Before their disappearance at the end of the Pleistocene, North American mastodons trekked hundreds of miles across the continent, altering their range in response to dramatic climatic shifts, according to research published Tuesday in Nature Communications.

In a largest-of-its-kind survey of mastodon mitochondrial genomes, using DNA collected from 33 individual animals, researchers were able to retrace the movements of ancient mastodon populations.

"We used one genetic marker known as the full mitochondrial genome," Hendrik Poinar, evolutionary geneticist and director of the Ancient DNA Center at McMaster University in Canada, told UPI in an email. "This is a maternally inherited marker that does not recombine and allows us to trace migration history and female population size through time."

"We compared the mitochondrial genomes from all mastodons to say something about where they fall in relation to each other," Poinar said. "When combined with their geographical location you can make sense of migrational direction."

The genomic data showed mastodons from farther north featured lower levels of genetic diversity, suggesting smaller subsets of southern populations migrated north.

By comparing differences in the number of genetic mutations between individual mastodons and geographically distinct groups of mastodons, researchers were able to better understand the relationships between different population subsets. They also were able to estimate when different branches of the family tree split off and migrated elsewhere.

When researchers compared the timing of mastodon migrations with paleoclimate evidence, they were able to confirm that groups of mastodons headed north as temperature rose and glaciers receded.

"The interglacial occupation of mastodons has been proposed for a few years now, but I think we show the strongest evidence of it," lead study author Emil Karpinski, graduate student at the Ancient DNA Center, told UPI.

Scientists have previously suggested North American mastodons were hunted to extinction by people of the Clovis culture, a prehistoric Paleoamerican culture that spread across the continent some 13,000 years ago. But the latest research suggests climate change likely played a role in the mastodon's disappearance.

"[The findings] certainly suggest that the mastodons migrated huge distances over the course of generations, tracking environments that favored their ecology, but ultimately that they were susceptible to changing climate, perhaps priming them for human predation," Poinar said.

The researchers say their findings have implications for modern conservation science. Today, a variety of animal species, including elk and bears, are expanding their ranges northward as a result of anthropogenic greening.

"If these northern populations show the same pattern as mastodons, they might also be very similar genetically and the loss of populations in the southern ranges may have detrimental effects for the genetic health of the species," Karpinski said.

Earth's ice sheets tracking worst-case climate scenarios
Paris (AFP) Sept 1, 2020 - The Greenland and Antarctic ice sheets, which hold enough frozen water to lift oceans 65 metres, are tracking the UN's worst-case scenarios for sea level rise, researchers have said, highlighting flaws in current climate change models.

Mass loss caused by melt-water and crumbling ice from 2007 to 2017 aligned with the most extreme forecasts from the Intergovernmental Panel for Climate Change (IPCC), which see the two ice sheets adding up to 40 centimetres (nearly 16 inches) to global oceans by 2100, they reported on Monday in Nature Climate Change.

Such an increase would have a devastating impact worldwide, increasing the destructive power of storm surges and exposing coastal regions home to hundreds of millions of people to repeated and severe flooding.

That is nearly three times more than mid-range projections from the IPCC's last major Assessment Report in 2014, which predicted a 70 centimetre rise in sea level from all sources, including mountain glaciers and the expansion of ocean water as it warms.

Despite this clear mismatch between the observed reality of accelerating ice sheet disintegration and the models tracking those trends, a special IPCC report last year on the planet's frozen regions maintained the same end-of-century projections for Greenland, and allowed for only a small increase from Antarctica under the highest greenhouse gas emissions scenario.

"We need to come up with a new worst-case scenario for the ice sheets because they are already melting at a rate in line with our current one," lead author Thomas Slater, a researcher at the Centre for Polar Observation and Modelling at the University of Leeds, told AFP.

"Sea level projections are critical in helping governments plan climate policy, mitigation and adaptation strategies.

"If we underestimate future sea level rise, then these measures may be inadequate and leave coastal communities vulnerable."

Ice sheet losses at the upper end of the IPCC forecasts would by itself expose some 50 million people to annual coastal flooding worldwide by mid-century, according to research published last year.

- Balance upended -

Several factors explain why the climate models underlying UN projections for sea level might have given short shrift to ice sheets, according to the new analysis.

Ice sheet models do well in describing the long-term impact of gradual global warming, which has seen temperatures at the poles rise far more quickly than for the planet as a whole.

But they have failed to account for short-term fluctuations in weather patterns that are, themselves, deeply influenced by climate change.

"For Greenland, much of the ice loss is now being driven by surface melt events during hot summers -- processes not captured in the AR5 simulations," said Slater, referring to the 2014 IPCC report, the fifth since 1992.

"We need to understand these better to improve our sea level rise predictions."

Until the turn of the 21st century, the West Antarctic and Greenland ice sheets generally accumulated as much mass as they shed. Runoff, in other words, was compensated by fresh snowfall.

But over the last two decades, the gathering pace of global warming has upended this balance.

Last year, Greenland lost a record 532 billion tonnes of ice -- the equivalent of six Olympic pools of cold, fresh water flowing into the Atlantic every second. This run-off accounted for 40 percent of sea level rise in 2019.

"We have now had record breaking ice loss twice in less than 10 years," said Twila Moon, a research scientist at the University of Colorado, noting that the previous melts on this scale were 150 and 600 years ago.

"If everyone's alarm bells were not already ringing, they must be now."

A new generation of climate models that better reflects how ice sheets, the oceans and the atmosphere interact will underpin the IPCC's next major report, which will be completed next year, said Slater.

In another study published earlier this month in The Cryosphere, a journal of the European Geosciences Union, Slater and colleagues calculated that Earth's ice masses -- including mountain glaciers, the Arctic ice cap, and both ice sheets -- lost nearly 28 trillion tonnes of mass between 1994 and 2017.

Less than half of that amount contributed to sea level rise. The Arctic ice cap, for example, forms in the ocean, and thus does not increase sea level when it melts.

The rate of ice loss, they found, has increased nearly 60 percent of that time period.

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Global survey using NASA data shows dramatic growth of glacial lakes
Washington DC (SPX) Sep 01, 2020
In the largest-ever study of glacial lakes, researchers using 30 years of NASA satellite data have found that the volume of these lakes worldwide has increased by about 50% since 1990 as glaciers melt and retreat due to climate change. The findings, published in the journal Nature Climate Change, will aid researchers assessing the potential hazards to communities downstream of these often unstable lakes and help improve the accuracy of sea level rise estimates by advancing our understanding of how ... read more