Greenland ice may exaggerate magnitude of 13,000-year-old deep freeze

Ice samples pulled from nearly a mile below the surface of Greenland glaciers have long served as a historical thermometer, adding temperature data to studies of the local conditions up to the Northern Hemisphere’s climate.

But the method — comparing the ratio of oxygen isotopes buried as snow fell over millennia — may not be such a straightforward indicator of air temperature.

“We don’t believe the ice cores can be interpreted purely as a signal of temperature,” says Anders Carlson, a University of Wisconsin-Madison geosciences professor. “You have to consider where the precipitation that formed the ice came from.”

According to a study published today by the Proceedings of the National Academy of Sciences, the Greenland ice core drifts notably from other records of Northern Hemisphere temperatures during the Younger Dryas, a period beginning nearly 13,000 years ago of cooling so abrupt it’s believed to be unmatched since.

Such periods of speedy cooling and warming are of special interest to climate scientists, who are teasing out the mechanisms of high-speed change to better understand and predict the changes occurring in our own time.

In the case of the Younger Dryas, average temperatures — based on the Greenland ice — plummeted as much as 15 degrees Celsius in a few centuries, and then shot back up nearly as much (over just decades) about 1,000 years later.

“In terms of temperature during the Younger Dryas, the only thing that looks like Greenland ice cores are Greenland ice cores,” Carlson says. “They are supposed to be iconic for the Northern Hemisphere, but we have four other records that do not agree with the Greenland ice cores for that time. That abrupt cooling is there, just not to the same degree.”

Working with UW-Madison climatologist Zhengyu Liu, collaborators at the National Center for Atmospheric Research and others, Carlson found their computer climate model breaking down on the Younger Dryas.

While it could reliably recreate temperatures in the Oldest Dryas — a similar cooling period about 18,000 years ago — they just couldn’t find a lever in the model that would simulate a Younger Dryas that matched the Greenland ice cores.

“You can totally turn off ocean circulation, have Arctic sea ice advance all the way across the North Atlantic, and you still will have a warmer climate during the Younger Dryas than the Oldest Dryas because of the carbon dioxide,” Carlson say.

By the time the Younger Dryas rolled around, there was more carbon dioxide in the air — about 50 parts per million more. The warming effects of that much CO2 overwhelmed the rest of the conditions that make the Oldest and Younger Dryas so alike, and demonstrates a heightened sensitivity for Arctic temperatures to rising greenhouse gases in the atmosphere.

The researchers zeroed in on the Northern Hemisphere’s temperature outlier, Greenland ice cores, and found that the conversion of oxygen isotope ratio to temperature typically used on the ice cores did not account for the sort of crash climate change occurring during the Younger Dryas. It assumes prevailing winds and jet streams and storm tracks are providing the moisture for Greenland precipitation from the Atlantic Ocean.

“The Laurentide ice sheet, which covered much of North America down into the northern United States, is getting smaller as the Younger Dryas approaches,” Carlson says. “That’s like taking out a mountain of ice three kilometers high. As that melts, it allows more Pacific Ocean moisture to cross the continent and hit the Greenland ice sheet.”

The two oceans have distinctly different ratios of oxygen isotopes, allowing for a different isotope ratio where the water falls as snow.

“We ran an oxygen isotope-enabled atmosphere model, so we could simulate what these ice cores are actually recording, and it can match the actual oxygen isotopes in the ice core even though the temperature doesn’t cool as much,” Carlson says. “That, to us, means the source of precipitation has changed in Greenland across the last deglatiation. And therefore that the strict interpretation of this iconic record as purely temperature of snowfall above this ice sheet is wrong.”

By the study’s findings, Greenland temperatures may not have cooled as significantly as climate headed into the Younger Dryas relative to the Oldest Dryas, because of the rise in atmospheric carbon dioxide that had occurred since the Oldest Dryas.

“You can say at the end of the Younger Dryas it warmed 10, plus or minus five, degrees Celsius. But what happened on this pathway into the event, you can’t see,” Carlson says.

It’s a fresh reminder from an ancient ice core that climate science is full of nuance, according to Carlson.

“Abrupt climate changes have happened, but they come with complex shifts in the way climate inputs like moisture moved around,” he says. “You can’t take one difference and interpret it solely as changes in temperature, and that’s what we’re seeing here in the Greenland ice cores.”

Greenland ice may exaggerate magnitude of 13,000-year-old deep freeze

Ice samples pulled from nearly a mile below the surface of Greenland glaciers have long served as a historical thermometer, adding temperature data to studies of the local conditions up to the Northern Hemisphere’s climate.

But the method — comparing the ratio of oxygen isotopes buried as snow fell over millennia — may not be such a straightforward indicator of air temperature.

“We don’t believe the ice cores can be interpreted purely as a signal of temperature,” says Anders Carlson, a University of Wisconsin-Madison geosciences professor. “You have to consider where the precipitation that formed the ice came from.”

