Ocean Sci. Discuss., 8, 1403-1440, 2011
www.ocean-sci-discuss.net/8/1403/2011/
doi:10.5194/osd-8-1403-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Ocean Science (OS). Please refer to the corresponding final paper in OS.
Wind forcing of salinity anomalies in the Denmark Strait overflow
S. Hall1,2, S. R. Dye2, K. J. Heywood1, and M. R. Wadley3
1School of Environmental Sciences, University of East Anglia, Norwich, UK
2Centre for Environment, Fisheries and Aquaculture Science (Cefas), Lowestoft, UK
3School of Mathematics, University of East Anglia, Norwich, UK

Abstract. The overflow of dense water from the Nordic Seas to the North Atlantic through Denmark Strait is an important part of the global thermohaline circulation. The salinity of the overflow plume has been measured by an array of current meters across the continental slope off the coast of Angmagssalik, southeast Greenland since September 1998. During 2004 the salinity of the overflow plume changed dramatically, with the entire width of the array (70 km) freshening between January 2004 and July 2004, with a significant negative salinity anomaly of about 0.06 in May. The event in May represents a fresh anomaly of over 3 standard deviations from the mean since recording began in 1998. We show that the OCCAM 1/12° Ocean General Circulation Model not only reproduces the 2004 freshening event (r=0.96, p<0.01), but also correlates well with salinity observations over a previous 6 year period (r=0.54, p<0.01). Consequently the physical processes causing the 2004 anomaly and prior variability in salinity are investigated using the model output. Our results reject the hypotheses that the anomaly is caused by processes occurring between the overflow sill and the moorings, or by an increase in upstream net freshwater input. Instead, we show that the 2004 salinity anomaly is caused by an increase in volume flux of low salinity water, with a potential density greater than 27.60 kg m−3, flowing towards the Denmark Strait sill in the East Greenland Current. This is caused by an increase of southward wind stress upstream of the sill at around 75° N 20° W four and a half months earlier, and an associated spin-up of the Greenland Sea Gyre.

Citation: Hall, S., Dye, S. R., Heywood, K. J., and Wadley, M. R.: Wind forcing of salinity anomalies in the Denmark Strait overflow, Ocean Sci. Discuss., 8, 1403-1440, doi:10.5194/osd-8-1403-2011, 2011.
 
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