Environmental Hotspot Alert

Loss of ancient ice—Larsen Ice Shelf, Antarctic Peninsula 2002-2006

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Over the past 30 years, the ice along the Antarctic Peninsula has been disappearing in a series of retreats. Climate in this area is warming at approximately 0.5 degrees Celsius per year following a trend that is believed to have been taking place for at least the past 50 years. Generally, this retreat has occurred as icebergs break away from the oceanward edge of the ice.

More recently, scientists have observed a new pattern. They have been closely monitoring the Larsen Ice Shelf since 1995, when a large portion of it (Larsen A) dramatically disintegrated. In 2002, another similar event occurred at Larsen B. In contrast to the slower pattern of calving—when pieces of ice break away at the edge of the shelf—these two events occurred over a large area in a relatively short period of time. In the case of Larsen B, 3 250 km2 of the ice shelf shattered into a plume of thousands of icebergs in a little over a month. Over the last 5 years, 5 700 km2 has disintegrated, representing approximately 40 per cent of Larsen B. At the time of its collapse, it is thought that Larsen A had been in place for over 2000 years and Larsen B is believed to have been older still.

Scientists have developed a theory to explain this new phenomenon of catastrophic collapse, linking it to summertime warming and the pooling of melted water on the surface of the ice shelf. The pooling water is believed to accelerate the expansion of crevasses and lead to the breakdown of the ice shelves. In the case of Larsen B, ponds of melt water can be seen in the remote sensing images taken shortly before the collapse occurs, lending credence to this theory. In more recent images, melt-water ponds can now be seen forming on Larsen C, suggesting the potential for a similar collapse there in the future.

Source: http://na.unep.net/atlas/webatlas.php?id=265

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Environmental Science Alert

Plants fail to take up carbon from thawing permafrost in the long term

Almost double the amount of carbon found in the atmosphere is stored in permafrost that has accumulated over thousands of years in the world's boreal and Arctic ecosystems. A warming climate will thaw the permafrost, causing microbes to decompose and the stored carbon to be released to the atmosphere, potentially increasing the greenhouse effect. It is important to know the strength and timing of this positive feedback system so scientists can better determine the role of thawing permafrost on the future climate. Researchers looked at old carbon, which forms the bulk of the permafrost carbon pool, at a site in Alaska that had experienced permafrost thawing since before the 1990s. In places that had been thawing over the past 15 years, there was a 40 per cent greater loss of old carbon than in areas that were only minimally thawed. As the climate warmed and vegetation increased in what had been frozen ground, however, plant growth had absorbed both the lost carbon and atmospheric carbon, so there was a net uptake in greenhouse gases. A tempting conclusion to draw might be that increased plant growth in thawing permafrost helps to slow climate change. But the researchers found that in areas that have been thawing for more than 15 years, plants no longer compensate for the losses and these places lost 78 per cent more carbon to the atmosphere than did minimally thawed areas. They concluded that over decades of thawing, losses of soil carbon overwhelm the ability of plants to take up the gases, making permafrost a large source of carbon in an already warming climate. In fact, at some point, the amount could match current carbon contributions from land-use change such as deforestation and land degradation.

Source: Schuur, Edward A. G., Jason G. Vogel, Kathryn G. Crummer, Hanna Lee, James O. Sickman, and T. E. Osterkamp. "The effect of permafrost thaw on old carbon release and net carbon exchange from tundra." Nature 459 (May 2009): 556-559.

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Near Real-Time Environmental Event Alert

Predicted return of El Niño

Comparison of sea-surface temperatures in May 2009 with the mean sea-surface temperature calculated for 1951-1980 shows a pattern of above average temperatures developing in the eastern equatorial Pacific Ocean. This pattern is associated with the El Niño climate phenomena.

The National Centers for Environmental Prediction (NCEP) of the US National Oceanic and Atmospheric Administration (NOAA) reported changes in sea surface temperatures of the equatorial eastern Pacific Ocean in late May 2009. They say this pattern typically precedes the development of the El Niño southern oscillation climate phenomenon. El Niño is a pattern in the ocean-atmosphere circulation system of the tropical Pacific Ocean that influences weather patterns around the globe. Warmer sea-surface temperature in the eastern Pacific and cooler surface temperature in the western Pacific increase the winter rainfall and flooding over Peru and the southeastern U.S. and cause increased drought in Indonesia and Australia. The phenomena has ripple effects felt as far away as India and East Africa; during the northern hemisphere winter months, it causes wetter than normal patterns in northern East Africa and drier than normal ones in southern East Africa. It is also associated with drier weather and an increase in extreme warm temperatures across much of India, particularly in the summer.

PMEL (no date)

The International Research Institute for Climate and Society (IRI) tracks 14 dynamical models, such as the one used by the National Centers for Environmental Prediction. It found that almost all models forecast the onset of El Niño during June through August of 2009. All eight statistical models monitored by IRI, however, are still predicting neutral conditions through the same time period. NCEP updates its predictions monthly and will issue its next update on 9 July 2009.

Sources: NOAA (2009) El Nino/southern Oscillation (ENSO) Diagnostic Discussion, from Climate Prediction Center/NCEP/NWS 4 June 2009

PMEL (n.d.). Pacific Marine Environmental Laboratory's El Niño Theme Page. Accessed on 15 June 2009. Available at http://www.pmel.noaa.gov/tao/elnino/nino-home.html

IRI (2009) Summary of ENSO Model Forecasts. Accessed on 15 June 2009 on the International Research Institute for Climate and Society webpage: http://portal.iri.columbia.edu/portal/server.pt?open=512&objID=945&PageID=0&cached=true&mode=2&userID=2

GISS (2009) Base map image of sea surface temperature anomalies for May 2009 as compared to base period 1951 to 1980 generated using the GISS Surface Temperature Analysis tool of the Goddard Institute for Space Studies at: http://data.giss.nasa.gov/gistemp/maps/

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