According to a study published today by the Proceedings of the National Academy of Sciences, the Greenland ice core drifts notably from other records of Northern Hemisphere temperatures during the Younger Dryas, a period beginning nearly 13,000 years ago of cooling so abrupt it’s believed to be unmatched since.

Such periods of speedy cooling and warming are of special interest to climate scientists, who are teasing out the mechanisms of high-speed change to better understand and predict the changes occurring in our own time.

In the case of the Younger Dryas, average temperatures — based on the Greenland ice — plummeted as much as 15 degrees Celsius in a few centuries, and then shot back up nearly as much (over just decades) about 1,000 years later.

“In terms of temperature during the Younger Dryas, the only thing that looks like Greenland ice cores are Greenland ice cores,” Carlson says. “They are supposed to be iconic for the Northern Hemisphere, but we have four other records that do not agree with the Greenland ice cores for that time. That abrupt cooling is there, just not to the same degree.”

Working with UW-Madison climatologist Zhengyu Liu, collaborators at the National Center for Atmospheric Research and others, Carlson found their computer climate model breaking down on the Younger Dryas.

While it could reliably recreate temperatures in the Oldest Dryas — a similar cooling period about 18,000 years ago — they just couldn’t find a lever in the model that would simulate a Younger Dryas that matched the Greenland ice cores.

“You can totally turn off ocean circulation, have Arctic sea ice advance all the way across the North Atlantic, and you still will have a warmer climate during the Younger Dryas than the Oldest Dryas because of the carbon dioxide,” Carlson say.

By the time the Younger Dryas rolled around, there was more carbon dioxide in the air — about 50 parts per million more. The warming effects of that much CO2 overwhelmed the rest of the conditions that make the Oldest and Younger Dryas so alike, and demonstrates a heightened sensitivity for Arctic temperatures to rising greenhouse gases in the atmosphere.

The researchers zeroed in on the Northern Hemisphere’s temperature outlier, Greenland ice cores, and found that the conversion of oxygen isotope ratio to temperature typically used on the ice cores did not account for the sort of crash climate change occurring during the Younger Dryas. It assumes prevailing winds and jet streams and storm tracks are providing the moisture for Greenland precipitation from the Atlantic Ocean.

“The Laurentide ice sheet, which covered much of North America down into the northern United States, is getting smaller as the Younger Dryas approaches,” Carlson says. “That’s like taking out a mountain of ice three kilometers high. As that melts, it allows more Pacific Ocean moisture to cross the continent and hit the Greenland ice sheet.”

The two oceans have distinctly different ratios of oxygen isotopes, allowing for a different isotope ratio where the water falls as snow.

“We ran an oxygen isotope-enabled atmosphere model, so we could simulate what these ice cores are actually recording, and it can match the actual oxygen isotopes in the ice core even though the temperature doesn’t cool as much,” Carlson says. “That, to us, means the source of precipitation has changed in Greenland across the last deglatiation. And therefore that the strict interpretation of this iconic record as purely temperature of snowfall above this ice sheet is wrong.”

By the study’s findings, Greenland temperatures may not have cooled as significantly as climate headed into the Younger Dryas relative to the Oldest Dryas, because of the rise in atmospheric carbon dioxide that had occurred since the Oldest Dryas.

“You can say at the end of the Younger Dryas it warmed 10, plus or minus five, degrees Celsius. But what happened on this pathway into the event, you can’t see,” Carlson says.

It’s a fresh reminder from an ancient ice core that climate science is full of nuance, according to Carlson.

“Abrupt climate changes have happened, but they come with complex shifts in the way climate inputs like moisture moved around,” he says. “You can’t take one difference and interpret it solely as changes in temperature, and that’s what we’re seeing here in the Greenland ice cores.”

Mercury mineral evolution

Mineral evolution posits that Earth’s near-surface mineral diversity gradually increased through an array of chemical and biological processes. A dozen different species in interstellar dust particles that formed the solar system have evolved to more than 4500 species today. Previous work from Carnegie’s Bob Hazen demonstrated that up to two thirds of the known types of minerals on Earth can be directly or indirectly linked to biological activity. Now Hazen has turned his focus specifically on minerals containing the element mercury and their evolution on our planet as a result of geological and biological activity. His work, published in American Mineralogist, demonstrates that the creation of most minerals containing mercury is fundamentally linked to several episodes of supercontinent assembly over the last 3 billion years.

Mineral evolution is an approach to understanding Earth’s changing near-surface geochemistry. All chemical elements were present from the start of our Solar System, but at first they formed comparatively few minerals–perhaps no more than 500 different species in the first billion years. As time passed on the planet, novel combinations of elements led to new minerals. Although as much as 50% of the mercury that contributed to Earth’s accretion was lost to volatile chemical processing, 4.5 billion years of mineral evolution has led to at least 90 different mercury-containing minerals now found on Earth.

