Unraveling the mechanisms and implications of a stronger mid-Pliocene Atlantic Meridional Overturning Circulation (AMOC) in PlioMIP2

Abstract. The mid-Pliocene warm period (3.264–3.025 Ma) is the most recent geological in which atmospheric CO2 concentration was approximately equal to we measure today (ca. 400 ppm). Sea surface temperature (SST) proxies indicate above-average warming over North Atlantic with respect pre-industrial period, may be linked an intensified Meridional Overturning Circulation (AMOC). Earlier results from Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) show that ensemble simulates a stronger AMOC than pre-industrial. However, no consistent relationship between and either northward ocean heat transport (OHT) or average SSTs has been found. In this study, look further into drivers consequences of compared simulations PlioMIP2. We find all model closed Bering Strait Canadian Archipelago reduced freshwater Arctic Ocean Atlantic. This contributes increase salinity subpolar Labrador can mid-Pliocene. To investigate dynamics behind ensemble's variable response total OHT AMOC, separate two components associated overturning circulation wind-driven gyre circulation. While mean component increased significantly magnitude mid-Pliocene, it partly compensated by reduction northern subtropical region. indicates lack due changes gyre. should therefore considered separately gain more complete understanding AMOC. addition, exerts influence on pre-industrial, providing possible explanation for improved agreement PlioMIP2 reconstructions