Boreal lakes moderate seasonal and diurnal temperature variation and perturb atmospheric circulation: Analyses in the Community Earth System Model 1 (CESM1)
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Div.
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Program for Climate Model Diagnosis and Intercomparison
We used a lake thermal physics model recently coupled into the Community Earth System Model 1 (CESM1) to study the effects of lake distribution in present and future climate. Under present climate, correcting the large underestimation of lake area in CESM1 (denoted CCSM4 in the configuration used here) caused 1 °C spring decreases and fall increases in surface air temperature throughout large areas of Canada and the US. Simulated summer surface diurnal air temperature range decreased by up to 4 °C, reducing CCSM4 biases. These changes were much larger than those resulting from prescribed lake disappearance in some present-day permafrost regions under doubled-CO2 conditions. Correcting the underestimation of lake area in present climate caused widespread high-latitude summer cooling at 850 hPa. Significant remote changes included decreases in the strength of fall Southern Ocean westerlies. We found significantly different winter responses when separately analysing 45-yr subperiods, indicating that relatively long simulations are required to discern the impacts of surface changes on remote conditions. We also investigated the surface forcing of lakes using idealised aqua-planet experiments which showed that surface changes of 2 °C in the Northern Hemisphere extra-tropics could cause substantial changes in precipitation and winds in the tropics and Southern Hemisphere. Shifts in the Inter-Tropical Convergence Zone were opposite in sign to those predicted by some previous studies. Zonal mean circulation changes were consistent in character but much larger than those occurring in the lake distribution experiments, due to the larger magnitude and more uniform surface forcing in the idealised aqua-planet experiments.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 1182742
- Report Number(s):
- LBNL-5451E
- Journal Information:
- Tellus. Series A, Dynamic Meteorology and Oceanography, Vol. 64, Issue 0; ISSN 1600-0870
- Publisher:
- International Meteorological Inst.
- Country of Publication:
- United States
- Language:
- English
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