Arctic sea ice is a key indicator of the state of global climate because of both its sensitivity to warming and its role in amplifying climate change. Accelerated melting of the perennial sea ice cover has occurred since the late 1990s, which is important to the pan-Arctic region, through effects on atmospheric and oceanic circulations, the Greenland ice sheet, snow cover, permafrost, and vegetation. Such changes could have significant ramifications for global sea level, the ocean thermohaline circulation, native coastal communities, and commercial activities, as well as effects on the global surface energy and moisture budgets, atmospheric and oceanic circulations, and geosphere-biosphere feedbacks. However, a system-level understanding of critical Arctic processes and feedbacks is still lacking. To better understand the past and present states and estimate future trajectories of Arctic sea ice and climate, we argue that it is critical to advance hierarchical regional climate modeling and coordinate it with the design of an integrated Arctic observing system to constrain models.
Wind‐driven changes in the path of warm Bering/Chukchi waters carried by the Alaska Coastal Current (ACC) through Barrow Canyon during late summer are described from high‐resolution hydrography, acoustic Doppler current profiler–measured currents, and satellite‐measured sea surface temperature imagery acquired from mid‐August to mid‐September 2005–2007 near Barrow, Alaska. Numerical simulations are used to provide a multidecadal context for these observational data. Four generalized wind regimes and associated circulation states are identified. When winds are from the east or east‐southeast, the ACC jet tends to be relatively strong and flows adjacent to the shelf break along the southern flank of Barrow Canyon. These easterly winds drive inner shelf currents northwestward along the Alaskan Beaufort coast where they oppose significant eastward intrusions of warm water from Barrow Canyon onto the shelf. Because these easterly winds promote sea level set down over the Beaufort shelf and upwelling along the Beaufort slope, the ACC jet necessarily becomes weaker, broader, and displaced seaward from the Beaufort shelf break upon exiting Barrow Canyon. Winds from the northeast promote separation of the ACC from the southern flank of Barrow Canyon and establish an up‐canyon current along the southern flank that is fed in part by waters from the western Beaufort shelf. When winds are weak or from the southwest, warm Bering/Chukchi waters from Barrow Canyon intrude onto the western Beaufort shelf.
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