Freshwater fluxes and vertical mixing in the Labrador Sea

• Main Author: Schulze, Lena M.
• Format: Thesis
• Language: English
• Published: 2016
• Subjects: Greenland; Labrador Sea
• Online Access: https://eprints.soton.ac.uk/391105/; https://eprints.soton.ac.uk/391105/1/Schulze%252C%2520Lena_PhD_Thesis_Mar_16.pdf

The Labrador Sea plays an important role in the Meridional Overturning Circulation (MOC), due to the seasonal occurrence of deep convection in this region. Heat loss during mixing is balanced by heat import from the boundaries, while the seasonal freshening plays an important role in the restratification of the water column. Recent increases in freshwater input to high latitudes through accelerated rates of pack ice and glacial melt, has the potential to affect the convection in the Labrador Sea and therefore the global ocean circulation. It is more important than ever to understand the influence these changes have on the dynamics in the Labrador Sea. Understanding pathways of freshwater fluxes into the region of deep convection and the impact of storms on the mixing in the Labrador Sea will help to predict potential changes in the MOC. To analyse recent changes in freshwater water in the Labrador Sea, an ARGO-based heat and freshwater budget of the Labrador Sea is calculated for 2002 – 2011. Over this time period a freshening of the surface waters (0 – 100 m) is observed. Between the first and second 5-year period, observations indicate a gain of 40 cm of freshwater to the surface. The surface freshening is comparable to past freshening periods associated with a reduction of deep convection (e.g. the Great Salinity Anomaly). However, the observed surface freshening is offset by subsurface warming and enhanced salinities (100 – 2000 m), distinguishing it from the past freshening periods. To investigate pathways of freshwater fluxes a particle tracking tool is used in a NEMO 1/12o ocean model. Seasonally, two peaks of freshening are observed (in spring and fall), consistent with observations. The freshening is due to the freshwater content of the coastal water along the coast of Greenland and the rate of advection of West Greenland Water. The large year-to-year variability in advection can mainly be attributed to changes in Ekman transport. To analyse recent changes in freshwater water in the Labrador Sea, an ...