Abstract
Abstract. On the basis of model simulations, we examine what information on changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) can be extracted from associated changes in sea surface height (SSH), specifically from a broad Atlantic north–south gradient as has been suggested previously in the literature. Since a relation between AMOC and SSH changes can only be used as an AMOC diagnostic if it is valid independently of the specific forcing, we consider three different forcing types: increase of CO2 concentration, freshwater fluxes to the northern convection sites and the modification of Southern Ocean winds. We concentrate on a timescale of 100 yr. We find approximately linear and numerically similar relations between a sea-level difference within the Atlantic and the AMOC for freshwater as well as wind forcing. However, the relation is more complex in response to atmospheric CO2 increase, which precludes this sea-level difference as an AMOC diagnostic under climate change. Finally, we show qualitatively to what extent changes in SSH and AMOC strength, which are caused by simultaneous application of different forcings, correspond to the sum of the changes due to the individual forcings, a potential prerequisite for more complex SSH-based AMOC diagnostics.
Highlights
Due to the associated heat transport, the Atlantic Meridional Overturning Circulation (AMOC) plays an important role for the climate in the regions surrounding the North Atlantic (NA)
As an alternative to the attempt of identifying more or this, we present and analyze relations between the SL gradiless complex spatial patterns of sea-level change, which ent and AMOC changes based on simulations covering CO2, are related to the AMOC strength, it is worth considering freshwater and Southern Ocean Wind forcing with several a simple large scale north–south gradient of sea-level rise. different strengths each
All simulations have been performed with the Earth System Model of Intermediate Complexity CLIMBER-3α (Montoya et al, 2005) which is based on the ocean model MOM-3 (Pacanowski and Griffies, 1999) and a statistical-dynamical atmosphere (Petoukhov et al, 2000)
Summary
Due to the associated heat transport, the AMOC plays an important role for the climate in the regions surrounding the North Atlantic (NA). Hughes and Weaver (1994) and Thorpe et al (2001) have considered a fixed depth (of 3000 m) up to which density differences are integrated Changes in these resulting steric height differences (corresponding to changes in sea level if mass redistribution is neglected) have been shown to linearly scale with AMOC changes under increasing CO2 concentrations. As an alternative to the attempt of identifying more or this, we present and analyze relations between the SL gradiless complex spatial patterns of sea-level change, which ent and AMOC changes based on simulations covering CO2, are related to the AMOC strength, it is worth considering freshwater and Southern Ocean Wind forcing with several a simple large scale north–south gradient of sea-level rise.
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