Why Does Global Warming Weaken the Gulf Stream but Intensify the Kuroshio?

• Published in: Journal of climate Vol. 32; no. 21; pp. 7437 - 7451
• Main Authors: Chen, Changlin, Wang, Guihua, Xie, Shang-Ping, Liu, Wei
• Format: Journal Article
• Language: English
• Published: Boston American Meteorological Society 01.11.2019
• Subjects: 21st century; Advection; Atlantic Meridional Overturning Circulation (AMOC); Boundary currents; Climate; Climate change; Experiments; General circulation models; Global warming; Gulf Stream; Heat; Heat transport; Meridional heat transport; Ocean circulation; Ocean currents; Ocean warming; Oceanic general circulation model; Oceans; Offshore; Rivers; Salinity; Sea level; Sea level changes; Sea level rise; Sea surface; Sea surface warming; Simulation; Subduction; Surface salinity; Surface temperature; Viscosity; Western boundary currents; Wind
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/jcli-d-18-0895.1

The Kuroshio and Gulf Stream, the subtropical western boundary currents of the North Pacific and North Atlantic, play important roles in meridional heat transport and ocean–atmosphere interaction processes. Using a multimodel ensemble of future projections, we show that a warmer climate intensifies the upper-layer Kuroshio, in contrast to the previously documented slowdown of the Gulf Stream. Our ocean general circulation model experiments show that the sea surface warming, not the wind change, is the dominant forcing that causes the upper-layer Kuroshio to intensify in a warming climate. Forced by the sea surface warming, ocean subduction and advection processes result in a stronger warming to the east of the Kuroshio than to the west, which increases the isopycnal slope across the Kuroshio, and hence intensifies the Kuroshio. In the North Atlantic, the Gulf Stream slows down as part of the Atlantic meridional overturning circulation (AMOC) response to surface salinity decrease in the high latitudes under global warming. The distinct responses of the Gulf Stream and Kuroshio to climate warming are accompanied by different regional patterns of sea level rise. While the sea level rise accelerates along the northeastern U.S. coast as the AMOC weakens, it remains close to the global mean rate along the East Asian coast as the intensifying Kuroshio is associated with the enhanced sea level rise offshore in the North Pacific subtropical gyre.