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Posts from the ‘Environment’ Category

Oxygen Levels Depleated Off Northwest Coast

“We’re now seeing low oxygen levels that are much more widespread and far more intense than what has been recorded in the past,” according to William Peterson, one of the researchers and an oceanographer at the NOAA Fisheries Service’s science center in Newport, Ore.

“The fish have simply moved out of these areas and are probably doing fine elsewhere,” said Peterson. “But animals that can’t move to better waters like Dungeness crabs, sea urchins and starfish will perish.”

Peterson added that during the summer of 2006, anoxia – a complete lack of oxygen in the water – was recorded off the central Oregon coast for the first time.

In a paper published today in Science magazine, the researchers say that data going back to the 1950s show little evidence of widespread low-oxygen levels along the narrow continental shelf before about 2000. Since then conditions have begun to change.

The team conducted a submersible-based survey in the summer of 2006 and discovered no fish living along the rocky reefs that are normally healthy habitat for varieties of commercially important rockfishes. This is in contrast to similar surveys completed from 2000 through 2004 which registered abundant fish populations. In shallow areas in particular, the team found almost complete absence of bottom-dwelling organisms and a rise in bacteria that flourish under conditions of little or no oxygen.

Although the causes of these low- and no-oxygen conditions are not fully understood, it is known that low-oxygen water is associated with coastal upwelling – the process by which nutrient-rich waters are brought from deep water to the sea surface. There these nutrients fuel extraordinarily high production of tiny plants and animals off the coasts of the Pacific Northwest during summer.

Eventually, much of this plankton production dies and falls to the seafloor where it decomposes, reducing the water’s oxygen content, and causing hypoxia (low oxygen) or even anoxia (no oxygen).
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Source:
http://www.nmfs.noaa.gov/mediacenter/docs/021508_nw_anoxia_FINAL.pdf

North Atlantic slows on the uptake of CO2

Further evidence for the decline of the oceans’ historical role as an important sink for atmospheric carbon dioxide is supplied by new research by environmental scientists from the University of East Anglia.

Since the industrial revolution, much of the CO2 we have released into the atmosphere has been taken up by the world’s oceans which act as a strong ‘sink’ for the emissions.

This has slowed climate change. Without this uptake, CO2 levels would have risen much faster and the climate would be warming more rapidly.

A paper in the Journal of Geophysical Research by Dr Ute Schuster and Professor Andrew Watson of UEA’s School of Environmental Sciences again raises concerns that the oceans might be slowing their uptake of CO2.

Results of their decade-long study in the North Atlantic show that the uptake in this ocean, which is the most intense sink for atmospheric CO2, slowed down dramatically between the mid-nineties and the early 2000s.

A slowdown in the sink in the Southern Ocean has already been inferred, but the change in the North Atlantic is greater and more sudden, and could be responsible for a substantial proportion of the observed weakening.

The observations were made from merchant ships equipped with automatic instruments for measuring carbon dioxide in the water. Much of the data has come from a container ship carrying bananas from the West Indies to the UK, making a round-trip of the Atlantic every month. The MV Santa Maria, chartered by Geest, has generated more than 90,000 measurements of CO2 in the past few years.

The results show that the uptake by the North Atlantic halved between the mid-90s, when data was first gathered, and 2002-05.

“Such large changes are a tremendous surprise. We expected that the uptake would change only slowly because of the ocean’s great mass,” said Dr Schuster.

“We are cautious about attributing this exclusively to human-caused climate change because this uptake has never been measured before, so we have no baseline to compare our results to. Perhaps the ocean uptake is subject to natural ups and downs and it will recover again.”

But the direction of the change was worrying, she added, and there were some grounds for believing that a ‘saturation’ of the ocean sink would start to occur.

“The speed and size of the change show that we cannot take for granted the ocean sink for the carbon dioxide. Perhaps this is partly a natural oscillation or perhaps it is a response to the recent rapid climate warming. In either case we now know that the sink can change quickly and we need to continue to monitor the ocean uptake,” said Prof Watson.
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Link to the United Kingdom’s University of East Anglia below:
http://comm.uea.ac.uk/press/release.asp?id=796

Cave Records Provide Clues to Climate Change

Deer Cave

Deer Cave

Growing inside the caves of the tropical Pacific island of Borneo are some of the keys to understanding how the Earth’s climate suddenly changed – several times – over the last 25,000 years. By analyzing stalagmites, the pilar-like rock formations that stem from the ground in caves, they were able to produce a high-resolution and continuous record of the climate over this equatorial rainforest.

“These stalagmites are, in essence, tropical ice cores forming over thousands of years,” said Partin. “Each layer of the rock contains important chemical traces that help us determine what was going on in the climate thousands of years ago, much like the ice cores drilled from Greenland or Antarctica.”

The tropical Pacific currently plays a powerful role in shaping year-to-year climate variations around the globe (as evidenced by the number of weather patterns influenced by the Pacific’s El Nino), but its role in past climate change is less understood. Partin and Cobb’s results suggest that the tropical Pacific played a much more active role in some of the abrupt climate change events of Earth’s past than was once thought and may even have played a leading role in some of these changes.

Polar ice cores reveal that the Northern Hemisphere and the Southern Hemisphere each have their own distinct patterns of abrupt climate change; the tropical Pacific may provide the mechanistic link between the two systems. Understanding how the climate changes occurred and what they looked like is important to helping scientists put into context the current trends in today’s climate. They published their findings in the Sept 27, 2007, issue of the journal Nature.

The research team collected stalagmites from the Gunung Buda cave system in Borneo in 2003, 2005 and 2006. Analyzing three stalagmites from two separate caves allowed the pair to create a near-continuous record of the climate from 25,000 years ago to the present. While this study is not the first to use stalagmites to examine climate over this time period, it is the first to do so in the tropical Pacific. Typically, in these types of studies, only one stalagmite is analyzed, but Partin and Cobb compared their three stalagmite records to isolate shared climate-related signals.

Stalagmites are formed as rain water, mixed with calcium carbonate and other elements, makes its way through the ground and onto the cave floor. As this solution drips over time, it hardens in layers, creating a column of rock.

Partin and Cobb cut open each stalagmite and took 1,300 measurements of their chemical content to determine the relative moisture of the climate at various periods in history starting from the oldest layers at the bottom to the present at the top. They dated the rocks by analyzing the radioactive decay of uranium and thorium, and determined the amount of precipitation at given times by measuring the ratio of oxygen isotopes.

“Our records contain signatures of both Northern and Southern Hemisphere climate influences as the Earth emerged from the last ice age, which makes sense given its equatorial location,” said Cobb. “However, tropical Pacific climate was not a simple linear combination of high-latitude climate events. It reflects the complexity of mechanisms linking high and low latitude climate.”

For example, Partin and Cobb’s records suggest that the tropical Pacific began drying about 20,000 years ago and that this trend may have pre-conditioned the North Atlantic for an abrupt climate change event that occurred about 16,500 years ago, known as the Heinrich 1 event.
“In addition, the Borneo records indicate that the tropical Pacific began to get wetter before the North Atlantic recovered from the Heinrich 1 event 14,000 years ago. Perhaps the tropical Pacific is again driving that trend,” said Partin.

“Currently our knowledge of how these dramatic climate changes occurred comes from just a few sites,” said Cobb. “As more studies are done from caves around the world, hopefully we’ll be able to piece together a more complete picture of these changes. Understanding how the dominoes fell is very important to our understanding of our current warming trend.”