Ekman transport and upwelling during Younger Dryas estimated from wind stress from GENESIS Climate model experiments with variable North Atlantic heat convergence

Reconstructed climatic changes during the Younger Dryas interval are similar to, but somewhat larger and more wide‐spread than, those expected based on the direct atmospheric effects of reduced North Atlantic oceanic heat transport. The paleoclimatic data show that North Atlantic cooling during the Younger Dryas was accompanied by stronger winds in many regions, suggesting that enhanced wind‐driven ocean upwelling may have served as a positive feedback on the cooling. We test this hypothesis using the GENESIS atmospheric general circulation model, and find that Younger Dryas‐age specified reduction in North Atlantic oceanic heat transport increases tropical Ekman divergence by ≈10% in regions and at times of prominent upwelling, sufficient to affect tropical temperatures.

[1]  R. Alley,et al.  THE DEGLACIATION OF THE NORTHERN HEMISPHERE: A Global Perspective , 1999 .

[2]  A. M. Ágústsdóttir.  Abrupt climate changes and the effects of North Atlantic deepwater formation: Results from the GENESIS global climate model and comparison with data from the Younger Dryas event and the event at 8200 years bp and the present , 1998 .

[3]  S. Philander,et al.  The role of ocean-atmosphere interactions in tropical cooling during the last glacial maximum , 1998, Science.

[4]  Alan C. Mix,et al.  Millennial-scale deep water oscillations: Reflections of the North Atlantic in the deep Pacific from 10 to 60 ka , 1998 .

[5]  Stefan Rahmstorf,et al.  Simulation of modern and glacial climates with a coupled global model of intermediate complexity , 1998, Nature.

[6]  T. Stocker,et al.  Timing of the Antarctic cold reversal and the atmospheric CO2 increase with respect to the Younger Dryas Event , 1997 .

[7]  R. Thunell,et al.  Tropical Pacific sea surface temperatures and upper water column thermal structure during the Last Glacial Maximum , 1997 .

[8]  Thomas F. Stocker,et al.  Influence of CO2 emission rates on the stability of the thermohaline circulation , 1997, Nature.

[9]  A. Mix,et al.  Spatial and temporal oceanographic variability of the eastern equatorial Pacific during the Late Pleistocene: Evidence from radiolaria microfossils , 1997 .

[10]  A. Ravelo,et al.  Tropical Pacific Ocean thermocline depth reconstructions for the Last Glacial Maximum , 1997 .

[11]  David Pollard,et al.  Greenland and Antarctic Mass Balances for Present and Doubled Atmospheric CO2 from the GENESIS Version-2 Global Climate Model , 1997 .

[12]  R. Alley,et al.  The Younger Dryas Termination and North Atlantic Deep Water Formation: Insights from climate model simulations and Greenland Ice Cores , 1997 .

[13]  J. Overpeck,et al.  Rapid climate changes in the tropical Atlantic region during the last deglaciation , 1996, Nature.

[14]  J. Kennett,et al.  Brief interstadial events in the Santa Barbara basin, NE Pacific, during the past 60 kyr , 1996, Nature.

[15]  Richard B. Alley,et al.  Large Arctic Temperature Change at the Wisconsin-Holocene Glacial Transition , 1995, Science.

[16]  D. Pollard,et al.  A Global Climate Model (GENESIS) with a Land-Surface Transfer Scheme (LSX). Part I: Present Climate Simulation. , 1995 .

[17]  W. Peltier,et al.  Ice Age Paleotopography , 1994, Science.

[18]  D. Rea.  The paleoclimatic record provided by eolian deposition in the deep sea: The geologic history of wind , 1994 .

[19]  C. McClain,et al.  An investigation of Ekman upwelling in the North Atlantic , 1993 .

[20]  Thomas F. Stocker,et al.  A Zonally Averaged, Coupled Ocean-Atmosphere Model for Paleoclimate Studies , 1992 .

[21]  T. Crowley.  North Atlantic Deep Water cools the southern hemisphere , 1992 .

[22]  J. Overpeck,et al.  A high-resolution late Quaternary upwelling record from the anoxic Cariaco Basin, Venezuela , 1991 .

[23]  James B. Brown,et al.  Physical and biological processes in the North Atlantic during the first GARP Global Experiment , 1990 .

[24]  J. Hansen,et al.  The ice-core record: climate sensitivity and future greenhouse warming , 1990, Nature.

[25]  F. Street-Perrott,et al.  Abrupt climate fluctuations in the tropics: the influence of Atlantic Ocean circulation , 1990, Nature.

[26]  W. Broecker,et al.  The role of ocean-atmosphere reorganizations in glacial cycles , 1989 .

[27]  A. Mix,et al.  Late Quaternary paleoceanography of the tropical Atlantic, 2: The seasonal cycle of sea surface temperatures, 0–20,000 years B.P. , 1986 .

[28]  A. Mix,et al.  Late Quaternary Paleoceanography of the Tropical Atlantic, 1: Spatial Variability of Annual Mean Sea-Surface Temperatures, 0-20,000 Years B.P. , 1986 .

[29]  Sol Hellerman,et al.  Normal Monthly Wind Stress Over the World Ocean with Error Estimates , 1983 .

[30]  E. Hofmann,et al.  Wind Generation of the Costa Rica Dome , 1981, Science.

[31]  P. Müller,et al.  Productivity, sedimentation rate, and sedimentary organic matter in the oceans—I. Organic carbon preservation , 1979 .

[32]  A. Leetmaa,et al.  Updated charts of the mean annual wind stress, convergences in the Ekman layers, and Sverdrup transports in the North Atlantic , 1978 .

[33]  D. Pollard,et al.  Climate and ice-sheet mass balance at the last glacial maximum from the GENESIS version 2 global climate model , 1997 .