What to know about the rapid melting of the Greenland ice sheet, a significant contributor to rising sea levels

An unusual warming pattern has caused the Greenland ice sheet to melt at "unusual," potentially record-breaking rates, causing it to dump even more water into the already-rising ocean, experts told ABC News.

The weather has been so warm -- up to 59 degrees Fahrenheit above the mean in some areas -- that 2 billion tons of the ice sheet melted on just June 13, according to Polar Portal, a website run by the Danish Meteorological Institute, which monitors the ice and climate in the arctic based on scientific models.

In addition, the warming season began about a month earlier than usual, DMI announced last month.

Warming events are becoming 'more and more frequent'

The warm temperatures on June 13 and 14 resulted from a pocket of air that led to clear skies and persisted for a long period of time over the eastern portion of Greenland, said Marco Tedesco, a polar scientist specializing in Greenland for the Lamont-Doherty Earth Observatory at Columbia University in New York.

The clear skies created more solar radiation, which heated the ice sheet and promoted the melting, Tedesco told ABC News.

Scientists are noticing that these events are becoming "more and more frequent," Tedesco said. Researchers believe it is connected to the jet stream, or polar vortex, becoming less stable, which creates high-pressure systems that can be sustained for longer periods of time and leads to the "exceptional melting," Tedesco said.

Last week, the temperatures were "very warm," even for summer, which hasn't yet started in the region, said Martin Stendel, senior climate and arctic researcher for the Danish Meteorological Institute.

About 40% to 45% of the ice sheet was melting on the hottest days, a new record for that time period, Tedesco said.

The ice sheet is the largest contributor of water into the ocean every year

A study published in the Proceedings of the National Academy of Sciences in April found that the melting of the Greenland ice sheet has contributed to more than a half-inch of rising ocean waters since 1972, making it the largest contributor of new water into the ocean every year.

The warming has accelerated so much in recent years that about a quarter inch of the additional water occurred in the last eight years, the study found.

On average, the Greenland ice sheet produces about 270 gigatons of discharge in the oceans per year, Tedesco said. Since 2003, the ice sheet has contributed about 10 millimeters over the last 15 years, and scientists expect that number to increase as the earth continues to warm, which would equate to about a 1 meter sea rise by the end of the century, Stendel said.

The warming temperatures also melted sea ice

About 40% of Greenland experienced "unusual" melting as a result of the unseasonably warm temperatures, which included a considerable amount of sea ice, according to DMI.

A photo taken by Danish Meteorological Institute climate scientist Steffen Olsen on June 13 shows dogs running across the sea ice in northwest Greenland, the surface of which had melted, making it appear as if they were running on water.

The water remained on top due to the rapid melt and few cracks in the ice, so there was nowhere for it to go, Stendel said.

The sea ice is more than a meter thick, which made it "perfectly safe" for the researchers to cross, he added.

A similar trend occurred in 2012

The warming season in 2012 set the record for the amount of melting in the ice sheet, according to experts. That year, melting reached more than 90 percent of the ice sheet and continued past the typical peak of high pressure from July through August, Tedesco said.

In 2012, the high-pressure system also began in April, which promoted more solar radiation and triggered a melt at the beginning of the season, Tedesco said.

The Greenland ice sheet contributed about twice the amount of water into the ocean that year, Tedesco said. While the record for the largest-ever melting was set that year, there is a possibility that 2019 could beat it, Stendel said.

It would take thousands of years for the ice sheet to recover

The ice sheet formed from thousands of years of snow layers accumulating on top of each other, Tedesco said. The weight of the top layer of snow would cause the snow below to begin expelling air, compressing the ice and making it denser.

Not only does that process take thousands of years, but it requires that the snow deposits do not melt in the warming season, Tedesco said.

The amount of snowfall during the winter can affect how fast or slow the ice melts

An abundance of snowfall during the winter months not only adds to the mass of the ice sheet, but also makes it brighter, which reflects the sun more and acts as a "blanket" for the ice, Tedesco said. This can slow down the melting in the warming season.

However, if the snow goes through multiple melting and freezing cycles, such as what happened in the past week, it transforms into "metamorphous snow," which tends to absorb more solar energy and causes the ice to melt sooner, Tedesco said.

This past winter did not see a lot of snowfall, according to Tedesco.

Sea levels rising can have catastrophic consequences

The rapidly rising sea levels are important to note, not only in terms of the next century but perhaps in the next decade or two, Tedesco said.

The sea levels surrounding New York City have been rising at around 3 millimeters per year, Tedesco said.

For example, if someone were to stand in the Hudson River in New York City where the water barely covered his or her feet in 1871, that same area of water would now come up past knee-level, Tedesco said.

Scientists expect the rising sea levels to exacerbate weather events such as storm surge, tides, rain and precipitation, Tedesco said.

One thing people should be especially aware of is the permafrost located in the northern arctic regions, particularly Canada and Siberia, that is trapping greenhouses gases, Stendel said. If temperatures rise more than 10 degrees in the arctic, the permafrost will become unstable and could release the greenhouse gases.

While this may not affect the frequency of strong storms, such as hurricanes, each individual storm could become stronger because warm air can carry more water vapor than cold air, Stendel said.

In addition, people should expect more of what is already occurring -- wet regions will get more wet, and dry regions will become drier, Stendel said.

Since a large portion of world's population live near coastlines, this could -- and already has -- lead to deaths and billions of dollars in damage, Tedesco said.