Rapid glacial advance reconstructed during the time of Norse occupation in
Boulder, Colo., USA: The Greenland Ice Sheet is the second largest ice body
in the world, and it has the potential to contribute significantly to
global sea-level rise in a warming global climate. Understanding the
long-term record of the Greenland Ice Sheet, including both records of
glacial advance and retreat, is critical in validating approaches that
model future ice-sheet scenarios. However, this reconstruction can be
extremely challenging. A new study published yesterday in the journal Geology reconstructed the advance of one of the largest tidewater
glaciers in Greenland to provide a better understanding of long-term
“In the news, we’re very used to hearing about glacial retreat, and that’s
because in a warming climate scenario—which is what we’re in at the
moment—we generally document ice masses retreating. However, we also want
to understand how glaciers react if there is a climate cooling and
subsequent advance. To do this, we need to reconstruct glacier geometry
from the past,” said Danni Pearce, co-lead author of the study.
An interdisciplinary team of researchers studied the advance of Kangiata
Nunaata Sermia (KNS)—the largest tidewater glacier in southwest
Greenland—during a period of cooling when the Norse had settlements in
Greenland. Differing from glaciers that are strictly on land, tidewater
glaciers extend and flow all the way to the ocean or a sea, where they can
then calve and break up into icebergs.
Reconstructing the advance of glaciers can be exceptionally difficult,
because the glacier typically destroys or reworks everything in its path as
it advances forward. The research team undertook multiple field seasons in
Greenland, traveling on foot to remote sites—many of which hadn’t been
visited since the 1930s—to try and uncover the record of KNS advance.
“When we went out into the field, we had absolutely no idea whether the
evidence would be there or not, so I was incredibly nervous. Though we did
a huge amount of planning beforehand, until you go out into the field you
don’t know what you’re going to find,” said James Lea, the other co-lead
author of the study.
By traveling on foot, the research team was able to more closely examine
and explore sites that otherwise may have been missed if traveling by
helicopter. The team’s planning paid off, and the sedimentary sequences
they studied and sampled held the clues they were looking for to date and
track the advance of the glacier.
The research team found that during the twelfth and thirteenth centuries
CE, KNS advanced at least 15 km, at a rate of ~115 m/yr. This rate of
advance is comparable to modern rates of glacial retreat observed over the
past ~200 years, indicating that when climate is cooler glaciers can
advance equally as fast as they are currently retreating. The glacier
reached its maximum extent by 1761 CE during the Little Ice Age,
culminating in a total advance of ~20 km. Since then, KNS has retreated ~23
km to its present position.
The period when the glacier was advancing coincided with when the Norse
were present in Greenland. Prior to its maximum extent during the Little
Ice Age, the researchers found that KNS advanced to a location within only
5 km of a Norse farmstead.
“Even though KNS was rapidly coming down the fjord, it did not seem to
affect the Norse, which we found really unusual,” said Pearce. “So the team
started to think about the surrounding environment and the amount of
iceberg production in the fjord during that time. At the moment, the fjord
is completely filled with icebergs, making boat access challenging, and we
know from historical record that it has been like this for the last 200
years while the glacier has been retreating. However, for KNS to advance at
115 m/yr, it needed to hang onto its ice and could not have been producing
a lot of icebergs. So we actually think that the fjord would have looked
very different with few icebergs, which allowed the Norse far more easy
access to this site for farming, hunting, and fishing.”
In the 1930s, archaeologists who visited the site hypothesized that
conditions in the fjord must have been different from the present day in
order for the Norse to have occupied the site, and this current research
study provides data to support these long-held ideas.
“So we have this counterintuitive notion that climate cooling and glacier
advance might have actually helped the Norse in this specific circumstance
and allowed them to navigate more of the fjord more easily,” said Lea.
The Norse left Greenland during the fifteenth century CE, and these results
are consistent with the idea that a cooling climate was likely not the
cause of their exodus; rather, a combination of economic factors likely led
the Norse to abandon Greenland.
The results from this research reconstructing rapid glacial advance are
also shown to be consistent with the ways ice sheet models work, which
brings confidence to the projections from these models. Having accurate
models and projections are crucial in understanding and preparing for
future scenarios of continued retreat of the Greenland Ice Sheet and
associated sea-level rise.
“Melt from Greenland not only impacts sea-level change but also the ecology
around the ice sheets, fisheries, the biological productivity of the
oceans—how much algae is growing. And also because the types of glaciers
we’re looking at produce icebergs these can cause hazards to shipping and
trade, especially if the Northwest Passage opens up as it is expected to,”
said James Lea.
Pearce added, “Our research shows that climate cooling can change iceberg
calving behavior and drive glacier advance at rates just as rapid as
current retreat. It also shows how resilient the Greenlandic Norse were to
the changing environmental conditions. Such adaptation can give us hope for
the changes we may face over the coming century.’’
Greenland Glacier Change Viewer:
Greenland tidewater glacier advanced rapidly during era of Norse
Danni M. Pearce*, James M. Lea*, Douglas W.F. Mair, Brice R. Rea, J. Edward
Schofield, Nicholas A. Kamenos, Kathryn M. Schoenrock, Lukasz Stachnik,
Bonnie Lewis, Lestyn Barr, and Ruth Mottram
Contact: Danni M. Pearce, firstname.lastname@example.org; James M.
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