Hazen and his team examined the first-documented appearances of these 90 different mercury-containing minerals on Earth. They were able to correlate much of this new mineral creation with episodes of supercontinent formation–periods when most of Earth’s dry land converged into single landmasses. They found that of the 60 mercury-containing minerals that first appeared on Earth between 2.8 billion and 65 million years ago, 50 were created during three periods of supercontinent assembly. Their analysis suggests that the evolution of new mercury-containing minerals followed periods of continental collision and mineralization associated with mountain formation.

By contrast, far fewer types of mercury-containing minerals formed during periods when these supercontinents were stable, or when they were breaking apart. And in one striking exception to this trend, the billion-year-long interval that included the assembly of the Rodinian supercontinent (approximately 1.8 to 0.8 billion years ago) saw no mercury mineralization anywhere on Earth. Hazen and his colleagues speculate that this hiatus could have been due to a sulfide-rich ocean, which quickly reacted with any available mercury and thus prevented mercury from interacting chemically with other elements.

The role of biology is also critical in understanding the mineral evolution of mercury. Although mercury is rarely directly involved in biological processes–except in some rare bacteria–its interactions with oxygen came about entirely due to the appearance of the photosynthetic process, which plants and certain bacteria use to convert sunlight into chemical energy. Mercury also has a strong affinity for carbon-based compounds that come from biological material, such as coal, shale, petroleum, and natural gas products.

“Our work shows that in the case of mercury, evolution seems to have been driven by hydrothermal activity associated with continents colliding and forming mountain ranges, as well as by the drastic increase in oxygen caused by the rise of life on Earth,” Hazen said. “Future work will have to correlate specific mineral occurrences to specific tectonic events.”

Future work will also focus on the minerals of other elements to see how they differ and correlate with mercury’s mineral evolution, and to new strategies for locating as yet undiscovered deposits of critical resources.

“It’s important to keep honing in on the ways that minerals have evolved on our planet from their simple elemental origins to the vast array in existence today,” Hazen said.

Mercury mineral evolution

Mineral evolution posits that Earth’s near-surface mineral diversity gradually increased through an array of chemical and biological processes. A dozen different species in interstellar dust particles that formed the solar system have evolved to more than 4500 species today. Previous work from Carnegie’s Bob Hazen demonstrated that up to two thirds of the known types of minerals on Earth can be directly or indirectly linked to biological activity. Now Hazen has turned his focus specifically on minerals containing the element mercury and their evolution on our planet as a result of geological and biological activity. His work, published in American Mineralogist, demonstrates that the creation of most minerals containing mercury is fundamentally linked to several episodes of supercontinent assembly over the last 3 billion years.

Mineral evolution is an approach to understanding Earth’s changing near-surface geochemistry. All chemical elements were present from the start of our Solar System, but at first they formed comparatively few minerals–perhaps no more than 500 different species in the first billion years. As time passed on the planet, novel combinations of elements led to new minerals. Although as much as 50% of the mercury that contributed to Earth’s accretion was lost to volatile chemical processing, 4.5 billion years of mineral evolution has led to at least 90 different mercury-containing minerals now found on Earth.

Hazen and his team examined the first-documented appearances of these 90 different mercury-containing minerals on Earth. They were able to correlate much of this new mineral creation with episodes of supercontinent formation–periods when most of Earth’s dry land converged into single landmasses. They found that of the 60 mercury-containing minerals that first appeared on Earth between 2.8 billion and 65 million years ago, 50 were created during three periods of supercontinent assembly. Their analysis suggests that the evolution of new mercury-containing minerals followed periods of continental collision and mineralization associated with mountain formation.

By contrast, far fewer types of mercury-containing minerals formed during periods when these supercontinents were stable, or when they were breaking apart. And in one striking exception to this trend, the billion-year-long interval that included the assembly of the Rodinian supercontinent (approximately 1.8 to 0.8 billion years ago) saw no mercury mineralization anywhere on Earth. Hazen and his colleagues speculate that this hiatus could have been due to a sulfide-rich ocean, which quickly reacted with any available mercury and thus prevented mercury from interacting chemically with other elements.

The role of biology is also critical in understanding the mineral evolution of mercury. Although mercury is rarely directly involved in biological processes–except in some rare bacteria–its interactions with oxygen came about entirely due to the appearance of the photosynthetic process, which plants and certain bacteria use to convert sunlight into chemical energy. Mercury also has a strong affinity for carbon-based compounds that come from biological material, such as coal, shale, petroleum, and natural gas products.

“Our work shows that in the case of mercury, evolution seems to have been driven by hydrothermal activity associated with continents colliding and forming mountain ranges, as well as by the drastic increase in oxygen caused by the rise of life on Earth,” Hazen said. “Future work will have to correlate specific mineral occurrences to specific tectonic events.”

Future work will also focus on the minerals of other elements to see how they differ and correlate with mercury’s mineral evolution, and to new strategies for locating as yet undiscovered deposits of critical resources.

