Study suggests parched Earth soaks up water, slowing sea level rise | Watts Up With That?

Is there anything global warming can’t do? Now it seems that there is so much global warming that it is slowing the rise of sea levels.

An artist’s depiction of the NASA GRACE satellites and the Earth’s gravity field. This material relates to a paper that appeared in the Feb. 12, 2016 issue of Science, published by AAAS. The paper, by J.T. Reager at Jet Propulsion Laboratory in Pasadena, CA, and colleagues was titled, “A decade of sea level rise slowed by climate-driven hydrology.”

As glaciers melt due to climate change, the increasingly hot and parched Earth is absorbing some of that water inland, slowing sea level rise, NASA experts said Thursday.

Satellite measurements over the past decade show for the first time that the Earth’s continents have soaked up and stored an extra 3.2 trillion tons of water in soils, lakes and underground aquifers, the experts said in a study in the journal Science.

This has temporarily slowed the rate of sea level rise by about 20 percent, it said.“We always assumed that people’s increased reliance on groundwater for irrigation and consumption was resulting in a net transfer of water from the land to the ocean,” said lead author J.T. Reager of NASA’s Jet Propulsion Laboratory. “What we didn’t realize until now is that over the past decade, changes in the global water cycle more than offset the losses that occurred from groundwater pumping, causing the land to act like a sponge — at least temporarily.”The global water cycle involves the flow of moisture, from the evaporation over the oceans to the fall of precipitation, to runoff and rivers that lead back into the ocean.  Just how much effect on sea level rise this kind of land storage would have has remained unknown until now because there are no land-based instruments that can measure such changes planet-wide.

The latest data came from a pair of NASA satellites launched in 2002 — known as the Gravity Recovery and Climate Experiment (GRACE). more here

Here is the Press release from the AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE

Land reservoirs helped offset sea level rise, study says

Recent increases in the storage of excess groundwater may be helping to offset sea level rise by as much as 15%, a new study finds. While the capacity of land to store water is known to be an important factor affecting sea level rise, the magnitude of its storage contributions are not fully understood. Land masses store water in numerous ways, though some human-induced changes — including to groundwater extraction, irrigation, impoundment in reservoirs, wetland drainage, and deforestation – are affecting this process, as are climate-driven changes in rainfall, evaporation, and runoff.

To gain more insights into how the land storage capacity may have changed over recent years, John Reager and colleagues analyzed satellite data from 2002 to 2014 that measure changes in gravity, and thus underlying changes in water storage. They combined this satellite data with estimates of mass loss of glaciers to determine what impact land water storage might have had on sea level change.

Their analysis suggests that during this timeframe, climate variability resulted in an increase of approximately 3,200 gigatons of water being stored in land. This gain partially offset water losses from ice sheets, glaciers, and groundwater pumping, slowing the rate of sea level rise by 0.71 ± 0.20 millimeters per year, the authors say. While a small portion of the increase in land water storage can be directly attributed to human activities – primarily, the filling of reservoirs – the authors note that climate is the key driver. The greatest changes in land water storage were associated with regional climate-driven variations in precipitation.

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The paper: http://science.sciencemag.org/content/351/6274/699

A decade of sea level rise slowed by climate-driven hydrologyJ. T. Reager, A. S. Gardner, J. S. Famiglietti, D. N. Wiese, A. Eicker, M.-H. Lo

By land or by sea

How much of an effect does terrestrial groundwater storage have on sea-level rise? Reager et al. used gravity measurements made between 2002 and 2014 by NASA’s Gravity Recovery And Climate Experiment (GRACE) satellites to quantify variations in groundwater storage. Combining those data with estimates of mass loss by glaciers revealed groundwater’s impact on sea-level change. Net groundwater storage has been increasing, and the greatest regional changes, both positive and negative, are associated with climate-driven variability in precipitation. Thus, groundwater storage has slowed the rate of recent sea-level rise by roughly 15%.

Science, this issue p. 699

Abstract

Climate-driven changes in land water storage and their contributions to sea level rise have been absent from Intergovernmental Panel on Climate Change sea level budgets owing to observational challenges. Recent advances in satellite measurement of time-variable gravity combined with reconciled global glacier loss estimates enable a disaggregation of continental land mass changes and a quantification of this term. We found that between 2002 and 2014, climate variability resulted in an additional 3200 ± 900 gigatons of water being stored on land. This gain partially offset water losses from ice sheets, glaciers, and groundwater pumping, slowing the rate of sea level rise by 0.71 ± 0.20 millimeters per year. These findings highlight the importance of climate-driven changes in hydrology when assigning attribution to decadal changes in sea level.