Abstract
AbstractWe address the role of freshwater forcing in the modern day ocean. Specifically, we ask the question of whether an amplification of the global freshwater forcing pattern leads to a strengthening or weakening of the steady‐state Atlantic Meridional Overturning Circulation (AMOC). While the role of freshwater forcing in the AMOC has received much attention, this question remains unresolved, in part because past studies have primarily investigated idealized models, large regime shifts away from the modern ocean state, or coupled atmosphere–ocean simulations on shorter timescales than required for the deep ocean to equilibrate. Here we study the AMOC's sensitivity at equilibrium to small perturbations in the magnitude of the global freshwater fluxes in simulations performed with a realistically configured ocean circulation model. Our results robustly suggest that for the equilibrium state of the modern ocean, freshwater fluxes strengthen the AMOC, in the sense that an amplification of the existing freshwater flux‐forcing pattern leads to a strengthening of the AMOC and vice versa. A simple physical argument explains these results: the North Atlantic is anomalously salty at depth and increased freshwater fluxes act to amplify that salinity pattern, resulting in enhanced AMOC transport.
Highlights
We address the role of freshwater forcing in the modern day ocean
As the model reproduces the main features of the modern ocean’s salinity distribution and circulation for multiple types of boundary conditions, and the qualitative response is robust and explicable by a simple physical argument, the model is a compelling tool to illustrate the qualitative influence of atmospheric freshwater fluxes on the modern overturning
In Stommel’s two box model, the sign of the salt advection feedback is directly related to the sign of the atmospheric freshwater forcing: A freshwater forcing that acts to increase the salinity of the northern sinking region would automatically be associated with northward advection of freshwater by the Atlantic Meridional Overturning Circulation (AMOC) and a negative salt advection feedback
Summary
We address the role of freshwater forcing in the modern day ocean. We ask the question of whether an amplification of the global freshwater forcing pattern leads to a strengthening or weakening of the steadystate Atlantic Meridional Overturning Circulation (AMOC). While the role of freshwater forcing in the AMOC has received much attention, this question remains unresolved, in part because past studies have primarily investigated idealized models, large regime shifts away from the modern ocean state, or coupled atmosphere– ocean simulations on shorter timescales than required for the deep ocean to equilibrate. We study the AMOC’s sensitivity at equilibrium to small perturbations in the magnitude of the global freshwater fluxes in simulations performed with a realistically configured ocean circulation model. A simple physical argument explains these results: the North Atlantic is anomalously salty at depth and increased freshwater fluxes act to amplify that salinity pattern, resulting in enhanced AMOC transport
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
