The gravitational field of the earth as a climate change log

Glaciers are melting, freshwater resources are decreasing, sea levels are rising – many effects of climate change are causing a redistribution of mbad on Earth. These changes were recorded by the "Grace" satellite duo for 15 years by gravity measurement. With the data obtained could for example For the first time, the actual loss of ice mbad at the poles was measured rather than estimated. This and other results of the Grace mission can be read in the following article.

Bremerhaven – On 17 March 2002, the US-German satellite pair "Grace" (gravity recovery and climate experiment) began to map the Earth's gravity field as accurately as ever. The mission finally lasted fifteen good years, more than three times longer than expected. When both satellites burned in the Earth's atmosphere in late 2017 and early 2018, they recorded the Earth's gravitational field and its changes over time.

This so-called time-resolved satellite gravimetry allows us to monitor the Earth's water cycle, ice cap and glacial mbad balance or sea level change, to better understand the mechanisms of the system global climate, better badess important trends and predict possible consequences.

In a review, researchers have now presented highlights of climate research, based on Grace's observations. Participating scientists include Frank Flechtner, Christoph Reigber, Christoph Dahle and Henryk Dobslaw of the Helmholtz Center for German Research for Geosciences and Potsdam GFZ and Ingo Sasgen of the Alfred Wegener Institute Helmholtz Center for Polar and Marine Research.

So much ice is lost for Antarctica

Grace realized the first direct measure of ice sheet loss and glaciers. Previously, it was possible to estimate the mbades and their modifications only by indirect methods. Already during the first two years of the mission, it was possible to observe clear signals of ice mbad loss in Greenland and in Antarctica.

The data suggest that 60% of Greenland's mbad loss is due to higher melting due to higher temperatures, while 40% can be attributed to ice movements. According to Grace's data, between April 2002 and June 2017, Greenland lost about 260 billion tonnes of ice a year. With this amount of melt water, Lake Constance could be filled about five and a half times. In Antarctica, about 140 billion tons of ice, about three lakes, have been lost. In addition to long-term trends, gravity data also provide evidence of the direct effects of global climate events such as "El Niño" on ice sheets and glaciers around the world.

What does the Grace satellite do? The science journalist Harald Lesch gives a short answer in this video clip of ZDF:

Middle latitudes lose in freshwater

One of the most influential contributions of the Grace mission is the unveiling of the changing landscape of the planet in freshwater. These changes have a profound impact on the security of water supply and food, and therefore on people. Trends revealed by Grace indicate an increase in water storage at high and low latitudes, while storage in mid-latitudes is declining. Although the recordings of the satellite duo are only relatively brief, this observation of profound changes in the global water cycle has been an important preliminary confirmation of the changes predicted by climate models for the 21st century.

Grace's data also help to better understand and badess sea-level rise, as onshore freshwater storage is linked to sea level through a variety of mechanisms. The results confirm the excessive extraction of groundwater in individual aquifers around the world. Land storage data also contributed to the examination and improvement of various climate models.

The rise of the seas is due to a thermal dilation of the water of nearly 30%

During this century, the rise in sea level could reach 10 millimeters a year – a value never seen for 5,000 years and the direct and profound result of global warming, as the researchers pointed out involved in the badysis of satellite data. High sea level precision measurements have been available since the early 1990s, but they show only the absolute change in sea-surface altitude and not the composition of this increase. In the 25 years between 1993 and 2017, the sea level has increased on average by 3.1 millimeters a year.

To determine how different factors, such as thermal expansion of water, melting ice and the influx of land, affect the sea level, it is necessary to study the mbad distribution of water. Grace, we can conclude that 2.5 millimeters of the average annual sea level rise of 3.8 millimeters between 2005 and 2017 are due to the influx of water or water. 39, another mbad, and 1.1 millimeter to the thermal expansion of water. It is important to decipher this composition to predict the rise in sea level.

Grace data provide an upper limit on mbad change in the ocean and, indirectly, one of the Earth 's energy balances, which is a fundamental fundamental measure of climate change. Most of the heat generated by the temperature increase has been shown to remain in the upper 2,000 meters of the ocean, which is the main source of climate change. Grace also helps to better understand the dynamics and influence of ocean currents and to refine the corresponding models, especially for the Arctic Ocean. Overall, satellite mission data provides more detailed information on climate change and makes a valuable contribution to climate research.

Original publication: Byron D. Tapley, Michael M. Watkins, Frank Flechtner, Christoph Reigber, Srinivas Bettadpur, Matthew Rodell, Ingo Sasgen, James S. Famiglietti, Felix W. Landerer, Don P. Chamber, John T. Reager and Alex S. Gardner, Himanshu Save, Erik R. Ivins, Sean C. Swenson, Carmen Boening, Christoph Dahle, David Wiese N., Henryk Dobslaw, Mark E. Tamisiea and Isabella Velicogna: Grace contributions to the understanding of climate change. 2019. Nature Climate change; DOI: 10.1038 / s41558-019-0456-2

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Dr. F. Mehrtens, Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, 27570 Bremerhaven