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Blobrana


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Arctic Coring Expedition
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The IODP Arctic Coring Expedition (ACEX) scientists report their key findings in Nature:

* Evidence of ice in the Arctic Ocean was found much earlier than formerly believed, about 45 million years ago;
* At one time about 55 million years ago, Arctic temperatures rose to subtropical levels (about 23 degrees Centigrade);
* At one time about 49 million years ago, the Arctic was green, with fresh surface water and large amounts of fern covering the water, at least in summer months.

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Blobrana


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Posts: 131433
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RE: Greenhouse Gases
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The Swedish drilling vessel, Vidar Viking, led the Arctic Coring Expedition, when scientists set out to retrieve subseafloor sediment records to support their investigations into climate change.
A group of ocean-drilling research scientists that explored the Arctic Ocean subseafloor in Fall 2004 have released new findings in a report to be published in Nature on June 1. The report, supported by Integrated Ocean Drilling Program (IODP) research operations, contains analyses of subseafloor sediment samples gathered from 430 meters beneath the Arctic Ocean, near the North Pole. To recover the sediments that yielded the prehistoric climate records, the research team needed to manage three ice-breakers, one of which was equipped with a drill rig. The sediment records were recovered from the Lomonsov Ridge, in water about 1000 meters deep.

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Blobrana


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Posts: 131433
Date:
The North Pole
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Fifty-five million years ago the North Pole was an ice-free zone with tropical temperatures, according to research.

A sediment core excavated from 400m below the seabed of the Arctic Ocean has enabled scientists to delve far back into the region's past.
An international team has been able to pin-point the changes that occurred as the Arctic transformed from green house to ice house.
The findings are revealed in a trio of papers published in the journal Nature.

north pole

In 2004, the Arctic Coring Expedition (Acex) used ice-breaking ships and a floating drilling rig to remove 400m-long cylinders of sediment from the bottom of the ocean floor. The cores were taken from the 1,500km long Lomonosov Ridge, which stretches between Siberia and Greenland.
The cores revealed that before 55 million years ago, the surface waters of the Arctic Ocean were ice-free and as warm as 18C.
A sudden increase in greenhouse gasses boosted them to a balmy 24C (74F) and the waters suddenly filled with a tropical algae Apectodinium.
When current climate models were applied to this period of the Earth's history they predict North Pole temperatures to be about 15C lower than the core shows.

"Today's warming of the Arctic can, in all likelihood, be attributed to mankind's impact on the planet, but as our data suggest, natural processes operating in the past have also resulted in a significant warming and cooling of the Arctic" - Appy Sluijs, palaeoecologist from Utrecht University in the Netherlands, and the lead author on one of the papers.

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Blobrana


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Date:
Climate Change
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What do month-to-month changes in temperature have to do with century-to-century changes in temperature? At first it might seem like not much. But in a report published in this week’s Nature, scientists from the Woods Hole Oceanographic Institution (WHOI) have found some unifying themes in the global variations of temperature at time scales ranging from a single season to hundreds of thousands of years. These findings help place climate observed at individual places and times into a larger global and temporal context.

"Much of the work went into assembling the different types of records needed to study such diverse time scales. Data from instruments from around the world are available for recent periods, but it is not so easy for earlier times. We have few instrumental records before the 19th century, so we have to use measurements in corals, ice cores, and sediment cores to estimate past temperatures" - Peter Huybers, paleoclimatologist in the Geology and Geophysics Department at WHOI and lead author on the study.

These measurements and data compilations were made by scientists at WHOI and other research institutions.

"While none of the measurements we use are new, putting them together told us more than we could learn from any single record" - Peter Huybers.

Huybers and coauthor William Curry, a senior scientist and paleoceanographer at WHOI, found that temperature variations are more intimately linked across time scales than had previously been thought. For example, places that have a large annual cycle in temperature, like the high latitudes, also have a lot of interannual and decadal temperature variability. In fact, the relationship is so strong Huybers says you can fairly well predict how much decadal temperature change occurs at a given location simply by knowing the size of the annual cycle.
At longer time scales, however, a different relationship seems to hold. Temperature variations at thousands and tens of thousands of years seem to follow temperature variations at the Milankovitch cycles. Milankovitch cycles are named after the Serbian mathematician Milutin Milankovitch, who argued that periodic changes in the Earth's orbit around the Sun cause the advance and retreat of massive ice sheets. The changes in Earth’s orbit cause redistributions in how much sunlight the Earth receives at different locations and seasons.

"The overall impression is that energy is put into the climate system at the annual and Milankovitch time scales, causing temperature variations at those time scales, but also at the neighbouring time scales" - Peter Huybers.

