Mechanisms behind the temporary shutdown of deep convection in the Labrador Sea : lessons from the Great Salinity Anomaly years 1968–71


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dc.contributor.author Gelderloos, Renske
dc.contributor.author Straneo, Fiamma
dc.contributor.author Katsman, Caroline A.
dc.date.accessioned 2012-11-14T17:14:20Z
dc.date.available 2013-04-01T08:46:56Z
dc.date.issued 2012-10-01
dc.identifier.citation Journal of Climate 25 (2012): 6743–6755 en_US
dc.identifier.uri http://hdl.handle.net/1912/5546
dc.description Author Posting. © American Meteorological Society, 2012. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 25 (2012): 6743–6755, doi:10.1175/JCLI-D-11-00549.1. en_US
dc.description.abstract From 1969 to 1971 convection in the Labrador Sea shut down, thus interrupting the formation of the intermediate/dense water masses. The shutdown has been attributed to the surface freshening induced by the Great Salinity Anomaly (GSA), a freshwater anomaly in the subpolar North Atlantic. The abrupt resumption of convection in 1972, in contrast, is attributed to the extreme atmospheric forcing of that winter. Here oceanic and atmospheric data collected in the Labrador Sea at Ocean Weather Station Bravo and a one-dimensional mixed layer model are used to examine the causes of the shutdown and resumption of convection in detail. These results highlight the tight coupling of the ocean and atmosphere in convection regions and the need to resolve both components to correctly represent convective processes in the ocean. They are also relevant to present-day conditions given the increased ice melt in the Arctic Ocean and from the Greenland Ice Sheet. The analysis herein shows that the shutdown was initiated by the GSA-induced freshening as well as the mild 1968/69 winter. After the shutdown had begun, however, the continuing lateral freshwater flux as well as two positive feedbacks [both associated with the sea surface temperature (SST) decrease due to lack of convective mixing with warmer subsurface water] further inhibited convection. First, the SST decrease reduced the heat flux to the atmosphere by reducing the air–sea temperature gradient. Second, it further reduced the surface buoyancy loss by reducing the thermal expansion coefficient of the surface water. In 1972 convection resumed because of both the extreme atmospheric forcing and advection of saltier waters into the convection region. en_US
dc.description.sponsorship This research was funded by a grant from the NWO/SRON User Support Programme Space Research. FS acknowledges support from OCE- 0850416 and NOAA NA08OAR4310569. en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher American Meteorological Society en_US
dc.relation.uri http://dx.doi.org/10.1175/JCLI-D-11-00549.1
dc.subject Atmosphere-ocean interaction en_US
dc.subject Intermediate waters en_US
dc.subject Oceanic variability en_US
dc.title Mechanisms behind the temporary shutdown of deep convection in the Labrador Sea : lessons from the Great Salinity Anomaly years 1968–71 en_US
dc.type Article en_US
dc.description.embargo 2013-04-01 en_US
dc.identifier.doi 10.1175/JCLI-D-11-00549.1

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