“It’s important to keep honing in on the ways that minerals have evolved on our planet from their simple elemental origins to the vast array in existence today,” Hazen said.

Elephant seals help uncover slower-than-expected Antarctic melting

Don’t let the hobbling, wobbling, and blubber fool you into thinking elephant
seals are merely sluggish sun bathers. In fact, scientists are benefiting from these seals’
surprisingly lengthy migrations to determine critical information about Antarctic melting and
future sea level rise.

A team of scientists have drilled holes through an Antarctic ice shelf, the Fimbul Ice Shelf, to
gather the first direct measurements regarding melting of the shelf’s underside. A group of
elephant seals, outfitted with sensors that measure salinity, temperature, and depth sensors added
fundamental information to the scientists’ data set, which led the researchers to conclude that
parts of eastern Antarctica are melting at significantly lower rates than current models predict.

“It has been unclear, until now, how much warm deep water rises below the Fimbul Ice shelf,
and previous ocean models, focusing on the circulation below the Fimbul Ice Shelf, have
predicted temperatures and melt rates that are too high, suggesting a significant mass loss in this
region that is actually not taking place as fast as previously thought,” said lead author of the
study and PhD student at the Norwegian Polar Institute (NPI), Tore Hattermann.

The Fimbul Ice Shelf – located along eastern Antarctica in the Weddell Sea – is the sixth largest
of the forty-three ice shelves that dapple Antarctica’s perimeter. Both its size and proximity to
the Eastern Antarctic Ice Sheet – the largest ice sheet on Earth, which if it melted, could lead to
extreme changes in sea level – have made the Fimbul Ice Shelf an attractive object of study.

The team is the first to provide direct, observational evidence that the Fimbul Ice Shelf is melting
from underneath by three, equally important processes. Their results confirm a 20-year-old
theory about how ice shelves melt that, until now, was too complex to be further investigated
with models that had no direct observations for comparison. These processes likely apply to
other areas of Antarctica, primarily the eastern half because of its similar water and wind
circulation patterns, Hattermann said.

The scientists report their findings on June 22 in the journal Geophysical Research Letters, a
publication of the American Geophysical Union.

Using nearly 12 tons of equipment, the scientists drilled three holes of an average depth of 230
meters (820 feet) that were dispersed approximately 50-100 kilometers (31-62 miles) apart along
the shelf, which spans an area roughly twice the size of New Jersey. The location of each hole
was strategically chosen so that the various pathways by which water moves beneath the ice
shelf could be observed.

What the team observed was that during the summer, relatively warm surface waters are pushed
beneath the ice shelves by strong wind-driven currents. While this happens, another process
transports warm water deeper in the ocean towards the coast and below the ice.

Combining with those effects is a process inherent to the cold ocean waters: The freezing point
of water depends on its depth. The deeper the water, the lower its freezing point. Water of a
constant temperature will freeze on the surface but remain liquid (or melt, if it was already
frozen) at a given depth, like at the bottom of an ice shelf. Therefore, there is a slight but
continuous melting of the Fimbul Ice Shelf’s undersides due to this physical phenomenon.

To understand the extent to which these three processes interact and melt the ice shelf, scientists
needed a detailed record of annual water cycles and circulation around eastern Antarctica. Enter
nine male elephant seals that swam 1,600 kilometers (about 1,000 miles) from Bouvet Island
(written as Bouvetoya in Norwegian), in the middle of the Southern Ocean, to the outskirts of the
Fimbul Ice Shelf.

Hattermann and his team borrowed the “seal data” from biologists of the Norwegian Polar
Institute, who originally gathered the data during their Marine Mammal Exploration of the
Oceans Pole to Pole (MEOP) research project, part of the International Polar Year program.

“Nobody was expecting that the MEOP seals from Bouvetoya would swim straight to the
Antarctic and stay along the Fimbul Ice Shelf for the entire winter,” Hattermann said. “But, this
behavior certainly provided an impressive and unique data set.”

For nine consecutive months, the sensors atop the seals’ heads read the temperature and salinity
of the waters along the outskirts of the Fimbul Ice Shelf and recorded their changes over time. To
collect the same amount of continuous data from a ship would not only incur far greater cost but
would be almost impossible during the winter months due to dangerous ice buildup.

From the “seal data”, the scientists accumulated enough knowledge concerning the area’s water
circulation and how it changes over the seasons to construct the most complete picture of what
and how the Fimbul Ice Shelf is melting from the bottom up.

It turns out that past studies, which were based on computer models without any direct data for
comparison or guidance, overestimate the water temperatures and extent of melting beneath the
Fimbul Ice Shelf. This has led to the misconception, Hattermann said, that the ice shelf is losing
mass at a faster rate than it is gaining mass, leading to an overall loss of mass. The model results
were in contrast to the available data from satellite observations, which are supported by the new
measurements.

