East Greenland’s retreating glaciers expose plant remains dating back to the 16th and 17th centuries

The mosses and willow shrubs found buried beneath the modern retreating glaciers of East Greenland can be dated back 400-500 years, suggesting that this period (the beginning of the Little Ice Age) was as warm or warmer than today.

It is widely accepted that Greenland’s surface temperature was a few degrees warmer, and that the volume and area of ice has been much smaller for almost all of the last 8,000-10,000 years.

What may not yet be widely accepted is the conclusion that today’s temperatures and ice extent are still in the “cold stage” range of the Holocene rather than the warm stage.

A new study documents a warmer early and middle Holocene in East Greenland than today, a time when ice caps were “absent” or much less extensive than they are now. Plant remains buried under retreating glaciers in East Greenland confirm that these places were not covered by glaciers until 400-500 years ago.

But the authors also report that there were occasional short “cold spells” during the Holocene when the extent of Greenland’s glaciers reached today’s levels.

“…The Renland glacial cap briefly reached dimensions during cold phases that may have been similar to those of today.

This suggests that today’s temperatures and ice volumes also fall within the “cold phase” range.

Brief conclusions of the study:

Holocene glacial history of the Renland Ice Cap, East Greenland, reconstructed from lake sediments

Highlights.

– Glacier-fed lake sediments limit the Holocene history of the Renland Ice Cap.
– By ∼10,000 B.C. the ice area was the same or less than it is today.
– Glacial fluctuations on a millennial scale occurred throughout the Holocene.
– To fully understand changes in glacial cover in the region, several geographic conditions must be examined.

Shrinking glaciers, melting permafrost, and shrinking sea ice indicate that the Arctic cryosphere is rapidly shrinking in response to contemporary climate warming, and this trend is expected to continue, if not accelerate.

The response of the Arctic cryosphere to past periods of climate change can provide insight into its current and future behavior. Here we examine the ∼12,000-year history of glacier and meltwater fluctuations associated with the Renland Ice Cap, East Greenland, which extends from the thermal optimum of the early Holocene through the cooling of the Little Ice Age to the present.

Precipitation from glacier-fed lakes indicates rapid Early Holocene deglaciation, with ice area likely to have been somewhat less than the present by ∼9500 B.C. Glacial activity led to periodic deposition of rock crumbs in the studied lakes during the Early Holocene, at least until ∼7500 B.C.

Stone chips are absent for most of the ∼7000-4000 BC period, suggesting that the extent of the glaciers was generally smaller than at present.

However, thin layers of bluish-gray clay throughout this period may indicate millennia of glacial expansion, with the Renland glacial cap briefly reaching a size during cold phases that may have been similar to modern times.

Glacial deposition occurred again in the late Holocene at ∼3200-3400 BP, followed by a brief glacial episode at ∼1340 BP, and then a major event starting soon after ∼1050 BP.

We hypothesize that the deposition of stone chips in the lakes in the past millennium corresponded to the advance of the Renland glaciers to their Little Ice Age positions, marked by a fresh, gray demolition boundary.

Radiocarbon dates of in situ plant remains near the current ice cap indicate a short relatively warm period of ∼500 years ago, when the ice was within the 2011 boundary, after which the glaciers recovered.

The overall pattern of ice fluctuations at Renland is similar to that at other ice caps in the region, but also has important differences, including the persistence of a possible Middle Holocene record at times when ice caps at lower elevations in the Scoresby Sound region may have been absent.

This finding supports the concept that several geographic and geomorphologic conditions must be examined to fully understand ice variations in the region.

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