Polar Oceans Key to Temperature in the Tropics

Scientists have found that the ocean temperature at Earth's polar extremes has a significant impact thousands of miles away at the equator.

Newcastle University's Dr Erin McClymont is part of an international team of researchers who have published research in Science June 18, 2010 demonstrating a close link between the changes in the subpolar climate and the development of the modern tropical Pacific climate around two million years ago.

The team believes this solves another piece of the puzzle concerning oceanic behaviour and its influence on climate.

This research, led by the Institut de Ciència i Tecnologia Ambientals in Barcelona, studied the Northern Pacific and Southern Atlantic sea-surface temperatures from the Pliocene Era (3.65 million years ago) to the present day. Data obtained during the reconstruction indicates that the regions close to the poles of both oceans have played a fundamental role in the way the tropical climate has evolved.

The cooling and expansion of polar waters between 1.8 and 1.2 million years ago increased the temperature difference between the equator and the poles. This intensified atmospheric circulation and helped to develop the modern day 'cold tongue' in the east Pacific.

Created by a shallow thermocline -- the layer of ocean water in which temperatures fall rapidly -- the cold tongue brings cold, deep waters to the surface in the east tropical Pacific. Under the warmer climate of the Pliocene, the thermocline was deeper and the cold tongue was much smaller, creating a situation more like the 'El Niño' events that hit the Pacific every three to five years.

"Our results show that the polar oceans play a key role in the global climate, and that one outcome of a rise in global temperature could be an increase in the depth of the thermocline and contraction of the cold tongue in the eastern Pacific," said Dr McClymont. "The high-latitudes are currently experiencing large climate changes, and our data show that this could impact on tropical climates as we saw in the Pliocene."

The study of Pliocene climate has been the subject of intense research as this era represents the most recent climatic period in Earth's history when average temperatures were significantly higher than today over a sustained period. As a result, the Pliocene is thought to be the closest predictor of Earth's climate in the future.

How it works: Analysing deep sea 'fossils'

Researchers analysed marine sediment collected by the international Integrated Ocean Drilling Program, which is supported in the UK by the Natural Environment Research Council (NERC). Sediment cores were drilled in water depths exceeding 3km to measure the composition of alkenones -- highly resistant organic compounds produced by phytoplankton.

The phytoplankton live in the surface ocean and change their alkenone chemistry in response to temperature changes. The researchers used these 'biomarkers' or 'chemical fossils' to reconstruct the temperatures of the surface ocean.

"These molecules are 'fossils' in the same way that shells or fish fall to the bottom of the ocean and are preserved," said Dr McClymont, who is a member of the Quaternary Research Group within Newcastle University's School of Geography, Politics and Sociology. "Molecules which remained from the phytoplankton were gradually buried beneath layers of sediment beneath the ocean floor, and by analysing these we were able to reconstruct the temperatures of the surface ocean in the past."

Reconstruction of the surface temperature in the Northern Pacific and Southern Atlantic has enabled a simultaneous sea-surface cooling to be identified in the subpolar regions of the two hemispheres in the period between 1.8 and 1.2 million years ago. This finding coincides with the formation of the equatorial Pacific cold tongue -- which currently almost disappears during any El Niño conditions.

Previous studies have shown that, during the warm conditions of the Pliocene, this cold tongue was not present, creating a situation similar to a permanent El Niño situation in the equatorial Pacific.

(i) The research is based on Dr Alfredo Martínez-García's doctoral thesis, who is currently a researcher with both the Swiss Federal Institute of Technology, ETH Zurich, and with the DFG-Leibniz Centre at the University of Postdam, Germany). The thesis was undertaken at the UAB and directed by Dr Antoni Rosell Melé, an ICTA ICREA researcher and adjunct professor with the Department of Geography. This work was carried out in collaboration with Dr Gerald H. Haug, of ETH and DFG-Leibniz Centre; Dr Erin L. McClymont of Newcastle University (UK); and Dr Rainer Gersonde, of the Alfred Wegener Institute (Germany).Newcastle University (2010, June 21). Polar oceans key to temperature in the tropics.ScienceDaily. Retrieved June 22, 2010, from http://www.sciencedaily.com/releases/2010/06/100617143934.htm

Peering Under The Ice Of Collapsing Polar Coast

Starting this month, a giant NASA DC-8 aircraft loaded with geophysical instruments and scientists will buzz at low level over the coasts of West Antarctica, where ice sheets are collapsing at a pace far beyond what scientists expected a few years ago. The flights, dubbed Operation Ice Bridge, are an effort by NASA in cooperation with university researchers to image what is happening on, and under, the ice, in order to estimate future sea-level rises that might result.

