Sack Lunch Seminar (SLS)

Under the harsh winter conditions of the north-western Atlantic Ocean, surface water in the Labrador Sea mixes with water from deeper layers to form a homogeneous water mass known as Labrador Sea Water (LSW). The amount of LSW formed displays a large interannual variability with a depth of convection ranging from only 200 m to over 2000 m depth. In order to understand the driving mechanisms behind this variability, we need to understand how the ocean and atmosphere drive and limit convective mixing in this region. I will zoom in onto two aspects that are important for convective variability: (1) the roles that three different mesoscale eddies play in the restratification season after deep convection and (2) the way in which the fresh surface layer inhibited deep convective mixing in the particular case of the 1969-1971 period. The first item is studied using the MIT gcm model in a highly idealized regional configuration of the Labrador Sea, where we found a dominant role played by one particular eddy type. The second issue was studied using in situ data taken from an ocean weather station in the central Labrador Sea. The analysis shows that the role played by fresh water in the surface is more complicated than commonly assumed, with a feedback mechanisms which actively decreases the surface heat flux as long as deep convection is inhibited.