Tag Archives: geology

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Arctic is warmer than in 40,000 years

FOR IMMEDIATE RELEASE Average summer temperatures in the Canadian Arctic are now at the highest they’ve been for approaching 50,000 years, new evidence suggests. LONDON, 24 October – Good news for Arctic mosses, if not for any other Arctic creatures: little tundra plants that have been buried under the Canadian ice can feel the sunlight for the first time in at least 44,000 years. The implication is that the Arctic is now, and has been for the last 100 years, warmer than at any time in the last 44,000 years and perhaps for the last 120,000 years. This also means that the Arctic is warmer now than it was in what geologists call the early Holocene, the end of the last Ice Age – when the peak summer sunlight was roughly nine per cent greater than it is today, according to Gifford Miller of the University of Colorado Boulder, in the US. The mosses studied by Dr Miller, of course, could feel nothing: they were dead. But they could tell a story, all the same. The Arctic ice cap has been in constant retreat for the last century, and glaciers almost everywhere have been melting: there are fears that the process has begun to accelerate as greenhouse gases concentrate in the atmosphere. But as the ice recedes, it exposes evidence of the past, preserved over the millennia in the natural deep freeze.

Creating a timeline of climate change

The researchers used a technique called radiocarbon dating to establish that the mosses had been screened from the elements for at least 44,000 to 51,000 years. Since radiocarbon dating is only accurate for about 50,000 years, the mosses could have been buried for perhaps 120,000 years, since the last “interglacial” when the polar regions experienced a natural thaw. Miller and colleagues report in Geophysical Research Letters that they did their fieldwork on Baffin Island in the Arctic Circle, and measured the radiocarbon ages of the dead mosses in at least four different locations. They were careful to pick their 145 samples within one metre of the receding ice cap. Since the ice is receding at two or three metres a year, they could be sure the plant tissues had just been exposed that season. Since the plants could only have taken root in sunlight, they were evidence that the exposed terrain was once free of ice. They became silent witnesses, telling researchers about the changes through time in the frozen North. “The key piece here is just how unprecedented the warming of Arctic Canada is. This study really says the warming we are seeing is outside any kind of known natural variability, and it has to be due to increased greenhouse gases in the atmosphere,” said Miller.

Recent decades critical

Since radiocarbon clocks can only tick for so long, the Colorado team used ice cores to provide clues to the climate history of Baffin Island: each winter’s snowfall and summer melt is preserved in the icepack and like the growth rings in a tree provides a calendar of annual change. The last time temperatures on Baffin Island were as high as today was about 120,000 years ago. About 5,000 years ago, after a mellow period in the early Holocene, the Arctic began to cool again, and stayed cool until the beginning of the last century. “Although the Arctic has been warming since about 1900, the most significant warming in the region didn’t really start until the 1970s,” said Dr Miller. “And it really is in the last 20 years that the warming signal from that region has been just stunning. All of Baffin Island is melting, and we expect all of the ice caps to disappear, even if there is no additional warming.” – Climate News Network

FOR IMMEDIATE RELEASE Average summer temperatures in the Canadian Arctic are now at the highest they’ve been for approaching 50,000 years, new evidence suggests. LONDON, 24 October – Good news for Arctic mosses, if not for any other Arctic creatures: little tundra plants that have been buried under the Canadian ice can feel the sunlight for the first time in at least 44,000 years. The implication is that the Arctic is now, and has been for the last 100 years, warmer than at any time in the last 44,000 years and perhaps for the last 120,000 years. This also means that the Arctic is warmer now than it was in what geologists call the early Holocene, the end of the last Ice Age – when the peak summer sunlight was roughly nine per cent greater than it is today, according to Gifford Miller of the University of Colorado Boulder, in the US. The mosses studied by Dr Miller, of course, could feel nothing: they were dead. But they could tell a story, all the same. The Arctic ice cap has been in constant retreat for the last century, and glaciers almost everywhere have been melting: there are fears that the process has begun to accelerate as greenhouse gases concentrate in the atmosphere. But as the ice recedes, it exposes evidence of the past, preserved over the millennia in the natural deep freeze.

Creating a timeline of climate change

The researchers used a technique called radiocarbon dating to establish that the mosses had been screened from the elements for at least 44,000 to 51,000 years. Since radiocarbon dating is only accurate for about 50,000 years, the mosses could have been buried for perhaps 120,000 years, since the last “interglacial” when the polar regions experienced a natural thaw. Miller and colleagues report in Geophysical Research Letters that they did their fieldwork on Baffin Island in the Arctic Circle, and measured the radiocarbon ages of the dead mosses in at least four different locations. They were careful to pick their 145 samples within one metre of the receding ice cap. Since the ice is receding at two or three metres a year, they could be sure the plant tissues had just been exposed that season. Since the plants could only have taken root in sunlight, they were evidence that the exposed terrain was once free of ice. They became silent witnesses, telling researchers about the changes through time in the frozen North. “The key piece here is just how unprecedented the warming of Arctic Canada is. This study really says the warming we are seeing is outside any kind of known natural variability, and it has to be due to increased greenhouse gases in the atmosphere,” said Miller.