The team’s results show that water temperatures are far lower than computer models predicted,
which means that the Fimbul Ice Shelf is melting at a slower rate. Perhaps indicating that the
shelf is neither losing nor gaining mass at the moment because ice buildup from snowfall has
kept up with the rate of mass loss, Hattermann said.

“Our data shows what needs to be included in the next generation models, in order to be able to
do a good job in predicting future melt rates,” Hattermann said.

Because wind patterns and water cycles are similar for large parts of eastern Antarctica,
Hattermann said, his team’s results could help predict the next time when a section of the Fimbul
Ice Shelf, or other ice shelves along the eastern coast of Antarctica, may break off. Because ice
shelves are already submerged, their melting does not directly influence sea level rise. However,
the rate that ice shelves are melting is still crucial to this issue, he said.

“Ice shelves act as a mechanical barrier for the grounded inland ice that continuously moves
from higher elevation towards the coast,” Hattermann said. “Once an ice shelf is removed, this
ice flow may speed up, which then increases the loss of grounded ice, causing the sea level rise.”

Elephant seals help uncover slower-than-expected Antarctic melting

Don’t let the hobbling, wobbling, and blubber fool you into thinking elephant
seals are merely sluggish sun bathers. In fact, scientists are benefiting from these seals’
surprisingly lengthy migrations to determine critical information about Antarctic melting and
future sea level rise.

A team of scientists have drilled holes through an Antarctic ice shelf, the Fimbul Ice Shelf, to
gather the first direct measurements regarding melting of the shelf’s underside. A group of
elephant seals, outfitted with sensors that measure salinity, temperature, and depth sensors added
fundamental information to the scientists’ data set, which led the researchers to conclude that
parts of eastern Antarctica are melting at significantly lower rates than current models predict.

“It has been unclear, until now, how much warm deep water rises below the Fimbul Ice shelf,
and previous ocean models, focusing on the circulation below the Fimbul Ice Shelf, have
predicted temperatures and melt rates that are too high, suggesting a significant mass loss in this
region that is actually not taking place as fast as previously thought,” said lead author of the
study and PhD student at the Norwegian Polar Institute (NPI), Tore Hattermann.

The Fimbul Ice Shelf – located along eastern Antarctica in the Weddell Sea – is the sixth largest
of the forty-three ice shelves that dapple Antarctica’s perimeter. Both its size and proximity to
the Eastern Antarctic Ice Sheet – the largest ice sheet on Earth, which if it melted, could lead to
extreme changes in sea level – have made the Fimbul Ice Shelf an attractive object of study.

The team is the first to provide direct, observational evidence that the Fimbul Ice Shelf is melting
from underneath by three, equally important processes. Their results confirm a 20-year-old
theory about how ice shelves melt that, until now, was too complex to be further investigated
with models that had no direct observations for comparison. These processes likely apply to
other areas of Antarctica, primarily the eastern half because of its similar water and wind
circulation patterns, Hattermann said.

The scientists report their findings on June 22 in the journal Geophysical Research Letters, a
publication of the American Geophysical Union.

Using nearly 12 tons of equipment, the scientists drilled three holes of an average depth of 230
meters (820 feet) that were dispersed approximately 50-100 kilometers (31-62 miles) apart along
the shelf, which spans an area roughly twice the size of New Jersey. The location of each hole
was strategically chosen so that the various pathways by which water moves beneath the ice
shelf could be observed.

What the team observed was that during the summer, relatively warm surface waters are pushed
beneath the ice shelves by strong wind-driven currents. While this happens, another process
transports warm water deeper in the ocean towards the coast and below the ice.

Combining with those effects is a process inherent to the cold ocean waters: The freezing point
of water depends on its depth. The deeper the water, the lower its freezing point. Water of a
constant temperature will freeze on the surface but remain liquid (or melt, if it was already
frozen) at a given depth, like at the bottom of an ice shelf. Therefore, there is a slight but
continuous melting of the Fimbul Ice Shelf’s undersides due to this physical phenomenon.

To understand the extent to which these three processes interact and melt the ice shelf, scientists
needed a detailed record of annual water cycles and circulation around eastern Antarctica. Enter
nine male elephant seals that swam 1,600 kilometers (about 1,000 miles) from Bouvet Island
(written as Bouvetoya in Norwegian), in the middle of the Southern Ocean, to the outskirts of the
Fimbul Ice Shelf.

Hattermann and his team borrowed the “seal data” from biologists of the Norwegian Polar
Institute, who originally gathered the data during their Marine Mammal Exploration of the
Oceans Pole to Pole (MEOP) research project, part of the International Polar Year program.

“Nobody was expecting that the MEOP seals from Bouvetoya would swim straight to the
Antarctic and stay along the Fimbul Ice Shelf for the entire winter,” Hattermann said. “But, this
behavior certainly provided an impressive and unique data set.”