In the tropics the amplitude of the annual and Milankovitch cycles tends to be smaller than at high latitudes and, correspondingly, there is less tropical temperature change across interannual to thousand-year time scales. Another notable feature is that the variability of temperature appears most similar globally at those time scales furthest removed from the annual and Milankovitch time periods, indicating that away from these forcing periods climate relaxes to a more uniform background state.
Climate varies at all time scales, from months to millions of years and longer. These changes are often studied independently of one another, but now there is a clearer idea of how climate change is linked across time scales.

"These insights may help us to better understand past temperature changes, improve our models of the climate, and maybe even predict future climate change" - Peter Huybers.

Source

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Blobrana


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A University of Alberta anthropologist is heading up an international research team that will investigate why an entire Siberian culture of hunter-gatherers vanished between 7000 and 6000 BC.

On Tuesday, Social Science and Humanities Research Council (SSHRC) announced $2.5 million for the project that will examine human remains from ancient cemeteries in the Lake Baikal region of Russia. It is thought that climate change could be a key factor in the disappearance of people from this area, as it might have dramatically affected culture, diet and migration.

Lead researcher Dr. Andrezej Weber explained that the project will involve several months of field work in Siberia this summer, followed by extensive analysis of the collected data back at the University of Alberta. The work will include DNA analysis, radiocarbon dating and climate modelling to help uncover the daily life within the culture, the environmental conditions of the time and whether groups that appeared a millennium later were genetically similar to the first peoples.

"There is a very interesting basic research problem: a history of a human culture in this particular part of the region that's very different from other parts of the world and similar to only a few other parts of the world. From these comparisons you can draw conclusions about why human cultures evolved in certain ways" - Dr. Andrezej Weber.

Weber added that while the project will uncover information about a culture that existed many thousands of years ago, the research is relevant now.

"We're looking at climate change back 5,000 years ago which is very similar to what the north is experiencing today". Weber explained that the research could help predict how places in the north, like Siberia and northern Canada, will change with regard to "animal distribution, habitats, and the potential for traditional lifestyles to continue."

Weber's research team will include 29 anthropology, archaeology, geography, genetics and climate change experts from universities in Russia, Britain, Canada and the United States, as well as more than 50 graduate students.

"While our project is based in Siberia, we have collaborators from so many countries, that it provides an excellent platform for the flow of ideas, hypotheses, interactions, networking. This is what international research is really all about - to provide the scientific environment for people to interact, and our project is very friendly in this regard." - Dr. Andrezej Weber.

The project will also provide an excellent training opportunity for budding scientists.

"We're not just training undergraduate students, we're training everyone: from undergraduate students to graduate students to post-doctoral fellows. We're also helping young scholars to build their careers."

In the end, Weber hopes to discover a great deal about how these ancient people lived and, despite the new technology available, there are always limits to what can be known.

"In archaeology you never get to see the full story, as there are these small pieces to the puzzle. In the best case scenario, most of the picture's still missing - for the rest you need to use your imagination."

Source

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Blobrana


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Using chemical clues mined from ocean mud, Brown University researchers have generated the longest continuous record of ocean temperatures on Earth.

The 5-million-year record is a history of temperatures in the eastern equatorial Pacific, or EEP, located off the coast of South America. The area is an anomaly – a huge swath of cool water in the tropics – that plays an important role in global climate. In the EEP, trade winds pull nutrient-rich cold water to the surface, which makes for fertile fisheries off the coasts of Peru, Chile and Ecuador. The interplay of wind and water can also fuel El Niño events, a large-scale warming in the EEP that slows the upwelling of cold water and forces changes in weather, such as droughts or floods, far from the tropical Pacific.

In the EEP, the Brown geology team found that surface temperatures were 27° C 5 million years ago. Surface temperatures are 23° C today. In between, they found a pattern of steady cooling – roughly one degree Celsius every million years.

This finding, published in Science, contradicts the long-standing notion that rapid glacier growth in the high northern latitudes about 3 million years ago alone set off dramatic cooling of the global climate. The finding shows instead that glaciation was part of a long-term cooling trend.
The climate record suggests that ocean regions near Antarctica were the main driver of EEP cooling by continuously pumping cold water into the area. This finding was bolstered by additional evidence that glacial cycles affected the tropical Pacific long before the advent of large ice sheets in the Northern Hemisphere.

"The Southern Hemisphere, not the Northern Hemisphere, more likely had a stronger effect on temperature and productivity in the eastern Pacific. We may need to refocus where we look to understand the evolution of climate over the past 5 million years." - Kira Lawrence, graduate student in the Department of Geological Sciences and the lead author of the Science paper.

Lawrence, post-doctoral research fellow Zhonghui Liu, and Professor Tim Herbert used sediment cores pulled from hundreds of meters below the surface of the Pacific by a ship operated by the Ocean Drilling Program, an international research organization. Moving down the cores, collecting small samples of gray mud, scientists can go back in time. The end result: Thousands of glass vials filled with climate history.

