A wind-driven, hybrid latent and sensible heat coastal polynya off Barrow, Alaska

The nature of the Barrow Coastal Polynya (BCP), which forms episodically off the Alaska coast in winter, is examined using mooring data, atmospheric reanalysis data, and satellite-derived sea-ice concentration and production data. We focus on oceanographic conditions such as water mass distribution...

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Bibliographic Details
Published in:Journal of Geophysical Research: Oceans
Main Authors: Hirano, D, Fukamachi, Y, Watanabe, E, Ohshima, KI, Iwamoto, K, Mahoney, AR, Eicken, H, Simizu, D, Tamura, T
Format: Article in Journal/Newspaper
Language:English
Published: Wiley-Blackwell Publishing, Inc. 2016
Subjects:
Earth Sciences
Oceanography
Physical Oceanography
Arctic
Chukchi Sea
Barrow Canyon
Barrow
Chukchi
Sea ice
Alaska
Online Access:https://doi.org/10.1002/2015JC011318
http://ecite.utas.edu.au/114488
Description
Summary:The nature of the Barrow Coastal Polynya (BCP), which forms episodically off the Alaska coast in winter, is examined using mooring data, atmospheric reanalysis data, and satellite-derived sea-ice concentration and production data. We focus on oceanographic conditions such as water mass distribution and ocean current structure beneath the BCP. Two moorings were deployed off Barrow, Alaska in the northeastern Chukchi Sea from August 2009 to July 2010. For sea-ice season from December to May, a characteristic sequence of five events associated with the BCP has been identified; (1) dominant northeasterly wind parallel to the Barrow Canyon, with an offshore component off Barrow, (2) high sea-ice production, (3) upwelling of warm and saline Atlantic Water beneath the BCP, (4) strong up-canyon shear flow associated with displaced density surfaces due to the upwelling, and (5) sudden suppression of ice growth. A baroclinic current structure, established after the upwelling, caused enhanced vertical shear and corresponding vertical mixing. The mixing event and open water formation occurred simultaneously, once sea-ice production had stopped. Thus, mixing events accompanied by ocean heat flux from the upwelled warm water into the surface layer played an important role in formation/maintenance of the open water area (i.e., sensible heat polynya). The transition from a latent to a sensible heat polynya is well reproduced by a high-resolution pan-Arctic ice-ocean model. We propose that the BCP, previously considered to be a latent heat polynya, is a wind-driven hybrid latent and sensible heat polynya, with both features caused by the same northeasterly wind.

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