For nine consecutive months, the sensors atop the seals’ heads read the temperature and salinity
of the waters along the outskirts of the Fimbul Ice Shelf and recorded their changes over time. To
collect the same amount of continuous data from a ship would not only incur far greater cost but
would be almost impossible during the winter months due to dangerous ice buildup.

From the “seal data”, the scientists accumulated enough knowledge concerning the area’s water
circulation and how it changes over the seasons to construct the most complete picture of what
and how the Fimbul Ice Shelf is melting from the bottom up.

It turns out that past studies, which were based on computer models without any direct data for
comparison or guidance, overestimate the water temperatures and extent of melting beneath the
Fimbul Ice Shelf. This has led to the misconception, Hattermann said, that the ice shelf is losing
mass at a faster rate than it is gaining mass, leading to an overall loss of mass. The model results
were in contrast to the available data from satellite observations, which are supported by the new
measurements.

The team’s results show that water temperatures are far lower than computer models predicted,
which means that the Fimbul Ice Shelf is melting at a slower rate. Perhaps indicating that the
shelf is neither losing nor gaining mass at the moment because ice buildup from snowfall has
kept up with the rate of mass loss, Hattermann said.

“Our data shows what needs to be included in the next generation models, in order to be able to
do a good job in predicting future melt rates,” Hattermann said.

Because wind patterns and water cycles are similar for large parts of eastern Antarctica,
Hattermann said, his team’s results could help predict the next time when a section of the Fimbul
Ice Shelf, or other ice shelves along the eastern coast of Antarctica, may break off. Because ice
shelves are already submerged, their melting does not directly influence sea level rise. However,
the rate that ice shelves are melting is still crucial to this issue, he said.

“Ice shelves act as a mechanical barrier for the grounded inland ice that continuously moves
from higher elevation towards the coast,” Hattermann said. “Once an ice shelf is removed, this
ice flow may speed up, which then increases the loss of grounded ice, causing the sea level rise.”

New deglaciation data opens door for earlier First Americans migration

A new study of lake sediment cores from Sanak Island in the western Gulf of Alaska suggests that deglaciation there from the last Ice Age took place as much as 1,500 to 2,000 years earlier than previously thought, opening the door for earlier coastal migration models for the Americas.

The Sanak Island Biocomplexity Project, funded by the National Science Foundation, also concluded that the maximum thickness of the ice sheet in the Sanak Island region during the last glacial maximum was 70 meters – or about half that previously projected – suggesting that deglaciation could have happened more rapidly than earlier models predicted.

Results of the study were just published in the professional journal, Quaternary Science Reviews.


The study, led by Nicole Misarti of Oregon State University, is important because it suggests that the possible coastal migration of people from Asia into North America and South America – popularly known as “First Americans” studies – could have begun as much as two millennia earlier than the generally accepted date of ice retreat in this area, which was 15,000 years before present.

Well-established archaeology sites at Monte Verde, Chile, and Huaca Prieta, Peru, date back 14,000 to 14,200 years ago, giving little time for expansion if humans had not come to the Americas until 15,000 years before present – as many models suggest.

The massive ice sheets that covered this part of the Earth during the last Ice Age would have prevented widespread migration into the Americas, most archaeologists believe.

“It is important to note that we did not find any archaeological evidence documenting earlier entrance into the continent,” said Misarti, a post-doctoral researcher in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences. “But we did collect cores from widespread places on the island and determined the lake’s age of origin based on 22 radiocarbon dates that clearly document that the retreat of the Alaska Peninsula Glacier Complex was earlier than previously thought.”

“Glaciers would have retreated sufficiently so as to not hinder the movement of humans along the southern edge of the Bering land bridge as early as almost 17,000 years ago,” added Misarti, who recently accepted a faculty position at the University of Alaska at Fairbanks.

Interestingly, the study began as a way to examine the abundance of ancient salmon runs in the region. As the researchers began examining core samples from Sanak Island lakes looking for evidence of salmon remains, however, they began getting radiocarbon dates much earlier than they had expected. These dates were based on the organic material in the sediments, which was from terrestrial plant macrofossils indicating the region was ice-free earlier than believed.

The researchers were surprised to find the lakes ranged in age from 16,500 to 17,000 years ago.

A third factor influencing the find came from pollen, Misarti said.

“We found a full contingent of pollen that indicated dry tundra vegetation by 16,300 years ago,” she said. “That would have been a viable landscape for people to survive on, or move through. It wasn’t just bare ice and rock.”

The Sanak Island site is remote, about 700 miles from Anchorage, Alaska, and about 40 miles from the coast of the western Alaska Peninsula, where the ice sheets may have been thicker and longer lasting, Misarti pointed out. “The region wasn’t one big glacial complex,” she said. “The ice was thinner and the glaciers retreated earlier.”

Other studies have shown that warmer sea surface temperatures may have preceded the early retreat of the Alaska Peninsula Glacier Complex (APGC), which may have supported productive coastal ecosystems.