Recent decades critical

Since radiocarbon clocks can only tick for so long, the Colorado team used ice cores to provide clues to the climate history of Baffin Island: each winter’s snowfall and summer melt is preserved in the icepack and like the growth rings in a tree provides a calendar of annual change. The last time temperatures on Baffin Island were as high as today was about 120,000 years ago. About 5,000 years ago, after a mellow period in the early Holocene, the Arctic began to cool again, and stayed cool until the beginning of the last century. “Although the Arctic has been warming since about 1900, the most significant warming in the region didn’t really start until the 1970s,” said Dr Miller. “And it really is in the last 20 years that the warming signal from that region has been just stunning. All of Baffin Island is melting, and we expect all of the ice caps to disappear, even if there is no additional warming.” – Climate News Network

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Desert yields clues to species’ survival

FOR IMMEDIATE RELEASE Research into one of the world’s oldest and driest deserts has unearthed evidence of the evolutionary timeline for species that have avoided extinction by adapting to dramatic climate change LONDON, June 26 − Biodiversity’s response to global warming is difficult to predict, but new research shows that species in the distant past have adapted to, and colonised, new and increasingly arid desert zones during a period of dramatic change. The less encouraging finding from the University of Chile scientists who have studied geological evidence from the Atacama-Sechura desert region − one of the Earth’s oldest and driest deserts − is that this adaptation takes about six million years. Any wildlife response to dramatic climate change – and the kind predicted in the worst case scenario for the 21st century is certainly in the dramatic category − depends on a very large number of factors.

Barriers to movement

These include how fast plants or small animals can move to cooler zones south or north; what barriers – such as mountain ranges, lakes, cities, motorways or farms − there might be to movement; and, of course, whether the ecosystem that supports any particular species can move at the same rate. Researchers have repeatedly warned of mass extinction under conditions of climate change, but it has been much harder to calculate the rates at which species might adapt or evolve, and populations recover, in new habitats. However, there are lessons to be learned from the recent geological past − long before Homo sapiens began to create extra difficulties for the rest of creation. Climate scientists can date changes in global temperatures with reasonable accuracy, palaeontologists can identify and date fossils of characteristic climate zone species with some precision, and geneticists can measure the rate at which DNA has evolved to adapt to new environments. This last technique now delivers a good measure of evolutionary timelines. Pablo Guerrero and fellow researchers at the University of Chile’s Department of Ecological Sciences report in the Proceedings of the National Academy of Sciences that they used geological evidence to put dates to the rainfall history of the ancient Atacama-Sechura desert region of Chile and Peru and the DNA readings to measure the rates at which three different kinds of plant and one genus of lizard evolved to colonise the new habitat.

Huge time lags

They found that these groups of plants and animals made their homes in the desert only in the last 10 million years – a good 20 million years after the onset of aridity in the region. There were also huge lags – from 4 million to 14 million years − between the time these creatures moved into the desert region and when they colonised the hyper-arid places. These ultra-dry parts of the region developed about 8 million years ago, but the most diverse of the plant group moved in only two million years ago. “Similar evolutionary lag times may occur in other organisms and habitats, but these results are important in suggesting that many lineages may require very long time scales to adapt to modern desertification and climate change,” the scientists in Chile report. − Climate News Network        

FOR IMMEDIATE RELEASE Research into one of the world’s oldest and driest deserts has unearthed evidence of the evolutionary timeline for species that have avoided extinction by adapting to dramatic climate change LONDON, June 26 − Biodiversity’s response to global warming is difficult to predict, but new research shows that species in the distant past have adapted to, and colonised, new and increasingly arid desert zones during a period of dramatic change. The less encouraging finding from the University of Chile scientists who have studied geological evidence from the Atacama-Sechura desert region − one of the Earth’s oldest and driest deserts − is that this adaptation takes about six million years. Any wildlife response to dramatic climate change – and the kind predicted in the worst case scenario for the 21st century is certainly in the dramatic category − depends on a very large number of factors.

Barriers to movement

These include how fast plants or small animals can move to cooler zones south or north; what barriers – such as mountain ranges, lakes, cities, motorways or farms − there might be to movement; and, of course, whether the ecosystem that supports any particular species can move at the same rate. Researchers have repeatedly warned of mass extinction under conditions of climate change, but it has been much harder to calculate the rates at which species might adapt or evolve, and populations recover, in new habitats. However, there are lessons to be learned from the recent geological past − long before Homo sapiens began to create extra difficulties for the rest of creation. Climate scientists can date changes in global temperatures with reasonable accuracy, palaeontologists can identify and date fossils of characteristic climate zone species with some precision, and geneticists can measure the rate at which DNA has evolved to adapt to new environments. This last technique now delivers a good measure of evolutionary timelines. Pablo Guerrero and fellow researchers at the University of Chile’s Department of Ecological Sciences report in the Proceedings of the National Academy of Sciences that they used geological evidence to put dates to the rainfall history of the ancient Atacama-Sechura desert region of Chile and Peru and the DNA readings to measure the rates at which three different kinds of plant and one genus of lizard evolved to colonise the new habitat.

Huge time lags

They found that these groups of plants and animals made their homes in the desert only in the last 10 million years – a good 20 million years after the onset of aridity in the region. There were also huge lags – from 4 million to 14 million years − between the time these creatures moved into the desert region and when they colonised the hyper-arid places. These ultra-dry parts of the region developed about 8 million years ago, but the most diverse of the plant group moved in only two million years ago. “Similar evolutionary lag times may occur in other organisms and habitats, but these results are important in suggesting that many lineages may require very long time scales to adapt to modern desertification and climate change,” the scientists in Chile report. − Climate News Network