But how do you extract history from mud? The answer was found in tiny marine fossils.

To date the sediments, the geologists analysed fossils and traces of oxygen trapped in the shells of microscopic ocean organisms. To get temperatures, the Brown team looked to algae, infinitesimal surface-dwellers that produce fatty compounds called alkenones. Algae crank out two kinds of alkenones depending on the surrounding water temperature. When water is cooler, algae make more of one kind. When water is warmer, they produce more of another. By carefully measuring the amount of these alkenones in each sample, researchers were able to calculate past surface temperatures.

The resulting 5-million-year timeline might have a practical use. Scientists trying to predict future climate change may use the data in computer simulations that model natural climate variability as well as predict the impact of accelerated warming due to greenhouse gas emissions.

The work has other implications for understanding climate change.

"Results from the past prove that it is possible for the EEP to exist in a kind of permanent El Niño state, which would have immense climate and biological repercussions if it were to happen again under global warming. The geological evidence also suggests that to predict warming in the EEP, the key ocean region to monitor is near Antarctica." - Professor Tim Herbert.

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Blobrana


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Posts: 131433
Date:
Climate Warming
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NASA Survey Confirms Climate Warming Impact on Polar Ice Sheets

In the most comprehensive survey ever undertaken of the massive ice sheets covering both Greenland and Antarctica, NASA scientists confirm climate warming is changing how much water remains locked in Earth's largest storehouses of ice and snow.

"If the trends we're seeing continue and climate warming continues as predicted, the polar ice sheets could change dramatically. The Greenland ice sheet could be facing an irreversible decline by the end of the century" - Jay Zwally, survey lead author, NASA's Goddard Space Flight Centre.

Other recent studies have shown increasing losses of ice in parts of these sheets. This new survey is the first to inventory the losses of ice and the addition of new snow on both continents in a consistent and comprehensive way throughout an entire decade.
The survey shows there was a net loss of ice from the combined polar ice sheets between 1992 and 2002 and a corresponding rise in sea level. The survey documented for the first time extensive thinning of the West Antarctic ice shelves, an increase in snowfall in the interior of Greenland and thinning at the edges. All are signs of a warming climate predicted by computer models.
The survey combines new satellite mapping of the height of the ice sheets from two European Space Agency satellites. It also used previous NASA airborne mapping of the edges of the Greenland ice sheets to determine how fast the thickness is changing. Researchers used nine years of elevation mapping over much of Antarctica and 10.5 years of data over Greenland from the European Remote-sensing Satellites 1 and 2. The survey pinpointed where the ice sheets were thinning and where they were growing.
In Greenland, the survey saw large ice losses along the south-eastern coast and a large increase in ice thickness at higher elevations in the interior due to relatively high rates of snowfall. This study suggests there was a slight gain in the total mass of frozen water in the ice sheet over the decade studied, contrary to previous assessments.

According to Zwally, this situation may have changed in just the past few years. Last month NASA scientists at the Jet Propulsion Laboratory, Pasadena, California, US, reported a speed up of ice flow into the sea from several Greenland glaciers. That study included observations through 2005; Zwally's survey concluded with 2002 data.

"The melting of ice at the edges of the ice sheet is also increasing, which causes the ice to flow faster. A race is going on in Greenland between these competing forces of snow build-up in the interior and ice loss on the edges. But we don't know how long they will be approximately in balance with each other or if that balance has already tipped in favour of the recently accelerating outflow from glaciers"- Jay Zwally.

The situation was very different in Antarctica. The ice sheets had a major net loss of ice due to outflow from West Antarctica. These loses, which may have been going on for decades, outweighed the gains in snow and ice seen in the East Antarctic ice sheet and parts of West Antarctica. Also thinning were the ice shelves around West Antarctica, where temperatures have been increasing. The floating ice shelves are vulnerable to climate change. Some ice shelves in the Antarctic Peninsula have totally disintegrated in recent years, allowing the ice from the land to move into the ocean faster.
When the scientists added up the gains and loses of ice from the Greenland and Antarctic sheets, there was a net loss of ice to the sea. The Greenland ice sheet annually gained approximately 11 billion tons of water, while Antarctica lost about 31 billion tons per year. The 20 billion net tons added to the oceans is equivalent to the amount of fresh water annually used in homes, businesses and farming in New York, New Jersey and Virginia.

"The study indicates that the contribution of the ice sheets to sea-level rise during the decade studied was much smaller than expected, just two percent of the recent increase of nearly three millimetres a year. Current estimates of the other major sources of sea-level rise - expansion of the ocean by warming temperatures and runoff from low-latitude glaciers - do not make up the difference, so we have a mystery on our hands as to where the water is coming from. Continuing research using NASA satellites and other data will narrow the uncertainties in this important issue and help solve the mystery"- Jay Zwally.

