What Earth's gravity reveals about climate change

[Jim__]

From phys.org:

On March 17, 2002, the German-U.S. satellite duo GRACE (Gravity Recovery and Climate Experiment) was launched to map the global gravitational field with unprecedented precision. The mission lasted 15 years, more than three times as long as expected. When the two satellites burned up in the Earth's atmosphere at the end of 2017 and beginning of 2018, they had recorded the Earth's gravitational field and its changes over more than 160 months.

This so-called time-resolved satellite gravimetry makes it possible, among other things, to monitor the terrestrial water cycle, the mass balance of ice sheets and glaciers, and sea level change, and thus to better understand the mechanisms of the global climate system, precisely assess important climatic trends, and to predict possible consequences.

...

GRACE produced the first-ever direct measurement of ice-mass loss from ice sheets and glaciers. Previously, it had only been possible to estimate the masses and their changes using indirect methods. Within the first two years of the mission, it was already possible to observe clear signals of ice-mass loss in Greenland and Antarctica. The measured data showed that 60 percent of the total mass loss is due to enhanced melt production in response to Arctic warming trends, while 40 percent is due to an increase of ice flow into the ocean. According to GRACE data, between April 2002 and June 2017, Greenland lost about 260 billion tons of ice per year, Antarctica about 140 billion tons. In addition to long-term trends, the gravity field data also provide evidence of the direct effects of global climate phenomena such as El Niño on ice sheets and glaciers worldwide.

...

Among the most impactful contributions of the GRACE mission has been the unveiling of Earth's changing freshwater landscape, which has profound implications for water, food and human security. Global estimates of GRACE trends suggest increasing water storage in high and low latitudes, with decreased storage in mid-latitudes. Though the GRACE record is relatively short, this observation of large-scale changes in the global hydrological cycle has been an important early confirmation of the changes predicted by climate models through the 21st century.

more ...

[Ghost Dog]

1. ... Nice instruments ...

... The greater the mass of an object, the greater its gravitational attraction. For example, the Alps exert a higher gravitational pull than the North German lowlands. When satellites orbit the Earth and fly over a massive region, they accelerate minimally when approaching it and slow down as they fly away.

A tiny part of the gravitation emanating from the Earth is based on water on or near the surface in oceans, rivers, lakes, glaciers and underground. This water reacts to seasons, storms, droughts or other weather effects. GRACE took advantage of the mass displacement of water by recording its effect on the satellite duo that orbited Earth 220 kilometres in a row. Microwaves were used to measure their distance. This distance changed over time due to the mass shift on Earth. From the data, the researchers then calculated monthly maps of the regional changes in the Earth's gravitational pull and the causal changes in the masses on the surface...

https://phys.org/news/2019-04-earth-gravity-reveals-climate.html