Since 2003, laser measurements of ice surfaces from NASA's ICESat satellite have shown that vast ice masses in Greenland and West Antarctica are thinning and flowing quickly seaward. Last month, a report in the journal Nature based on the satellite's measurements showed that some parts of the Antarctic area to be surveyed have been sinking 9 meters (27) feet a year; in 2002, one great glacial ice shelf jutting from land over the ocean on the Antarctic Peninsula simply disintegrated and floated away within days. NASA's satellite reaches the end of its life this year, and another will not go up until 2015; in the interim, Operation Ice Bridge flights will continue and expand upon the satellite mission.
In addition to lasers, the plane will carry penetrating radars to measure snow cover and the thickness of ice to bedrock, and a gravity-measuring system run by Columbia University's Lamont-Doherty Earth Observatory that will, for the first time, plot the geometry and depth of ocean waters under the ice shelves. The gravity study is seen as key because many scientists believe warm ocean currents may be the main force pulling the ice sheets seaward, melting the undersides of ice shelves and thus removing the buttresses that hold back the far greater masses of ice on land.
"What our colleagues see from modeling of these glaciers is that warm ocean water is providing the thermal energy to melt the ice," said Lamont geophysicist Michael Studinger, a co-leader of the gravity team who will be on some of the flights. "To really understand how the glaciers are going to behave, we need the firsthand measurements of water shape and depth." Earlier this year, an icebreaker cruise co-led by another Lamont scientist, Stan Jacobs, sent an automated submarine to look under the region's Pine Island Glacier, which has been moving forward rapidly in recent years. Its bed, where the ice contacts rock, is below sea level, and scientists are concerned about what would happen if a sudden large movement were to introduce seawater underneath. The plane flights, over some six weeks starting Oct. 15, are aimed at providing a wider-scale picture of Pine Island and other targets.
For each of some 17 flights, the 157-foot DC-8--too big for runways on Antarctic bases--will make an 11-hour round trip from Punta Arenas, Chile, with two-thirds of each trip spent getting to Antarctica. There, the plane will fly survey lines as low as 1,000 feet, some of them along sinuous glacial valleys that may test the nerves of both pilots and scientists. Some flights will investigate the region's open sea ice, which also seems to be in decline. The campaign will cost about $7 million.
"We learned how fast the ice sheets are changing from NASA satellites," said Lamont geophysicist Robin Bell, who is helping lead the project. "These flights are a unique opportunity to see through the ice, and address the question of why the ice sheets are changing."
"A remarkable change is happening on Earth, truly one of the biggest changes in environmental conditions since the end of the ice age," said Tom Wagner, cryosphere program scientist at NASA headquarters in Washington. "It's not an easy thing to observe, let alone predict what might happen next. Studies like this one are key."
Investigators from the University of Washington and University of Kansas will run their own suites of instruments.
Adapted from materials provided by The Earth Institute at Columbia University.

Ice sheet melt threat reassessed

A 3.3m sea level rise will still have a devastating impact on coastal areas The collapse of a major polar ice sheet will not raise global sea levels as much as previous projections suggest, a team of scientists has calculated.Writing in Science, the researchers said that the demise of the West Antarctic Ice Sheet (WAIS) would result in a sea level rise of 3.3m (10 ft). Previous estimates had forecast a rise in the region of five to six metres. However, they added, the rise would still pose a serious threat to major coastal cities, such as New York. "Sea level rise is considered to be the one of the most serious consequence of climate change," lead author Jonathan Bamber told the Science podcast. "A sea level rise of just 1.5m would displace 17 million people in Bangladesh alone," he added. "So it is of the utmost importance to understand the potential threats to coastlines and people living in coastal areas." Threat reassessedProfessor Bamber, from the University of Bristol's Glaciology Centre, said that the WAIS posed "potentially one of the most serious threats".The ebb and flow of sea level rise The world has three ice sheets, Greenland, East Antarctica and West Antarctica, but it is the latter that is considered most vulnerable to climatic shifts. "It has been hypothesised for more than 30 years now that the WAIS is inherently unstable," he explained. "This instability means that the ice sheet could potentially rapidly collapse or rapidly put a lot of ice into the oceans." When the idea first emerged in the late 1970s, it was estimated that global sea level would rise by five metres if the WAIS collapsed. Current projections suggest that a complete collapse of WAIS would result in an increase of up to six metres. But Professor Bamber said that no-one had revisited the calculation, despite new data sets becoming available, and scientists developing a better understanding of the dynamics in the vast ice sheets. The original estimates were based on "very basic ice thickness data", he explained. "Ice thickness data gives you information about the depth of the bedrock underneath the ice sheet. "Over the past 30 years, we have acquired much more ice thickness data over the whole of Antarctica, particularly over West Antarctica. "We also have much better surface topography. Those two data sets are critical in determining two things." The first was knowing the volume of ice that could contribute to sea level rise, and the second was a better understanding of the proportion of WAIS that was potentially susceptible to this instability. Instead of assuming that the entire WAIS would collapse, causing sea level to rise by up to six metres, Professor Bamber and colleagues used models based on glaciological theory to simulate how the 2.2 million-cubic-km ice sheet would respond. "Our reassessment of West Antarctica's contribution to sea level rise if the ice sheet was to collapse is about 3.3 metres," he said. "That is about half of the value that has been quoted up until now."The team's study also calculated what regions were likely to experience the biggest increases in sea level. "Sea level rise is not uniform across the world's oceans, partly as a result of disruptions to the Earth's gravity field," explained Professor Bamber. "It turns out that the maximum increase in sea level rise is centred at a latitude of about 40 degrees along the Atlantic and Pacific seaboards of North America." This would include cities such as San Francisco and New York. These areas could expect increases of one-and-a-quarter times the global average, the team estimated. In other words, if the global average was one metre, then places like New York could expect to see a rise of 1.25m. Responding to Professor Bamber's paper in Science, British Antarctic Survey science leader Dr David Vaughan described the findings as "quite sound". "But for me, the most crucial question is not solely about the total amount of ice in West Antarctica, because that might take several centuries to be lost to the ocean," he told BBC News. "The crucial question is how much ice could be lost in 100-200 years; that's the sea level rise we have to understand and plan for. "Even with this new assessment the loss of a fraction of WAIS over those timescales would have serious consequences and costs that we've only really just begun to understand."

