(CN) – If history is any indication, the retreat of ice from Greenland may occur sooner than anyone expected, according to a study published Monday.
Microscopic marine fossils played a vital role for researchers in their study that sought to reconstruct the climate from the most recent ice age, some 450,000 years ago in southern Greenland. Researchers from the University of Bergen in Norway analyzed a wide timeframe of data to better understand the threshold it would take for Greenland’s ice sheet to collapse and melt away.
Located between the Arctic and Atlantic oceans, the island nation of Greenland is dominated by a 660,000 square-mile sheet of ice that covers roughly 80% of the landmass and is one of the only permanent ice sheets outside the South Pole.
Like the polar ice caps, Greenland’s ice sheet is a huge litmus test of the planet’s rising temperature. Complete melting of the Greenland ice sheet would account for a staggering 23-foot rise in global sea levels, according to researchers.
In their study published in the Proceedings of the National Academy of Sciences, researchers sought to capture a timeframe over the past 450,000 years at a site off southern Greenland. This timeframe includes four interglacial periods – periods of milder climate between two glacial periods.
Approximately 450,000 years ago marked the beginning of the Kansan glaciation or the third most recent glacial period, where ice sheets reached the height of landmass covered during the end of the Pleistocene Period.
Data gathered from microfossils allowed researchers to reconstruct the sea surface temperatures (SSTs) from their intended timeframe and this showed temperature conditions were warm or warmer than at present during all four previous interglacial periods – but not by much.
The average summer SST ranged from about 45 to 52 degrees over the last 450,000 years, with the most recent SST average around 45 degrees according to the study. The most complete deglaciation – where ice melted away from a previously glaciated area – occurred during these interglacial periods but it was only slightly warmer than the present. And ice remained on the southern end of Greenland even during the warmest periods.
During the time with the strongest ice disappearance, temperatures were higher than present levels for longer than any other time period, which might illustrate that during of warming periods influences how much land the Greenland ice sheet can cover.
Most alarmingly, the researchers found the threshold for a large retreat of the ice sheet could be just 1.8 degrees warmer than current conditions – within the range of projected averages for this century, depending on duration and magnitude of rising temperatures.
A recent study published in the journal Nature found Greenland’s ice sheet is melting so quickly that the homes of nearly 400 million people will be underwater within 80 years due to rising sea levels. The rate of loss has increased from 33 billion tons of ice lost per year in the 1990s to 254 billion tons per year in the last decade, according to the study – a seven-fold increase in less than 30 years.