Changes in Boreal Lakes have Broad Climate Impacts

Summary

Climate change may alter lake area and cause other changes in high-latitude, terrestrial-surface properties, which, in turn, affect climate. BER scientists at Lawrence Berkeley National Laboratory (LBNL) and Lawrence Livermore National Laboratory used a lake model, recently developed at LBNL, in the Community Land Model (CLM4-LISSS) and coupled into the Community Earth System Model. This new version corrected a previous underestimation of lake area under present conditions and predicted spring cooling and fall warming of 1°C throughout large areas of Canada and the United States. The predicted diurnal temperature range decreased by up to 4°C in the summer, bringing predictions closer to observations. A projected loss of lakes in some permafrost regions under doubled CO₂ slightly enhanced net daytime warming in those regions. Correcting the under-estimation of mainly boreal lake area caused changes in distant Southern Ocean winds, which play an important role in the carbon cycle driving CO₂ upwelling from the deep ocean into the atmosphere. These changes were also analyzed in an idealized ocean-only “aqua-planet” model with prescribed sea-surface temperatures for which relatively small (2°C) decreases in high-latitude surface temperatures caused shifts in the Inter-Tropical Convergence Zone and Southern Ocean winds. The improved CLM lake model represents an important step forward in simulating potential climate feedbacks in high-latitude systems. In addition to atmospheric interactions, changes in inundation and thermokarst lakes can lead to potentially important changes in surface greenhouse gas emissions.

References

Subin, Z. M., L. N. Murphy, F. Li, C. Bonfils, and W. J. Riley. 2012. “Boreal Lakes Moderate Seasonal and Diurnal Temperature Variation and Perturb Atmospheric Circulation: Analyses in CESM1,” Tellus A 64, 15639. DOI: 10.3402/tellusa.v64i0.15639.

Subin, Z. M., W. J. Riley, and D. Mironov. 2012. “An Improved Lake Model for Climate Simulations: Model Structure, Evaluation, and Sensitivity Analyses in CESM1,” Journal of Advances in Modeling Earth Systems 4, M02001. DOI: 10.1029/2011MS000072.