9 polar bears observed on risky open ocean swims

Alaska - Nine polar bears were observed in one day swimming in open ocean off Alaska's northwest coast, an increase from previous surveys that may indicate warming conditions are forcing bears to make riskier, long-distance swims to stable sea ice or land. The bears were spotted in the Chukchi Sea on a flight by a federal marine contractor, Science Applications International Corp.It was hired for the Minerals Management Service in advance of future offshore oil development. The MMS in February leased 2.76 million acres within an offshore area slightly smaller than Pennsylvania.Observers Saturday were looking for whales but also recorded walrus and polar bears, said project director Janet Clark. Many were swimming north and ranged from 15 to 65 miles off shore, she said.Department of Interior Secretary Dirk Kempthorne in May declared polar bears a threatened species because of an alarming loss of summer sea ice and forecasts the trend will continue.Polar bears spend most of their lives on sea ice, which they use as a platform to hunt their primary prey, ringed seals. Shallow water over the continental shelf is the most biologically productive for seals, but pack ice in recent years has receded far beyond the shelf.Conservation groups fear that one consequence of less ice will be more energy-sapping, long-distance swims by polar bears trying to reach feeding, mating or denning areas.Steven Amstrup, senior polar bear scientist for the U.S. Geological Survey in Anchorage, said the bears could have been on a patch of ice that broke up northwest of Alaska's coast."The bears that had been on that last bit of ice that remained over shallow shelf waters, are now swimming either toward land or toward the rest of the sea ice, which is a considerable distance north," he said in an e-mail response to questions.It probably is not a big deal for a polar bear in good condition to swim 10 or 15 miles, Amstrup said, but swims of 50 to 100 miles could be exhausting."We have some observations of bears swimming into shore when the sea ice was not visible on the horizon," he said. "In some of these cases, the bears arrive so spent energetically, that they literally don't move for a couple days after hitting shore."Only further research can tell the effect of greater swimming distances on polar bear populations, he said."Polar bears can swim quite well, but they are not aquatic animals," he said. "Their home is on the surface of the ice."Satellite data Saturday showed the main body of pack ice about 400 miles offshore with one ribbon about 100 miles off Alaska's coast, said Mark Serreze of the National Snow and Ice Data Center.Clark said the animals' origin and destination could not be known without radio collar monitoring."To go out there and say they were going from this point to this point would be complete speculation," Clark said.Observers have no indication of the fate of the nine polar bears observed Saturday.

Antarctic Fish Species Adopts Winter Survival Strategy Similar To Hibernation

Scientists have discovered an Antarctic fish species that adopts a winter survival strategy similar to hibernation। Scientists from British Antarctic Survey (BAS) and the University of Birmingham reveal, for the first time, that the Antarctic 'cod' Notothenia coriiceps effectively 'puts itself on ice' to survive the long Antarctic winter.