Wrote the researchers in their article: “While not proving that first Americans migrated along this corridor, these latest data from Sanak Island show that human migration across this portion of the coastal landscape was unimpeded by the APGC after 17 (thousand years before present), with a viable terrestrial landscape in place by 16.3 (thousand years before present), well before the earliest accepted sites in the Americas were inhabited.”

New deglaciation data opens door for earlier First Americans migration

A new study of lake sediment cores from Sanak Island in the western Gulf of Alaska suggests that deglaciation there from the last Ice Age took place as much as 1,500 to 2,000 years earlier than previously thought, opening the door for earlier coastal migration models for the Americas.

The Sanak Island Biocomplexity Project, funded by the National Science Foundation, also concluded that the maximum thickness of the ice sheet in the Sanak Island region during the last glacial maximum was 70 meters – or about half that previously projected – suggesting that deglaciation could have happened more rapidly than earlier models predicted.

Results of the study were just published in the professional journal, Quaternary Science Reviews.


The study, led by Nicole Misarti of Oregon State University, is important because it suggests that the possible coastal migration of people from Asia into North America and South America – popularly known as “First Americans” studies – could have begun as much as two millennia earlier than the generally accepted date of ice retreat in this area, which was 15,000 years before present.

Well-established archaeology sites at Monte Verde, Chile, and Huaca Prieta, Peru, date back 14,000 to 14,200 years ago, giving little time for expansion if humans had not come to the Americas until 15,000 years before present – as many models suggest.

The massive ice sheets that covered this part of the Earth during the last Ice Age would have prevented widespread migration into the Americas, most archaeologists believe.

“It is important to note that we did not find any archaeological evidence documenting earlier entrance into the continent,” said Misarti, a post-doctoral researcher in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences. “But we did collect cores from widespread places on the island and determined the lake’s age of origin based on 22 radiocarbon dates that clearly document that the retreat of the Alaska Peninsula Glacier Complex was earlier than previously thought.”

“Glaciers would have retreated sufficiently so as to not hinder the movement of humans along the southern edge of the Bering land bridge as early as almost 17,000 years ago,” added Misarti, who recently accepted a faculty position at the University of Alaska at Fairbanks.

Interestingly, the study began as a way to examine the abundance of ancient salmon runs in the region. As the researchers began examining core samples from Sanak Island lakes looking for evidence of salmon remains, however, they began getting radiocarbon dates much earlier than they had expected. These dates were based on the organic material in the sediments, which was from terrestrial plant macrofossils indicating the region was ice-free earlier than believed.

The researchers were surprised to find the lakes ranged in age from 16,500 to 17,000 years ago.

A third factor influencing the find came from pollen, Misarti said.

“We found a full contingent of pollen that indicated dry tundra vegetation by 16,300 years ago,” she said. “That would have been a viable landscape for people to survive on, or move through. It wasn’t just bare ice and rock.”

The Sanak Island site is remote, about 700 miles from Anchorage, Alaska, and about 40 miles from the coast of the western Alaska Peninsula, where the ice sheets may have been thicker and longer lasting, Misarti pointed out. “The region wasn’t one big glacial complex,” she said. “The ice was thinner and the glaciers retreated earlier.”

Other studies have shown that warmer sea surface temperatures may have preceded the early retreat of the Alaska Peninsula Glacier Complex (APGC), which may have supported productive coastal ecosystems.

Wrote the researchers in their article: “While not proving that first Americans migrated along this corridor, these latest data from Sanak Island show that human migration across this portion of the coastal landscape was unimpeded by the APGC after 17 (thousand years before present), with a viable terrestrial landscape in place by 16.3 (thousand years before present), well before the earliest accepted sites in the Americas were inhabited.”

Silicon strip detectors look for the heaviest element

Silicon alpha-particle detectors developed and built at the Institute of Electron Technology (ITE) in Warsaw, Poland, in cooperation with the Institut für Radiochemie – Technische Universität München (IR TUM) in Munich are currently being used in an international experiment aimed at producing and detecting atomic nuclei of the as yet undiscovered element 120. The experiment, conducted at the Centre for Heavy Ion Research (GSI Helmholtzzentrum für Schwerionenforschung GmbH) in Darmstadt, began a few weeks ago and will continue until the end of the year.

The semiconductor devices designed to detect alpha particles (as well as beta particles and protons) were developed from the ground up in Warsaw by a team of engineers from ITE, and are protected by patents. The devices earned international acclaim and are used in leading nuclear research centres, including the GSI centre in Darmstadt and the Joint Institute for Nuclear Research in Dubna. They contributed, among others, to the discovery of heavy atomic nuclei, including isotope 283 of element 112 (copernicium, Cn) in Dubna, and isotopes 270, 271 and 277 of element 108 (hassium, Hs) in Darmstadt. In 2009 they made it possible to observe a record number of thirteen nuclei of isotopes 288 and 289 of element 114 (flerovium) during a single experiment in Darmstadt. The devices played a crucial role in the experimental confirmation of the island of stability theory. The results of the experiments conducted using the ITE detectors are the subject of highly cited publications in prestigious scientific journals, including “Nature”. The research described in these publications led the International Union of Pure and Applied Chemistry and the International Union of Pure and Applied Physics to officially recognize and add to the periodic table elements 112 and 114.