The survey was published this week in the Journal of Glaciology (www.igsoc.org).

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Blobrana


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Posts: 131433
Date:
RE: Greenhouse Gases
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Two British scientists have used tree rings, ice cores, fossil shells and other data to confirm that roughly a millennium ago, between A.D. 890 and 1170, the world was considerably warmer than at any time until the past century.

Their research also shows that modern warming is much more extensive than it was then.
Around that time, known as the Medieval Warm Period, the Vikings occupied Greenland. In the Pacific, Polynesians were new in Hawai'i. New Zealand, or Aotearoa, and Easter Island, or Rapa Nui, were being settled.
Climate scientists Timothy Osborn and Keith Briffa of the University of East Anglia, UK, compared modern and ancient "climate proxies" such as tree rings from all over the Northern Hemisphere to arrive at their temperature estimates.
Many scientists believe that modern warming is partly caused by human activities such as burning fossil fuels.

But what was making it warm 1,000 years ago? It is likely it had to do with volcanic activity — or rather, the lack of it.

If methane and carbon dioxide are pumped into the atmosphere, temperatures rise. But if volcanic emissions are pumped into the atmosphere in the form of sulphate droplets, temperatures fall.

"It is the 'explosive' type of volcanoes that can have an influence on the climate, because those are the ones that can shoot material up into the stratosphere, where it can stay for a number of years and, therefore, affect the climate for a number of years" - Timothy Osborn .

The Medieval Warm Period was probably an era with very little volcanic activity, which allowed the planet to warm up more than normal. The sun also may have been putting out a little more energy than normal near the end of the period, adding to the warmth.
While those things could be having a small effect today, humans are mainly responsible for modern warming.

"The combination of natural changes in sun energy and volcanic activity cannot explain the warming found in the last 100 years. They might contribute a small amount, but that is all. The bulk of the recent warming is likely to be caused by man-made emissions of greenhouse gases" - Timothy Osborn .

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Blobrana


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Posts: 131433
Date:
Global Warming
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Human activities are releasing greenhouse gases more than 30 times faster than the rate of emissions that triggered a period of extreme global warming in the Earth's past, according to an expert on ancient climates.

"The emissions that caused this past episode of global warming probably lasted 10,000 years. By burning fossil fuels, we are likely to emit the same amount over the next three centuries" - James Zachos, professor of Earth sciences at the University of California, Santa Cruz.

Zachos presented his findings this week at the annual meeting of the American Association for the Advancement of Science (AAAS) in St. Louis. He is a leading expert on the episode of global warming known as the Paleocene-Eocene Thermal Maximum (PETM), when global temperatures shot up by 5 degrees Celsius. This abrupt shift in the Earth's climate took place 55 million years ago at the end of the Paleocene epoch as the result of a massive release of carbon into the atmosphere in the form of two greenhouse gases: methane and carbon dioxide.

Previous estimates put the amount of released carbon at 2 trillion tons, but Zachos showed that more than twice that amount--about 4.5 trillion tons--entered the atmosphere over a period of 10,000 years. If present trends continue, this is the same amount of carbon that industries and automobiles will emit during the next 300 years.

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Blobrana


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Posts: 131433
Date:
Antarctica Ice Cores
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Japanese scientists have drilled more than 3 kilometres into Antarctica's ice sheet to study the earth's past climate.
The ice cores are among the oldest samples yet extracted by scientists and trapped bubbles of gas, such as carbon dioxide in the core samples, will offer clues to past patterns of global climate change.

The ice cores give a million-year-old record of greenhouse gases, such as carbon dioxide and methane .

"By analysing the ice we would like to decipher climate and temperature conditions that stretch back to ages that have not been clarified before" - Yoshiyuki Fujii, director-general of the National Institute of Polar Research.

The samples would explain changes to the earth's climate from an inversion of the earth's magnetic field that occurred around 790,000 years ago. During such an event, the earth's magnetic poles switch entirely.
The team in Antarctica drilled near their base located on the Queen Maud Land dome (77o22'S, 39o37'E, 3,807m above sea level) in the east Antarctic inland area.
The samples would be brought to Japan for analysis.
This is believed to be the oldest sample allowing such analysis, although isolated ice samples believed to be about six million years old have previously been found.
Last year, several European studies of Antarctic ice core samples released findings that showed current levels of methane and carbon dioxide in the atmosphere are higher than at any time in the past 650,000 years.
Scientists in those studies also drilled down to about three kilometres.

Many scientists believe rising levels of carbon dioxide released from burning fossil fuels and methane from agriculture are warming the atmosphere, threatening to cause greater extremes of weather, melting ice caps and rising sea levels.
Scientists said last year was the second warmest year on record since 1860 and that eight of the 10 warmest years since records began have occurred in the past decade.

http://www.nipr.ac.jp/jare/

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