Rei Chemke

(Columbia University)

The climate’s response to anthropogenic emissions: the role of ocean circulation

When Oct 10, 2018
from 03:30 pm to 04:30 pm
Where John Cahir Auditorium 112 Walker Building
Contact Name Steven Feldstein
Contact email
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Rei Chemke Columbia

The effects of ocean circulation on the climate’s response to anthropogenic emissions at low and high latitudes are examined. At low latitudes, the Hadley cell plays an important role in setting the strength and position of the hydrological cycle. Climate projections show a weakening of the Hadley cell, together with widening of its vertical and meridional extents. These changes are projected to have profound global climatic impacts. Current theories for the Hadley cell response to increased greenhouse gases account only for atmospheric and oceanic thermodynamic changes, but not for oceanic circulation changes. Here, the effects of ocean circulation changes on the Hadley cell response to increased greenhouse gases are examined. First, using a hierarchy of ocean-model configurations under increased greenhouse gases or arctic sea-ice loss, we show that, by cooling the surface and atmosphere, ocean circulation contracts and strengthens the Hadley cell, and thus reduces its projected response. We next examine the role of ocean circulation in cooling the North Atlantic in recent years (the North Atlantic warming hole). Using observations and large ensemble simulations, we find that since the beginning of 21st century there has been a reduction in surface meridional heat advection, which cools the North Atlantic midlatitudes and is part of an emerged forced response to anthropogenic emissions and not of internal climate variability.