From small whirls to the global ocean

/ March 23, 2015/ IMAU, Ocean Circulation and Climate

In May 2014, Caroline Katsman received a VIDI grant from the Netherlands Organization for Scientific Research (NWO) to investigate how ocean eddies govern the response of the Atlantic Meridional Overturning Circulation (AMOC) to high-latitude climate change.

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Physical oceanographer and Vidi laureate Caroline Katsman researches sinking seawater Credits: Fjodor Buis

In the marginal seas of the North Atlantic Ocean (Labrador Sea, Irminger Sea, and Greenland-Iceland-Norwegian Seas), surface waters are cooled by the atmosphere, mix vertically with waters below, sink, and return southward at depth. This three-dimensional AMOC transports vast amounts of heat northward and is very important for the Earth’s climate. Climate models project a significant weakening of the AMOC by the year 2100, with a regional -additional- sea level rise of several tens of centimetres along the Dutch coast as one of the consequences. However, these climate models lack a crucial feature: the small-scale eddies that are abundant in the ocean and -as was recently revealed in idealized studies- dictate the sinking and spreading of convectively-formed dense waters.

In Katsman’s proposed research, for the first time all spatial scales involved will be covered: from the interplay between these small-scale eddies, vertical mixing and sinking in a single marginal sea to the global-scale overturning circulation. This is achieved by combining regional high-resolution process studies with the analysis of global-scale simulations at eddy-resolving resolution and (climate model-like) non eddy- resolving resolution. The latter will be made available by IMAU’s Henk Dijkstra and his colleagues. Two PhDs and 2 postdocs will perform the planned research in the coming five years.

In the original VIDI proposal, IMAU was listed as the host institute for this project. However, two days before the project was awarded Caroline was offered a position at Delft University of Technology as Associate Professor within the Environmental Fluid Mechanics section of the Faculty of Civil Engineering, and she decided to move. As the planned cooperation with IMAU’s ocean group is greatly appreciated, Caroline now is an official IMAU guest where she will work one day every two weeks, returning to the place where she obtained her MSc and PhD degrees before she started working at the Woods Hole Oceanographic Institution (USA) and KNMI.

You can find more information about this project here.