“In contrast to the majority of semiconductor devices, our detectors have a very large p-n junction area, a thick electrically active area and a high radiation resistance. Many complex technical problems had to be solved in order to build devices with optimum operating parameters,” says Maciej Węgrzecki, MSc, Eng, head of the team developing silicon detectors at ITE.

Detectors from ITE are currently being used in an experiment employing the TASCA (TransActinide Separator and Chemistry Apparatus) ion separator at the Centre for Heavy Ion Research in Darmstadt. The aim of the experiment is to gain an understanding of the physical and chemical properties of elements with atomic number greater than 104, and to produce, for the first time, nuclei of the element with atomic number 120.

Alpha-particle detectors built at ITE are manufactured on silicon plates with specially crafted diffusion regions. When a particle passes through a detector, it creates electron-hole pairs in the semiconductor material, which induces electrical current. State-of-the-art detectors from ITE are double-sided: they have two parallel detecting surfaces, each covered with 16 semiconductor strips. The strips on a one surface are perpendicular to the strips on the other surface. By measuring signals from the strips on both surfaces, it is possible to accurately determine where the particle passed through the detector.

The Institute of Electron Technology supplied the 16-strip silicon detectors to the GSI centre in Darmstadt in January. At the centre they were installed in the Focal Plane Detector Box (FPDB), which forms part of the TASCA ion separator. Eight double-sided strip detectors and two single-sided 8-strip detectors were mounted on FPDB sides.

Silicon strip detectors look for the heaviest element

Silicon alpha-particle detectors developed and built at the Institute of Electron Technology (ITE) in Warsaw, Poland, in cooperation with the Institut für Radiochemie – Technische Universität München (IR TUM) in Munich are currently being used in an international experiment aimed at producing and detecting atomic nuclei of the as yet undiscovered element 120. The experiment, conducted at the Centre for Heavy Ion Research (GSI Helmholtzzentrum für Schwerionenforschung GmbH) in Darmstadt, began a few weeks ago and will continue until the end of the year.

The semiconductor devices designed to detect alpha particles (as well as beta particles and protons) were developed from the ground up in Warsaw by a team of engineers from ITE, and are protected by patents. The devices earned international acclaim and are used in leading nuclear research centres, including the GSI centre in Darmstadt and the Joint Institute for Nuclear Research in Dubna. They contributed, among others, to the discovery of heavy atomic nuclei, including isotope 283 of element 112 (copernicium, Cn) in Dubna, and isotopes 270, 271 and 277 of element 108 (hassium, Hs) in Darmstadt. In 2009 they made it possible to observe a record number of thirteen nuclei of isotopes 288 and 289 of element 114 (flerovium) during a single experiment in Darmstadt. The devices played a crucial role in the experimental confirmation of the island of stability theory. The results of the experiments conducted using the ITE detectors are the subject of highly cited publications in prestigious scientific journals, including “Nature”. The research described in these publications led the International Union of Pure and Applied Chemistry and the International Union of Pure and Applied Physics to officially recognize and add to the periodic table elements 112 and 114.

“In contrast to the majority of semiconductor devices, our detectors have a very large p-n junction area, a thick electrically active area and a high radiation resistance. Many complex technical problems had to be solved in order to build devices with optimum operating parameters,” says Maciej Węgrzecki, MSc, Eng, head of the team developing silicon detectors at ITE.

Detectors from ITE are currently being used in an experiment employing the TASCA (TransActinide Separator and Chemistry Apparatus) ion separator at the Centre for Heavy Ion Research in Darmstadt. The aim of the experiment is to gain an understanding of the physical and chemical properties of elements with atomic number greater than 104, and to produce, for the first time, nuclei of the element with atomic number 120.

Alpha-particle detectors built at ITE are manufactured on silicon plates with specially crafted diffusion regions. When a particle passes through a detector, it creates electron-hole pairs in the semiconductor material, which induces electrical current. State-of-the-art detectors from ITE are double-sided: they have two parallel detecting surfaces, each covered with 16 semiconductor strips. The strips on a one surface are perpendicular to the strips on the other surface. By measuring signals from the strips on both surfaces, it is possible to accurately determine where the particle passed through the detector.

The Institute of Electron Technology supplied the 16-strip silicon detectors to the GSI centre in Darmstadt in January. At the centre they were installed in the Focal Plane Detector Box (FPDB), which forms part of the TASCA ion separator. Eight double-sided strip detectors and two single-sided 8-strip detectors were mounted on FPDB sides.