Greenland's ice sheet is melting, Earth's becoming a waterworld

The vast Greenland ice sheet is made up of compressed layers of snow from 100,000 years to the present time. It's presence acts as both a valuable record of our past climate changes and an indicator for future changes as well.

From a new research involving University College London (UCL) academics, over the past 40 years, Greenland's extreme ice melting has become more frequent and intense caused by global warming. This has resulted to increased sea levels and the risk of floods worldwide. For the past decade alone, there has been 3.5 trillion tons of ice that melted from Greenland’s surface and flowed into the ocean - an amplitude to submerge the United Kingdom with around 15 meters of meltwater, or all of New York City. The new study which is published in Nature Communications is the first to use satellite data from space to detect the phenomenon known as ice sheet runoff. The study used measurements from the European Space Agency’s CryoSat-2 satellite mission, using estimates of surface elevation change over time. One of the very few satellites orbiting within 2 degrees of the planet's poles, CryoSat-2 has provided scientists with a long history of data no other spacecraft could reach since its launch over 11 years ago, transforming scientists' capacity to study the polar regions. It remains a key contributor to research and knowledge critical to decision-making on the planet’s health. The co-author of the study Lin Gilbert (UCL Mullard Space Science Laboratory) stated: “Observations show that extreme melt events in Greenland have become more frequent and more intense - as well as more erratic - which is a global problem. Monitoring from space enables us to cover the whole of Greenland (and nearly all of Antarctica) repeatedly, which can't be done by teams on the ground. This is the first-time run-off has ever been measured directly from space - allowing us to remotely observe hard-to-explore regions of the ice sheets and use these observations to form an enhanced understanding of why this is happening and what we can do about it in future”. The international team of researchers found that over the past four decades Greenland’s meltwater runoff has risen by 21% - and has become 60% more erratic from one summer to the next heightening the risk of flooding worldwide and disrupting marine ecosystems in the Arctic Ocean. Raising sea levels can also alter patterns of ocean and atmospheric circulation that affect weather conditions across the globe. These changes are related to extreme weather events such as heatwaves, which have become more frequent and are now a major cause of ice loss from Greenland. Lead author Dr. Thomas Slater (University of Leeds) said: “As we’ve seen with other parts of the world, Greenland is also vulnerable to an increase in extreme weather events. As our climate warms, it’s reasonable to expect that the instances of extreme melting in Greenland will happen more often – observations such as these are an important step in helping us to improve climate models and better predict what will happen this century.” “There are, however, reasons to be optimistic. We know that setting and meeting meaningful targets to cut emissions could reduce ice losses from Greenland by a factor of three, and there is still time to achieve this.” The observations of this study can assist to verify on how climate models simulate ice sheet melting. This guides in improving future predictions of how much Greenland will raise the global sea level as extreme weather events become more common. Study co-author Dr Amber Leeson (Lancaster University) said: “Model estimates suggest that the Greenland ice sheet will contribute between about 3 - 23cm to global sea level rise by 2100. This prediction has a wide range, in part because of uncertainties associated with simulating complex ice melt processes, including those associated with extreme weather. “These new spaceborne estimates of runoff will help us to understand these complex ice melt processes better, improve our ability to model them, and thus enable us to refine our estimates of future sea level rise.”

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