The Response of Ocean Salinity Patterns to Climate Change: Implications for Circulation

Samuel Levang, Ph.D., 2019
Raymond Schmitt, Advisor

In a warming climate, the atmosphere holds additional water vapor which acts to intensify the global water cycle. This forces changes in salinity at the ocean surface, which then propagate along circulation pathways. Here, we use coupled model results from the CMIP5 experiment to identify coherent responses in the atmospheric water cycle and in ocean salinity patterns. To understand how differences in ocean circulation may affect this response, we use two techniques. The first is a salt budget within the surface mixed layer, which identifies major transport processes. The second is a Lagrangian particle tracking tool, used to understand the regional connectivity of water masses. We find that anomalous freshwater signals become well mixed within the ocean gyres, but can be isolated on larger scales. The subpolar Atlantic salinity response generally shows freshening at the surface, but is sensitive to the transport of anomalously salty water from the subtropics, a largely eddy-driven process. These surface changes ultimately propagate into deeper layers with a complex dependence on advective pathways. In a warming scenario, water cycle amplification actually works to strengthen the Atlantic meridional overturning circulation due to the influence of enhanced subtropical evaporation.