Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea
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Fenty-2013-Hydrographic precond.pdf
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4.33 MB
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Author(s)
Fenty, Ian
Heimbach, Patrick
Date Issued
May 2013
Journal
Journal of Physical Oceanography
Publisher
American Meteorological Society
Citation
Fenty, Ian, and Patrick Heimbach. “Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea.” Journal of Physical Oceanography 43, no. 5 (May 2013): 863-883. © 2013 American Meteorological Society
Version
Final published version
Abstract
This study investigates the hydrographic processes involved in setting the maximum wintertime sea ice (SI) extent in the Labrador Sea and Baffin Bay. The analysis is based on an ocean and sea ice state estimate covering the summer-to-summer 1996/97 annual cycle. The estimate is a synthesis of in situ and satellite hydrographic and ice data with a regional coupled ⅓° ocean–sea ice model. SI advective processes are first demonstrated to be required to reproduce the observed ice extent. With advection, the marginal ice zone (MIZ) location stabilizes where ice melt balances ice mass convergence, a quasi-equilibrium condition achieved via the convergence of warm subtropical-origin subsurface waters into the mixed layer seaward of the MIZ.
An analysis of ocean surface buoyancy fluxes reveals a critical role of low-salinity upper ocean (100 m) anomalies for the advancement of SI seaward of the Arctic Water–Irminger Water Thermohaline Front. Anomalous low-salinity waters slow the rate of buoyancy loss–driven mixed layer deepening, shielding an advancing SI pack from the warm subsurface waters, and are conducive to a positive surface meltwater stabilization enhancement (MESEM) feedback driven by SI meltwater release. The low-salinity upper-ocean hydrographic conditions in which the MESEM efficiently operates are termed sea ice–preconditioned waters (SIPW).
The SI extent seaward of the Thermohaline Front is shown to closely correspond to the distribution of SIPW. The analysis of two additional state estimates (1992/93, 2003/04) suggests that interannual hydrographic variability provides a first-order explanation for SI maximum extent anomalies in the region.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1175/JPO-D-12-064.1
