New Columbia Engineering study—first to investigate the long-term effect of soil moisture-atmosphere feedbacks in drylands—finds that soil moisture exerts a negative feedback on surface water availability in drylands, offsetting some of the expected decline.
New Columbia Engineering study—first to investigate the long-term effect of soil moisture-atmosphere feedbacks in drylands—finds that soil moisture exerts a negative feedback on surface water availability in drylands, offsetting some of the expected decline.
Scientists have thought that global warming will increase the availability of surface water—freshwater resources generated by precipitation minus evapotranspiration—in wet regions, and decrease water availability in dry regions. This expectation is based primarily on atmospheric thermodynamic processes. As air temperatures rise, more water evaporates into the air from the ocean and land. Because warmer air can hold more water vapor than dry air, a more humid atmosphere is expected to amplify the existing pattern of water availability, causing the “dry-get-drier, and wet-get-wetter” atmospheric responses to global warming.
A Columbia Engineering team led by Pierre Gentine, Maurice Ewing and J. Lamar Worzel professor of earth and environmental engineering and affiliated with the Earth Institute, wondered why coupled climate model predictions do not project significant “dry-get-drier” responses over drylands, tropical and temperate areas with an aridity index of less than 0.65, even when researchers use the high emissions global warming scenario. Sha Zhou, a postdoctoral fellow at Lamont-Doherty Earth Observatory and the Earth Institute who studies land-atmosphere interactions and the global water cycle, thought that soil moisture-atmosphere feedbacks might play an important part in future predictions of water availability in drylands.
The new study, published today by Nature Climate Change, is the first to show the importance of long-term soil moisture changes and associated soil moisture-atmosphere feedbacks in these predictions. The researchers identified a long-term soil moisture regulation of atmospheric circulation and moisture transport that largely ameliorates the potential decline of future water availability in drylands, beyond that expected in the absence of soil moisture feedbacks.
Read more at Columbia University School of Engineering and Applied Science
Photo Credit: Leolo212 via Pixabay
