Historic Ice Retreats
Can you imagine one ice chunk as big as Hawaii disappearing instantaneously from its ice sheet? This happened in the Arctic Ocean’s Storfjorden Through about 11,000 years back.
According to Tine L. Rasmussen, CAGE first author and also a professor, measures the dramatic ice disappearance in Storfjorden Through matches what was observed in Greenland and Antarctica. Although an unnatural phenomenon, there are weekly studies showing that ice sheets typically retreat up to between two and four km per year, but that’s speeding up already.
The last time there was a deglaciation was about 20,000 – 10,000 years ago. This was a time when global warming coexisted with ice sheets shrinking fast. However, matching possible correlations with today’s studies requires more than simple semantics. The period here had unstable climates, and refreezing and new ice formations affected big melts. As a result, deriving the speed of this ice retreat with respect to climate changes proves difficult.
Rasmussen also comments that they have studied the development of ice sheets between 20,000 and 10,000 years ago via the cores of marine sediments. These 12 cores were collected in the same area for the last 18 years, followed by a meticulous analysis of several microfossils of foraminifera, a single-celled life form.
Fossils of the foraminifera contain elements that help to reshape the large amount of available information regarding how the environment was during prehistoric times. The sediments picked weed out in slices each one representing a time period of between 30 and 70 years. Notably, over 70 of such samples were analysed, following the dating. .
According to Rasmussen, the result was that ice sheets had started retreating about 20,000 years ago, but have been lingering on the fjord ridges. After 15000 year back when the ocean temperature and atmosphere warmed up, affecting ocean circulation. At that time also, a large chunk of ice sheets went missing. Again, when the Holocene period of warmth came, things picked up speed. Ever since, researchers had not seen more evidence of ice sheets over the ocean floor.
Also, periods of rapid retreats of ice sheets consistently correlate with ocean’s global warming. This is supported by retreats of ice sheets from the eight fjord system of Northern Norwegian.
Rasmussen adds that the reports strengthen the hypothesis that increases in global warming and ocean temperature are the direct players in the chain of events causing dramatic and rapid disintegration of ice sheets.
That said, it is easy to see the alarming implication it has on the present day. The historic melt from the glacier, the Holocene took 10,000. With the current climate change, this will be way more rapid, such as we can already see in Antarctica.