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Tracking the Strength of the Walker Circulation With Stable Isotopes in Water Vapor
Author(s) -
Dee Sylvia G.,
Nusbaumer Jesse,
Bailey Adriana,
Russell James M.,
Lee JungEun,
Konecky Bronwen,
Buenning Nikolaus H.,
Noone David C.
Publication year - 2018
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2017jd027915
Subject(s) - environmental science , climatology , troposphere , water vapor , water cycle , atmospheric sciences , precipitation , walker circulation , convection , atmospheric circulation , climate model , forcing (mathematics) , climate change , flux (metallurgy) , water mass , mass flux , global warming , sea surface temperature , meteorology , geology , chemistry , oceanography , geography , ecology , physics , organic chemistry , biology , mechanics
General circulation models (GCMs) predict that the global hydrological cycle will change in response to anthropogenic warming. However, these predictions remain uncertain, in particular for precipitation [IPCC, 2013]. Held and Soden [2006] suggest that as lower-tropospheric water vapor concentration increases in a warming climate, the atmospheric circulation and convective mass fluxes will weaken. Unfortunately, this process is difficult to constrain, as convective mass fluxes are poorly observed and incompletely simulated in GCMs. Here, we demonstrate that stable hydrogen isotope ratios in tropical atmospheric water vapor can trace changes in temperature, atmospheric circulation and convective mass flux in a warming world. We evaluate changes in temperature, the distribution of water vapor, vertical velocity ( ω ) and advection, and water isotopes in vapor ( δD V ) in water isotopeenabled GCM experiments for modern vs. high CO 2 atmospheres to identify spatial patterns of circulation change over the tropical Pacific. We find that slowing circulation in the tropical Pacific moistens the lower troposphere and weakens convective mass flux, both of which impact the δD of water vapor in the mid-troposphere. Our findings constitute a critical demonstration of how water isotope ratios in the tropical Pacific respond to changes in radiative forcing and atmospheric warming. Moreover, as changes in δD V can be observed by satellites, our results develop new metrics for the detection of global warming impacts to the hydrological cycle and, specifically, the strength of the Walker Circulation.