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Climate History Rewritten: Arctic Ice an Early Arrival
June 01, 2006PROVIDENCE, R.I. — For the first time, scientists have pulled up prehistoric geologic records from the frigid vault of the Arctic Ocean. One of the findings, evidence of glacial Arctic ice from 45 million years ago, recasts a critical chapter of global climate history.
The evidence — pea-sized pebbles locked inside a 430 meter-long sediment core — shows that glaciers formed in the Arctic Ocean about 14 million years earlier than geologists had thought. This means that the immense sheets of ice at the Earth's poles formed simultaneously, something researchers call "bipolar symmetry" in one of three reports on Arctic ice highlighted on the cover of Nature.
Previously, geologists believed glaciers formed in Antarctica long before they appeared in the Arctic. The new evidence clears up this climate mystery and underscores the role that carbon dioxide and other greenhouse gases play in climate change, according to Steven Clemens, associate professor (research) in the Department of Geological Sciences at Brown University and a co-author of the Nature papers.
"In the past, scientists thought shifting tectonic plates and changes in ocean circulation patterns in the Southern Hemisphere may have prompted ice to form earlier in Antarctica," Clemens said. "But there was other data that contradicted this theory. Now much of what we know about the evolution of ice on Earth makes more sense. And the evidence underscores the importance of greenhouse gases as a driver of climate change. If you inject or remove large amounts of carbon in the atmosphere, you get truly global climate change."
Earth shifted from a "greenhouse" climate to an "icehouse" climate roughly 45 million years ago, a dramatic cooling that changed wind patterns, ocean currents and land and ocean temperatures and had a profound impact on plant and animal life. How this change played out in the Arctic, however, has never been decisively documented. That history, written in sediment on the seafloor, sits locked under thick, dense ice.
The Arctic Coring Expedition (ACEX), supported by the Integrated Ocean Drilling Program, an international marine research program, successfully penetrated sea ice up to 16 feet thick. This feat took two ice-breakers and a drill ship that hauled up sediment gathered 430 meters below the seafloor along the Lomonsov Ridge, an undersea sliver of the Eurasian continent that broke away and sunk as the Arctic Ocean opened to the Atlantic and Pacific oceans.
Clemens was a member of ACEX, led by Kathryn Moran at the University of Rhode Island and Jan Backman at Stockholm University. A paleoceanographer, Clemens was brought in to help analyze the sediment cores, which contained a stunning 54 million years of climate history. Working in a German laboratory, Clemens and other members of the science team studied the samples to determine their physical, mineralogical and biological makeup.
The team found:
- Sediment from the most recent era, stretching from the present to about 25 million years ago, was marked by clay with coarse sand. The sand, along with small pebbles, comes from continents — blown by wind or carried by icebergs that deposited these bits onto the seafloor. These samples contained plankton, clear signs of salt water.
- Sediment dating from 25 to 44 million years ago was marked by condensed silt containing no discernible signs of biological life. This era is a mystery, a hole in the historical record.
- Sediment dating back 44 to 49 million years ago contained remnants of both fresh- and salt-water algae in the clay, including a surprise — spores of Azolla, a fresh-water fern. Scientists believe that fresh water may have sat on the surface, with denser salt water sitting toward the bottom. The evidence suggests that the ocean was in transition, moving from the prehistoric "greenhouse" world to the "icehouse" world that exists today.
- Sediment from the earliest era, dating from 49 to 54 million years ago, was silty clay containing Apectodinium, microfossils that are strong markers of an abrupt warming event. This evidence suggests that Arctic was as warm as the subtropics about 55 million years ago — much warmer than previously estimated.
Clemens said the major finding — evidence of ice-deposited debris 45 million years ago — came in the form of pebbles. Why? Glaciers scrape across the land as they grow, carrying ground rock with them. When glaciers reach the sea, some of that ice shears off and forms icebergs, which shed pebbles as they melt.
This evidence of synchronous ice formation in the Arctic and Antarctic in the past may help bolster the evidence of "bipolar symmetry" today. In recent months, scientists have reported rapid melting of the worlds' ice, from the Antarctic ice sheet to Greenland glaciers. Many scientists believe the shrinking ice is linked to a sharp increase in greenhouse gases.
"Bipolar ice forms together and melts together," Clemens said. "Carbon levels are a huge driver of ice volume and global climate change, at all time scales."
The International Ocean Drilling Program supported the research. The program receives primary funding from the National Science Foundation and Japan's Ministry of Science, Education, Culture, Sports, Science and Technology. The ACEX platform operations were funded by ECORD, the European Consortium for Ocean Research Drilling, a contributing member of IODP. As an affiliate member, the People's Republic of China also supported the expedition.
Brown University
"In the past, scientists thought shifting tectonic plates and changes in ocean circulation patterns in the Southern Hemisphere may have prompted ice to form earlier in Antarctica," Clemens said. "But there was other data that contradicted this theory. Now much of what we know about the evolution of ice on Earth makes more sense. And the evidence underscores the importance of greenhouse gases as a driver of climate change. If you inject or remove large amounts of carbon in the atmosphere, you get truly global climate change."
Earth shifted from a "greenhouse" climate to an "icehouse" climate roughly 45 million years ago, a dramatic cooling that changed wind patterns, ocean currents and land and ocean temperatures and had a profound impact on plant and animal life. How this change played out in the Arctic, however, has never been decisively documented. That history, written in sediment on the seafloor, sits locked under thick, dense ice.
