The Atlantic Water Boundary Current in the Chukchi Borderland and Southern Canada Basin. Issue 8 (14th August 2020)

• Record Type: Journal Article
• Authors: Li, Jianqiang; Pickart, Robert S.; Lin, Peigen; Bahr, Frank; Arrigo, Kevin R.; Juranek, Laurie; Yang, Xiao‐Yi
• Is Part Of: Journal of geophysical research. Volume 125:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-14
• Subjects: Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2020JC016197
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Synoptic shipboard measurements, together with historical hydrographic data and satellite data, are used to elucidate the detailed structure of the Atlantic Water (AW) boundary current system in the southern Canada Basin and its connection to the upstream source of AW in the Chukchi Borderland. Nine high‐resolution occupations of a transect extending from the Beaufort shelf to the deep basin near 152°W, taken between 2003 and 2018, reveal that there are two branches of the AW boundary current that flow beneath and counter to the Beaufort Gyre. Each branch corresponds to a warm temperature core and transports comparable amounts of Fram Strait Branch Water between roughly 200–700 m depth, although they are characterized by a different temperature/salinity ( T / S ) structure. The mean volume flux of the combined branches is 0.87 ± 0.13 Sv. Using the historical hydrographic data, the two branches are tracked upstream by their temperature cores and T/S signatures. This sheds new light on how the AW negotiates the Chukchi Borderland and why two branches emerge from this region. Lastly, the propagation of warm temperature anomalies through the region is quantified and shown to be consistent with the deduced circulation scheme. Plain Language Summary: Warm water flows into the Arctic Ocean from the North Atlantic and circulates counterclockwise through the different subbasins of the Arctic. The water is cooled, freshened, and densified as part of the global overturning circulation. The warm water also spreads into the interior Arctic with the potential to melt sea ice. Presently, very little is known about the Atlantic Water (AW) circulation in the Canada Basin, far from the source of the water. In this study, we analyze nine repeat shipboard transects extending from the Beaufort Sea shelf to the deep basin, taken between 2003 and 2018. The transects reveal that there are two branches of the AW boundary current, each characterized by a warm temperature core. The branches transport roughly equal amounts of water. Using an extensive historical database, we demonstrate that the two branches emerge from a region of complex topography known as the Chukchi Borderland. A single AW current entering the Borderland undergoes a series of divisions and merges, which ultimately forms two branches that are further distinguishable by their temperature and salinity structure. Finally, we document the propagation of warm temperature pulses through the region, which is consistent with the deduced circulation scheme. Key Points: The Atlantic Water boundary current has two branches in the southern Canada Basin, flowing beneath and counter to the Beaufort Gyre The two branches emerge from the Chukchi Borderland due to a series of bifurcations of the single branch that enters the Borderland The propagation of warm temperature anomalies through the region is consistent with the deduced circulation scheme