced relative to an ice-free ocean, potentially leading to greater coastal flooding. 
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  4. Abstract Predictability of seasonal sea ice advance in the Chukchi Sea has been investigated in the context of ocean heat transport from the Bering Strait; however, the underlying physical processes have yet to be fully clarified. Using the Pan-Arctic Ice–Ocean Modeling and Assimilation System (PIOMAS) reanalysis product (1979–2016), we examined seasonal predictability of sea ice advance in early winter (November–December) and its source using canonical correlation analysis. It was found that 2-month leading (September–October) surface heat flux and ocean heat advection is the major predictor for interannual variability of sea ice advance. Surface heat flux is related to the atmospheric cooling process, which has influenced sea ice area in the southeastern Chukchi Sea particularly in the 1980s and 1990s. Anomalous surface heat flux is induced by strong northeasterly winds related to the east Pacific/North Pacific teleconnection pattern. Ocean heat advection, which is related to fluctuation of volume transport in the Bering Strait, leads to decrease in the sea ice area in the northwestern Chukchi Sea. Diagnostic analysis revealed that interannual variability of the Bering Strait volume transport is governed by arrested topographic waves (ATWs) forced by southeasterly wind stress along the shelf of the East Siberian Sea. The contribution of ocean heat flux to sea ice advance has increased since the 2000s; therefore, it is suggested that the major factor influencing interannual variability of sea ice advance in early winter has shifted from atmospheric cooling to ocean heat advection processes. Significance Statement Predictability of sea ice advance in the marginal Arctic seas in early winter is a crucial issue regarding future projections of the midlatitude winter climate and marine ecosystem. This study examined seasonal predictability of sea ice advance in the Chukchi Sea in early winter using a statistical technique and historical model simulation data. We identified that atmospheric cooling and ocean heat transport are the two main predictors of sea ice advance, and that the impact of the latter has become amplified since the 2000s. Our new finding suggests that the precise information on wind-driven ocean currents and temperatures is crucial for the skillful prediction of interannual variability of sea ice advance under present and future climatic regimes. 
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  5. Rising waters and land subsidence are increasing relative sea levels in western and northern Alaska, forcing communities to relocate or armor in place. To appropriately plan and make equitable decisions, there is a need to forecast the risk of flood exposure in coastal Alaskan communities and to evaluate methods to mitigate that risk. This paper conducts use-inspired science to evaluate the current and future flood exposure of roads in Hooper Bay, Alaska, proposes a unit cost of flood exposure to estimate the cost of flooding, and compares various mitigation efforts including elevating roads and building dikes. Nine historic storms and their associated flood depths were subject to return-period analysis and modeled for several sea level rise scenarios. Based on the simulated road flood exposure (km hours/storm), and the storm-return period, an annual flood exposure (km hours/year) was computed. Then, the unit cost of flood exposure (USD/km hours) was determined as the ratio of the cost of flood mitigation (USD/year) to the annual flood exposure mitigated by the project. The analysis found that the unit cost of flood exposure, in conjunction with flood exposure calculations, does provide an approximate flood risk calculation, though a unitized cost of flood exposure needs to be divided into lump sum costs and materials costs. The analysis also found that dikes may be a more cost-effective alternative than road elevation. The flood risk calculation, based on the unit cost of flood exposure, could be made for all of the communities in a given region to identify those communities that face a high flood risk. Furthermore, if one divides the unit cost of flood exposure by the population, one obtains a cost/benefit ratio that potentially could be used to prioritize flood mitigation work. 
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  6. This paper explores the knowledge, attitudes, and behaviors about emerging hazards, environmental change, and relocation among community groups in Utqiaġvik (Barrow) of the North Slope Borough (NSB), Alaska. This region has been experiencing accelerating erosion and warmer temperatures, permafrost thawing, more frequent and intense storm surges, and increased maritime traffic and extractive industries with ice loss, with direct or cascading effects on the mixed ethnic and indigenous communities. This paper used engagement activities (Participatory Applied Theater) and qualitative approaches (focus groups) during three consecutive summers 2016–2018 to evaluate the risk perceptions and interpretations towards coastal changes and relocation as an adaptive response in this U.S. strategic yet remote location. Each focus group session started with risk ranking activities about regional hazards to assess knowledge and perceptions of risk, followed by an interactive script reading of an Iñupiat disaster legend to facilitate discussion about risk reduction options and engagement with the survey questions. Focus groups were audio recorded, transcribed, and analyzed using qualitative data analysis software Nvivo and a hybrid coding strategy. Results indicate that relocation is considered by some participants but is not planned for nor implemented by community groups, families, or the local government to reduce the hazard risks. However, widespread recognition of accelerated hazards and environmental changes, and the need for adaptation could lead to consideration of relocation in the future. This study provides a case of disaster risk reduction in a remote place with unique place-specific characteristics (e.g., particular forms of subsistence, corporate monopolies, Traditional Ecological Knowledge, and social organizations), but also shaped by significant external influences, accompanied by a changing landscape of risk from the slow and rapid onset of environmental changes. 
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