The variability of the Denmark Straight overflow

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. Therefore changes to the properties of Denmark Strait Overflow Water (DSOW) may have the potential to influence the global climate. This thesis has used observations from current meters, output from an eddy resolving Ocean General Circulation Model and oxygen isotope ratio data to investigate the mechanisms responsible for variability of DSOW salinity. Three main conclusions have been drawn: • DSOW salinity anomalies are probably caused by changes in the proportions of source waters feeding the overflow, rather than changes in the salinity of the source waters. This is caused by an increase in southward wind stress off the East Greenland coast and a subsequent increase in volume flux of fresh intermediate water arriving at the sill. This results in a freshening of DSOW, with a lag of 4 'li months from the wind stress change. • Eddy variability at the moorings may be linked to different proportions of source waters feeding the overflow at the sill, and therefore may be indirectly linked to the wind forcing off the East Greenland coast. This means that short term variability in salinity of a few days at the moorings, could be driven by processes occurring upstream of the sill on much longer interannual time scales. • DSOW freshwater input derives from meteoric water (i.e. no sea-ice melt input) for the period of June 2009, and a proportion of DSOW source water has also formed sea- ice upstream of the sill. Oxygen isotope ratio analysis is a useful tool to provide an insight into the nature of the regions where DSOW source waters may last have been in contact with the surface.EThOS - Electronic Theses Online ServiceGBUnited Kingdo