scholarly journals Atlantic Ocean circulation changes preceded millennial tropical South America rainfall events during the last glacial

2015 ◽  
Vol 42 (2) ◽  
pp. 411-418 ◽  
Author(s):  
Pierre Burckel ◽  
Claire Waelbroeck ◽  
Jeanne Marie Gherardi ◽  
Sylvain Pichat ◽  
Helge Arz ◽  
...  
Keyword(s):  
South America ◽  
Atlantic Ocean ◽  
Ocean Circulation ◽  
Rainfall Events ◽  
Last Glacial ◽  
Circulation Changes ◽  
The Last Glacial ◽  
Tropical South America

scholarly journals Limited response of peatland CH<sub>4</sub> emissions to abrupt Atlantic Ocean circulation changes in glacial climates

2013 ◽  
Vol 9 (3) ◽  
pp. 3519-3561 ◽  
Author(s):  
P. O. Hopcroft ◽  
P. J. Valdes ◽  
R. Wania ◽  
D. J. Beerling
Keyword(s):  
Atlantic Ocean ◽  
Ocean Circulation ◽  
Ice Core ◽  
Meridional Overturning Circulation ◽  
Model Simulations ◽  
Ch4 Emissions ◽  
Last Glacial ◽  
Time Periods ◽  
Circulation Changes ◽  
The Last Glacial

Abstract. Ice-core records show that abrupt Dansgaard-Oeschger climatic warming events of the last glacial period were accompanied by large increases in the atmospheric CH4 concentration (up to 200 ppbv). These abrupt changes are generally regarded as arising from the effects of changes in the Atlantic Ocean meridional overturning circulation and the resultant climatic impact on natural CH4 sources, in particular wetlands. We use two different ecosystem models of wetland CH4 emissions to simulate northern CH4 sources forced with coupled general circulation model simulations of five different time periods during the last glacial to investigate the potential influence of abrupt ocean circulation changes on atmospheric CH4 levels during D-O events. The simulated warming over Greenland of 7–9 °C in the different time-periods is at the lower end of the range of 11–15 °C derived from ice-cores, but is associated with strong impacts on the hydrological cycle, especially over the North Atlantic and Europe during winter. We find that although the sensitivity of CH4 emissions to the imposed climate varies significantly between the two ecosystem emissions models, the model simulations do not reproduce sufficient emission changes to satisfy ice-core observations of CH4 increases during abrupt events. This suggests that alternative scenarios of climatic change could be required to explain the abrupt glacial CH4 variations.

scholarly journals Limited response of peatland CH<sub>4</sub> emissions to abrupt Atlantic Ocean circulation changes in glacial climates

2014 ◽  
Vol 10 (1) ◽  
pp. 137-154 ◽  
Author(s):  
P. O. Hopcroft ◽  
P. J. Valdes ◽  
R. Wania ◽  
D. J. Beerling
Keyword(s):  
Atlantic Ocean ◽  
Ocean Circulation ◽  
Ice Core ◽  
Meridional Overturning Circulation ◽  
Model Simulations ◽  
Ch4 Emissions ◽  
Last Glacial ◽  
Time Periods ◽  
Circulation Changes ◽  
The Last Glacial

Abstract. Ice-core records show that abrupt Dansgaard–Oeschger (D–O) climatic warming events of the last glacial period were accompanied by large increases in the atmospheric CH4 concentration (up to 200 ppbv). These abrupt changes are generally regarded as arising from the effects of changes in the Atlantic Ocean meridional overturning circulation and the resultant climatic impact on natural CH4 sources, in particular wetlands. We use two different ecosystem models of wetland CH4 emissions to simulate northern CH4 sources forced with coupled general circulation model simulations of five different time periods during the last glacial to investigate the potential influence of abrupt ocean circulation changes on atmospheric CH4 levels during D–O events. The simulated warming over Greenland of 7–9 °C in the different time periods is at the lower end of the range of 11–15 °C derived from ice cores, but is associated with strong impacts on the hydrological cycle, especially over the North Atlantic and Europe during winter. We find that although the sensitivity of CH4 emissions to the imposed climate varies significantly between the two ecosystem emissions models, the model simulations do not reproduce sufficient emission changes to satisfy ice-core observations of CH4 increases during abrupt events. The inclusion of permafrost physics and peatland carbon cycling in one model (LPJ-WHyMe) increases the climatic sensitivity of CH44 emissions relative to the Sheffield Dynamic Global Vegetation Model (SDGVM) model, which does not incorporate these processes. For equilibrium conditions this additional sensitivity is mostly due to differences in carbon cycle processes, whilst the increased sensitivity to the imposed abrupt warmings is also partly due to the effects of freezing on soil thermodynamics. These results suggest that alternative scenarios of climatic change could be required to explain the abrupt glacial CH4 variations, perhaps with a more dominant role for tropical wetland CH4 sources.

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