Glaciers are important components of the global cryosphere and serve as indicators of global warming and climate change. Currently, Earth’s land area is covered with 10% glacial ice, which includes ice caps, glaciers, and the ice sheets of Greenland and Antarctica. However, Greenland’s ice sheet is melting faster than previously thought. In the 20th century, the region lost over 9,000 billion tons of ice, which accounts for 25 millimeters of sea-level rise.
The National Snow and Ice Data Center (NSIDC) reported that the melting of the Greenland ice sheet for 2019 was the seventh-highest since 1978. Aside from experiencing a general increase in melting since 2000, melting was also observed in nearly 90% of the island in at least one day. Some of the key factors for surface mass loss and melting for Greenland last year include the exceptional persistence of anticyclonic conditions (high pressure) during the 2019 summer and low snowfall in the preceding fall-winter-spring.
In 2019, scientists from Ohio State University presented time-lapse satellite images dating back 34 years of about 200 glaciers on the island of Greenland at the annual meeting of the American Geophysical Union (AGU). The presentation was the first time images were shown to compare Greenland’s glacier retreat. "These glaciers are calving more ice into the ocean than they were in the past. We're finding this clear correlation where more retreat instigates greater discharge of ice,” Michaela King, who presented the research at AGU, said.
According to Science Daily, an American website that aggregates press releases and publishes lightly edited press releases about science, the researchers showed that Greenland's glaciers retreated about 3 miles (5 kilometers) between 1985 and 2018. Ice melting got even worse in 2000, when ice calving began to increase. In recent years, the data revealed that 50 gigatons more ice per year calves into the ocean than what scientists observed before 2000.
"The ice sheet is out of balance," King said.
Aside from Greenland, the Antarctic is also undergoing an accelerated meltdown. Reports show that the region is losing six times as much ice as it was four decades ago. Its ice loss averaged 252 billion tons a year over the past decade. This is also happening in western North America’s glaciers, where ice loss quadrupled since the early 2000s to 12.3 billion tons annually.
Greenland Lost 11 Billion Tons of Ice in One Day
In 2012, 97% of Greenland’s ice sheet experienced melting, representing the worst melting since the ice sheets were monitored. Last year, scientists said 56% of the ice sheet had melted, but temperatures were compared to the 2012 heatwave. Last July 2019, a staggering 217 billion tons of meltwater flowed off of Greenland's ice sheet into the Atlantic Ocean. The melting happened after the heatwave affected Europe, setting temperature records in France and Greenland.
In August 2019, Greenland's ice sheet experienced its biggest melt of the summer, losing 11 billion tons of surface ice to the ocean in just one day. This is equivalent to 4.4 million Olympic swimming pools. CNN, an American news-based pay television channel owned by AT&T's WarnerMedia, reported that this season's ice melt has already contributed around half a millimeter to global sea levels. The massive melting of ice sheets outpaced all data collected since 1950.
Researchers Andrew Freedman and Jason Samenow explained that the melting event was sparked by the same high-pressure weather system responsible for Europe’s record-breaking July heatwave. In fact, the melting season started several weeks earlier than unusual. Greenland’s mild, dry winter and spring exacerbated the effects of the prolonged heatwave, which failed to balance out melting ice with fresh snowfall.
"The melt area has also been a lot bigger when the warm air mass from Europe arrived, but it has been a long period of warm and dry weather since May and following a dry winter so it's a little extra push rather than the main cause of the very high ice loss we've observed," Ruth Mottram, a climate scientist with the Danish Meteorological Institute, said.
Additionally, a study published in the journal Advances in Atmospheric Sciences reported that the ocean temperature in 2018 was 0.075 degrees Celsius above the 1981-2010 average. According to the researchers, the heat absorbed today by the world's oceans is now equivalent to dropping roughly five Hiroshima bombs into them every second over the past 25 years.
New Threat to Greenland’s Glacier
For years, scientists have warned us that higher global temperatures could result in more melting of Greenland’s ice sheet. They have provided us with concrete and comprehensive data showing the acceleration of melting since 2000. However, a new study published in the journal Nature Geoscience presented us with another threat to the region’s ice sheet: warm ocean water moving underneath the glaciers.
According to Digital Journal, a Canadian Internet news service that blends professional contributions with user-submitted content, the scientists studied one of the many "ice tongues,” strips of ice that floats on the water extending out from the glacier on land, of the Nioghalvfjerdsfjorden Glacier. They discovered that the ice tongue of a large glacier in King Frederick VIII Land in northeastern Greenland experienced a dramatic loss and thickness over the past 20 years. This is because it has been melting not only on the surface but also from below.
"The reason for the intensified melting is now clear," Janin Schaffer, an oceanographer from the Alfred Wegener Institute in Germany who led the team of researchers, said.
To gather data, the team used bathymetry data in measuring water temperatures near the ocean floor. The findings showed that there’s an existing underwater current more than a mile wide where warm water from the Atlantic Ocean can flow directly towards the glacier. This brings huge amounts of heat into contact with the ice and accelerates the glacier’s melting. Aside from that, the researchers found a similar current flowing near another of Greenland's glaciers, where a large ice tongue had recently broken off into the ocean.
“The readings indicate that here, too, a bathymetric sill near the seafloor accelerates warm water toward the glacier. Apparently, the intensive melting on the underside of the ice at several sites throughout Greenland is largely produced by the form of the seafloor,” Schaffer said.