The Little Ice Age was among the coldest periods of the previous 10,000 years, a period of cooling that was particularly noticable in the North Atlantic area. This cold spell, whose exact timeline scholars debate, but which seems to have actually set in around 600 years ago, was accountable for crop failures, famines, and pandemics throughout Europe, resulting in torment and death for millions. To date, the mechanisms that led to this harsh environment state have actually remained undetermined. A new paper released just recently in Science Advances gives an up-to-date picture of the events that brought about the Little Ice Age. Surprisingly, the cooling appears to have been activated by an abnormally warm episode.
When lead author Francois Lapointe, postdoctoral scientist and lecturer in geosciences at UMass Amherst and Raymond Bradley, recognized professor in geosciences at UMass Amherst began thoroughly analyzing their 3,000-year reconstruction of North Atlantic sea surface temperature levels, results of which were published in the Proceedings of the National Academy of Sciences in 2020, they discovered something surprising: a sudden change from hot conditions in the late 1300s to unprecedented cold conditions in the early 1400s, just 20 years later.
Using lots of in-depth marine records, Lapointe and Bradley discovered that there was an unusually strong northward transfer of warm water in the late 1300s which peaked around 1380. As an outcome, the waters south of Greenland and the Nordic Seas ended up being much warmer than usual. “No one has actually recognized this previously,” keeps in mind Lapointe.
Stars numbered 1 to 15 signify place of websites. Credit: Image from Lapointe et.
Normally, there is constantly a transfer of warm water from the tropics to the arctic. Its a well-known process called the Atlantic Meridional Overturning Circulation (AMOC), which resembles a planetary conveyor belt. Typically, warm water from the tropics streams north along the coast of Northern Europe, and when it reaches greater latitudes and meets colder arctic waters, it loses heat and becomes denser, causing the water to sink at the bottom of the ocean. This deep-water development then flows south along the coast of North America and continues to distribute around the globe.
In the late 1300s, AMOC reinforced considerably, which suggested that far more warm water than typical was moving north, which in turn cause rapid Arctic ice loss. Throughout a couple of decades in the late 1300s and 1400s, vast quantities of ice were eliminated into the North Atlantic, which not only cooled the North Atlantic waters, however likewise diluted their saltiness, ultimately triggering AMOC to collapse. It is this collapse that then triggered a substantial cooling.
Fast-forward to our own time: in between the 1980s and 1960s, we have actually likewise seen a fast fortifying of AMOC, which has actually been connected with persistently high pressure in the environment over Greenland. Lapointe and Bradley think the same climatic scenario took place just prior to the Little Ice Age– however what could have triggered that consistent high-pressure event in the 1380s?
The answer, Lapointe discovered, is to be found in trees. When the researchers compared their findings to a brand-new record of solar activity revealed by radiocarbon isotopes preserved in tree rings, they discovered that abnormally high solar activity was tape-recorded in the late 1300s. Such solar activity tends to lead to high air pressure over Greenland.
At the same time, less volcanic eruptions were taking place in the world, which implies that there was less ash in the air. A “cleaner” atmosphere meant that the planet was more responsive to modifications in solar output. “Hence the impact of high solar activity on the climatic blood circulation in the North-Atlantic was especially strong,” stated Lapointe.
Lapointe and Bradley have actually been wondering whether such an abrupt cooling occasion might take place again in our age of global environment change. They keep in mind that there is now much less arctic sea ice due to global warming, so an occasion like that in the early 1400s, including sea ice transportation, is unlikely. “However, we do have to keep an eye on the accumulation of freshwater in the Beaufort Sea (north of Alaska) which has increased by 40% in the past twenty years. Its export to the subpolar North Atlantic might have a strong effect on oceanic blood circulation,” stated Lapointe. “Also, relentless periods of high pressure over Greenland in summertime have actually been far more regular over the previous decade and are linked with record-breaking ice melt. Environment models do not catch these events dependably therefore we may be undervaluing future ice loss from the ice sheet, with more freshwater entering the North Atlantic, potentially causing a weakening or collapse of the AMOC.” The authors conclude that there is an immediate requirement to address these unpredictabilities.
Reference: “Little Ice Age suddenly set off by invasion of Atlantic waters into the Nordic Seas” by Francois Lapointe and Raymond S. Bradley, 15 December 2021, Science Advances.DOI: 10.1126/ sciadv.abi8230.
This research was supported by moneying from the National Science Foundation.
The Little Ice Age was one of the coldest durations of the previous 10,000 years, a period of cooling that was especially noticable in the North Atlantic area. A new paper published just recently in Science Advances provides an updated picture of the occasions that brought about the Little Ice Age. In the late 1300s, AMOC reinforced significantly, which implied that far more warm water than typical was moving north, which in turn cause rapid Arctic ice loss. Over the course of a few decades in the late 1300s and 1400s, vast amounts of ice were flushed out into the North Atlantic, which not only cooled the North Atlantic waters, however also diluted their saltiness, eventually causing AMOC to collapse. They note that there is now much less arctic sea ice due to worldwide warming, so an event like that in the early 1400s, involving sea ice transportation, is not likely.
Cold period, lasting from early 15th to mid-19th centuries, activated by abnormally warm conditions.
New research from the University of Massachusetts Amherst provides a novel response to one of the relentless concerns in historical meteorology, environmental history, and the earth sciences: what triggered the Little Ice Age? The answer, we now understand, is a paradox: warming.
