Ice-sheet modulation of deglacial North American monsoon intensification

Tripti Bhattacharya, Jessica E. Tierney, Jason A. Addison, James W. Murray

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The North American monsoon, the dominant source of rainfall for much of the arid US Southwest, remains one of the least understood monsoon systems. The late Pleistocene evolution of this monsoon is poorly constrained, largely because glacial changes in winter rainfall obscure summer monsoon signatures in many regional proxy records. Here, we develop deglacial records of monsoon strength from isotopic analyses of leaf wax biomarkers in marine sediment cores. Reconstructions indicate a regional decrease in monsoon rainfall during the Last Glacial Maximum, and that the deglacial trajectory of the North American monsoon closely tracks changes in North American ice cover. In climate model simulations, North American ice cover shifts the westerlies southwards, favouring the mixing of cold, dry air into the US Southwest. This process, known as ventilation, weakens the monsoon by diluting the energy fluxes required for convection. As the ice sheet retreats northwards, the monsoon strengthens, and local ocean conditions may play a larger role in regulating its intensity. We conclude that on glacial–interglacial timescales, ice-sheet-induced reorganizations of atmospheric circulation have a dominant influence on the North American monsoon.

Original languageEnglish (US)
JournalNature Geoscience
DOIs
StateAccepted/In press - Jan 1 2018

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ice sheet
monsoon
ice cover
rainfall
wax
energy flux
Last Glacial Maximum
atmospheric circulation
marine sediment
ventilation
sediment core
biomarker
climate modeling
convection
trajectory
Pleistocene
timescale
winter
air
ocean

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

Cite this

Ice-sheet modulation of deglacial North American monsoon intensification. / Bhattacharya, Tripti; Tierney, Jessica E.; Addison, Jason A.; Murray, James W.

In: Nature Geoscience, 01.01.2018.

Research output: Contribution to journalArticle

Bhattacharya, Tripti ; Tierney, Jessica E. ; Addison, Jason A. ; Murray, James W. / Ice-sheet modulation of deglacial North American monsoon intensification. In: Nature Geoscience. 2018.
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