The study showed that the fish activate a seasonal 'switch' in ecological strategy -- going from one that maximises feeding and growth in summer to another that minimises the energetic cost of living during the long, Antarctic winter.
The research demonstrates that at least some fish species can enter a dormant state, similar to hibernation that is not temperature driven and presumably provides seasonal energetic benefits. Scientists already know that Antarctic fish have very low metabolic rates and blood 'antifreeze' proteins that allow them to live in near-freezing waters. This study demonstrates that Antarctic fish - which already live in the 'slow lane' with extremely low rates of growth, metabolism and swimming activity - can in fact further depress these metabolic processes in winter.
Lead author Dr Hamish Campbell, formerly at the University of Birmingham, UK but now at University of Queensland, Australia said, "Hibernation is a pretty complex subject. Fish are generally incapable of suppressing their metabolic rate independently of temperature. Therefore, winter dormancy in fish is typically directly proportional to decreasing water temperatures. The interesting thing about these Antarctic cod is that their metabolic rates are reduced in winter even though the seawater temperature doesn't decrease much. It seems unlikely that the small winter reductions in water temperature that do occur are causing the measured decrease in metabolism. However, there are big seasonal changes in light levels, with 24 hour light during summer followed by months of winter darkness -- so the decrease in light during winter may be driving the reduction in metabolic rates."
Dr Keiron Fraser from BAS says, "This is our first insight into how these fish live in winter. We have for the first time in the Antarctic, used cutting edge technologies combining tracking of free swimming fish in the wild and heart rate monitors to allow us to investigate just how these animals cope in winter with living in near freezing water and almost complete darkness for months on end. It appears they utilise the short Antarctic summers to gain sufficient energy from feeding to tide them over in winter. The hibernation-like state they enter in winter is presumably a mechanism for reducing their energy requirements to the bare minimum. The interesting question we still have to answer is why these fish greatly reduce feeding in winter when food is still available."
Why these fish chose to adopt this hibernation-like strategy during winter is currently unclear, but it presumably provides energetic benefits. The traditional views of hibernation are being challenged constantly. This study introduces a new group of animals that appear to utilise a hibernation-like strategy that allows them to survive during the long winters in one of the harshest environments on Earth.
Journal reference: The paper: Hibernation in an Antarctic fish: on ice for winter by Hamish A Campbell, Keiron P P Fraser, Charles M Bishop, Lloyd Peck and Stuart Egginton is published this week in PLoS One 3(3): e1743. doi:10.1371/journal.pone.0001743
About Antarctic cod
The 'Antarctic Cod' (Notothenia coriiceps) became isolated from its warmer water cousins around 30 million years ago when the Antarctic circumpolar current was formed. The olive-coloured fish has a broad head and a narrow body. Whilst scientists know that it has a glycoprotein antifreeze in its blood and it maintains a very low heart rate of less than 10 beats per minute, very little is known about its behaviour or how it evolved to live in Antarctica's extreme environment.
Adapted from materials provided by British Antarctic Survey.

Huddling and a drop in metabolism allow penguins to survive the South Pole cold

Huddling and a drop in metabolism allow penguins to survive the South Pole cold February 01, 2007 - (Bethesda, MD) — March of the Penguins, the Oscar® winning documentary, showed how the emperor penguins endure their incubation and fast for four dark and bitterly cold months each year. The tight huddling among these South Pole penguins is a key energy-saving mechanism that allows them to endure their extremely harsh conditions. A team of scientists that had already shown that emperor penguins who are free ranging in their colony spend about 50 percent of their time in dense huddles and drop their average metabolic rate by 25 percent has questioned whether this drop is due to a process similar to hibernation. Entering into the colony with bulb thermometers, earlier investigators had indeed found that huddling penguins maintain a lower rectal temperature than birds which were isolated from the colony (35.7°C vs. 37.9°C, respectively). However, a sustained drop in deep body (core) temperature would be in direct conflict with the requirements for successful egg incubation. Therefore, energy savings accrued from huddling might rely on mechanisms other than a lower body temperature.To better understand this mechanism, the researchers conducted the first recordings of deep body temperatures in free ranging birds throughout their breeding cycle by using long-term implanted data loggers. The researchers sought to assess whether male emperor penguins lower their deep body temperature during breeding and incubation. Additionally, using external devices during pairing and visual observations of implanted males during incubation, they sought to study deep body temperature variations when the birds were huddling.Study Published in American Journal of Physiology-Regulatory/ComparativeThe authors of the study entitled "Body Temperature Changes Induced by Huddling in Breeding Male Emperor Penguins," are conducted by Caroline Gilbert, Yvon Le Maho and André Ancel, all from the Institut Pluridisciplinaire Hubert Curien, Département Ecologie, Physiologie et Ethologie and Département Interactions Physique, Chimie et Vivant, Centre National de la Recherche Scientifique and Université Louis Pasteur, Strasbourg; and Martine Perret at the Département d'Ecologie et Gestion de la Biodiversité, Centre National de la Recherche Scientifique and Muséum National d'Histoire Naturelle, Brunoy, France. Their findings appear in the January, 2007 edition of the American Journal of Physiology–Regulatory, Integrative and Comparative Physiology.