The Greenland ice sheet lost 22 gigatonnes of ice in a single day on July 28 as a Northern Hemisphere heatwave saw temperatures reach more than double their seasonal average, Reuters reports. The quantity of water released by the melt was sufficient to submerge the entire state of Florida by 5 centimeters (2 inches).

As the heatwave continued, the Danish Meteorological Institute reported a record high temperature of 23.4°C (74.12°F) the following day at Nerlerit Inaat airport, according to AFP. Considering the average summer temperature in Greenland is only 10°C (50°F), such extreme heat has intensified fears about the stability of the Greenland ice sheet.

Second in volume only to the Antarctic ice sheet, the mass of frozen water that covers Greenland is currently melting faster than at any time in the past 12,000 years, and researchers believe it may have already crossed its tipping point, meaning there is now nothing we can do to save it.

According to a recent study, the melting of the Greenland ice sheet has caused sea levels to rise by 10.6 millimeters since 1990. Should it melt completely, worst-case scenarios could see sea levels increase by a staggering 7 meters (23 feet) around the world.

In contrast, the Antarctic ice sheet has so far only contributed 7.2 millimeters to the global rise in sea level, but has the potential to produce an increase of 58 meters (190 feet) should it melt completely.

Two years ago, extreme summer temperatures saw the Greenland ice sheet shrink to its lowest volume since observations began in 1981, with the largest single-day melting event also occurring in late July 2019. While last week’s massive melt didn’t release quite as much water as the heatwave of two summers ago, it did affect a larger area, and the ongoing effects of the soaring temperatures have resulted in an average daily melt of around 8 metric tons per day.

Aside from producing a significant rise in sea levels, the melting of the ice sheets may also result in large amounts of mercury being pumped into the ocean. Recent research has shown that the water being released by melting ice in Greenland is surprisingly rich in the toxic metal. Scientists are unsure why this is the case, with no obvious source of mercury present in Greenland, although they suspect that it may stem from natural geochemical processes.