loading page

Clumped-isotope constraint on upper-tropospheric cooling during the Last Glacial Maximum
  • +3
  • Asmita Banerjee,
  • Laurence Y Yeung,
  • Lee Thomas Murray,
  • Xin Tie,
  • Jessica E. Tierney,
  • Allegra N. LeGrande
Asmita Banerjee
Rice University

Corresponding Author:[email protected]

Author Profile
Laurence Y Yeung
Rice University
Author Profile
Lee Thomas Murray
University of Rochester
Author Profile
Xin Tie
University of Rochester
Author Profile
Jessica E. Tierney
University of Arizona
Author Profile
Allegra N. LeGrande
NASA Goddard Institute for Space Studies and Center for Climate Systems Research
Author Profile

Abstract

Ice cores and other paleotemperature proxies, together with general circulation models, have provided information on past surface temperatures and the atmosphere’s composition in different climates. Little is known, however, about past temperatures at high altitudes, which play a crucial role in Earth’s radiative energy budget. Paleoclimate records at high-altitude sites are sparse, and the few that are available show poor agreement with climate model predictions. These disagreements could be due to insufficient spatial coverage, spatiotemporal biases, or model physics; new records that can mitigate or avoid these uncertainties are needed. Here, we constrain the change in upper-tropospheric temperature at the global scale during the Last Glacial Maximum (LGM) using the clumped-isotope composition of molecular oxygen trapped in polar ice cores. Aided by global three-dimensional chemical transport modeling, we exploit the intrinsic temperature sensitivity of the clumped-isotope composition of atmospheric oxygen to infer that the upper troposphere (5 – 15 km altitude, effective mean 10 – 11 km) was 4 – 10°C cooler during the LGM than during the late preindustrial Holocene. These results support a minor or negligible steepening of atmospheric lapse rates during the LGM, which is consistent with a range of climate model simulations. Proxy-model disagreements with other high-altitude records may stem from inaccuracies in regional hydroclimate simulation, possibly related to land-atmosphere feedbacks.
Aug 2022Published in AGU Advances volume 3 issue 4. 10.1029/2022AV000688