- 2370 - When you hear about ice loss from Greenland or Antarctica how do we know that? When we hear about the aquifer in California getting depleted how do we measure that? How do we know there is a new explanation for a wobble in Earth's rotation. You might be surprised that the measurements are made by satellite.
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--------------------- 2370 - GRACE - a new satellite measurement
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- The satellite is the Gravity Recovery and Climate Experiment (GRACE).
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- GRACE data, collected from 2002 to 2017, are still being used to improve our understanding of water in motion and its sometimes surprising effects on our planet.
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- Water is an important sign of the health of the planet. But water is hard to track in some forms such as polar ice or water stored deep underground. Scientists have used this increased knowledge from satellite measurements to learn how water moves and is stored on Earth. This helps us understand our global climate and how it is changing.
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- The GRACE mission was to gather laser and gravity measurements to learn how climate change affects water stored in the ocean, the ice and on the continents.
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- For example we learned that Greenland has lost 258 gigatons of ice per year, with the amount varying by more than 50% from year to year. This was due to a large extent in response to temperatures during the summer months. The Arctic is warming about twice as fast as the global average, with ice-mass loss and sea level rise being the major consequences.
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- This data was used to budget each month the mass loss of glaciers and ice sheets around the world. It has dramatically improved our understanding of the processes at play in these remote areas and their sensitivity to climate change.
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- Antarctica lost 137 gigatons per year on average, but the annual rate of loss varied by more than 200%, mainly due to fluctuations in snowfall. GRACE also found that these large fluctuations mostly occur in West Antarctica and correlate well with El Niño events, which affect how much precipitation reaches the continent.
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- Changes in water storage on land has revealed that less water is now being stored naturally in mid-latitude land regions. These regions are getting less precipitation and are becoming drier. More water is being stored in high- and low-latitude regions because those regions are getting wetter. Climate models have long predicted that global climate change will bring about this trend.
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- Sea levels rose more than 1.5 inches per decade on average over the globe from 2005 to 2016. The two main causes for this change were runoff from melting ice sheets and glaciers, and expansion of the ocean water itself as its temperature rises.
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- Besides monitoring changes in the ice sheets and glaciers, GRACE could detect how much sea level rise was due to water formerly locked in ice on land being added to the ocean. The data show that this source increased throughout the mission and is currently responsible for about two-thirds of sea level rise.
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- GRACE provided a paradigm shift in our view of how the oceans, atmosphere and land surface components interact. It showed that the water leaving the polar ice caps is equal to the increase in water mass in the oceans, giving confirmation of this important measurement's use in assessing ocean heat storage.
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- GRACE is also an important asset for assessing the state of freshwater and assisting in managing it. GRACE data to look at soil saturation levels weeks before flood season. Researchers have found that knowledge of unusually high levels of underground water storage can increase the lead time on warnings of peak river flooding by up to six weeks.
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- A new satellite that is a successor was launched in May 2018. GRACE-FO has completed all of its checkout phases and will soon begin releasing monthly maps of mass changes on Earth just like its predecessor.
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- Space missions are helping us learn more about our own planet. Making good decisions with good data.
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- May 17, 2019.
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--------------------- Friday, May 17, 2019 -------------------------
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