The Arctic Coring Expedition (ACEX), supported by the Integrated Ocean Drilling Program, an international marine research program, successfully penetrated sea ice up to 16 feet thick. This feat took two ice-breakers and a drill ship that hauled up sediment gathered 430 meters below the seafloor along the Lomonsov Ridge, an undersea sliver of the Eurasian continent that broke away and sunk as the Arctic Ocean opened to the Atlantic and Pacific oceans.
Clemens was a member of ACEX, led by Kathryn Moran at the University of Rhode Island and Jan Backman at Stockholm University. A paleoceanographer, Clemens was brought in to help analyze the sediment cores, which contained a stunning 54 million years of climate history. Working in a German laboratory, Clemens and other members of the science team studied the samples to determine their physical, mineralogical and biological makeup.
The team found:
- Sediment from the most recent era, stretching from the present to about 25 million years ago, was marked by clay with coarse sand. The sand, along with small pebbles, comes from continents — blown by wind or carried by icebergs that deposited these bits onto the seafloor. These samples contained plankton, clear signs of salt water.
- Sediment dating from 25 to 44 million years ago was marked by condensed silt containing no discernible signs of biological life. This era is a mystery, a hole in the historical record.
- Sediment dating back 44 to 49 million years ago contained remnants of both fresh- and salt-water algae in the clay, including a surprise — spores of Azolla, a fresh-water fern. Scientists believe that fresh water may have sat on the surface, with denser salt water sitting toward the bottom. The evidence suggests that the ocean was in transition, moving from the prehistoric "greenhouse" world to the "icehouse" world that exists today.
- Sediment from the earliest era, dating from 49 to 54 million years ago, was silty clay containing Apectodinium, microfossils that are strong markers of an abrupt warming event. This evidence suggests that Arctic was as warm as the subtropics about 55 million years ago — much warmer than previously estimated.
Clemens said the major finding — evidence of ice-deposited debris 45 million years ago — came in the form of pebbles. Why? Glaciers scrape across the land as they grow, carrying ground rock with them. When glaciers reach the sea, some of that ice shears off and forms icebergs, which shed pebbles as they melt.
This evidence of synchronous ice formation in the Arctic and Antarctic in the past may help bolster the evidence of "bipolar symmetry" today. In recent months, scientists have reported rapid melting of the worlds' ice, from the Antarctic ice sheet to Greenland glaciers. Many scientists believe the shrinking ice is linked to a sharp increase in greenhouse gases.
"Bipolar ice forms together and melts together," Clemens said. "Carbon levels are a huge driver of ice volume and global climate change, at all time scales."
The International Ocean Drilling Program supported the research. The program receives primary funding from the National Science Foundation and Japan's Ministry of Science, Education, Culture, Sports, Science and Technology. The ACEX platform operations were funded by ECORD, the European Consortium for Ocean Research Drilling, a contributing member of IODP. As an affiliate member, the People's Republic of China also supported the expedition.
Brown University
Arctic Ice Current Events and Arctic Ice News RSSNASA study finds rising Arctic storm activity sways sea ice, climate
A new NASA study shows that the rising frequency and intensity of arctic storms over the last half century, attributed to progressively warmer waters, directly provoked acceleration of the rate of arctic sea ice drift, long considered by scientists as a bellwether of climate change.
For toy-like NASA robots in Arctic, ice research is child's play
Several snowmobiles navigated speedily over arctic ice and snow in Alaska's outback in late June. This scene might seem ordinary except that the recently unveiled snowmobiles are unmanned, autonomous, toy-size robots called SnoMotes - the first prototype network of their kind envisioned to rove treacherous areas of the Arctic and Antarctic capturing more accurate measurements that will help scientists better understand what is causing the well-documented melting of ice in those regions.
How will the Arctic sea ice cover develop this summer?
The ice cover in the Arctic Ocean at the end of summer 2008 will lie, with almost 100 per cent probability, below that of the year 2005 - the year with the second lowest sea ice extent ever measured.
CU-Boulder researchers forecast 3-in-5 chance of record low Arctic sea ice in 2008
New University of Colorado at Boulder calculations indicate the record low minimum extent of sea ice across the Arctic last September has a three-in-five chance of being shattered again in 2008 because of continued warming temperatures and a preponderance of younger, thinner ice.
Arctic Ice More Vulnerable to Sunny Weather, New Study Shows
The shrinking expanse of Arctic sea ice is increasingly vulnerable to summer sunshine, new research concludes.
Researchers say Arctic sea ice still at risk despite cold winter
Using the latest satellite observations, NASA researchers and others report that the Arctic is still on "thin ice" when it comes to the condition of sea ice cover in the region. A colder-than-average winter in some regions of the Arctic this year has yielded an increase in the area of new sea ice, while the older sea ice that lasts for several years has continued to decline.
UNH-NOAA ocean mapping expedition yields new insights into arctic depths
New Arctic sea floor data released today by the University of New Hampshire and the National Oceanic and Atmospheric Administration suggests that the foot of the continental slope off Alaska is more than 100 nautical miles farther from the U.S. coast than previously assumed.
Older Arctic sea ice replaced by young, thin ice, says CU-Boulder study
A new study by University of Colorado at Boulder researchers indicates older, multi-year sea ice in the Arctic is giving way to younger, thinner ice, making it more susceptible to record summer sea-ice lows like the one that occurred in 2007.
Icy calculations on a hot topic
University of Utah mathematicians have arrived at a new understanding of how salt-saturated ocean water flows through sea ice - a discovery that promises to improve forecasts of how global warming will affect polar icepacks.
Explorers to Use New Robotic Vehicles to Hunt for Life and Hydrothermal Vents on Arctic Seafloor
Scientists and engineers from the Woods Hole Oceanographic Institution (WHOI) have just completed a successful test of new robotic vehicles designed for use beneath the ice of the Arctic Ocean.
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