1. Greenland cools as the globe warms
2. Ice cores tell of recent tropical climate change
3. Black water hits Florida Keys coral reef
4. Warmer temperatures predicted for Arctic Ocean
5. Sea ice's effect on oceanic deepwater
6. Anthropogenic gases lead to stratospheric cooling
7. Methane increase warmed prehistoric Earth
8. Designing a cheaper, smaller weather radar satellite

Greenland's land and ice sheet have cooled significantly over the past 40 years, even as much of the rest of the world has warmed in the recent past. Hanna and Cappelen analyzed temperature records from southern Greenland, finding evidence of a cooling trend that they believe is associated with an increased phase of the North Atlantic Oscillation (NAO) that has been observed over the past 35 years. They believe that the NAO is likely causing the temperature reductions along the Greenland coast and is responsible for slowing the island's ice melting rate, in contrast to evidence of global warming. The lowered temperatures may also have
significantly added to the island's ice sheet, particularly along its southern coast, although they note that it is difficult to assess the long-term ice effects from the current NAO trend.

Title: Recent cooling in coastal southern Greenland and relation with the North Atlantic Oscillation

Authors:
Edward Hanna, University of Plymouth, UK;
John Cappelin, Danish Meteorological Institute, Copenhagen, Denmark.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL01597, 2003

New ice core samples from the Andean mountain range may help resolve longstanding discrepancies in the climate record in the tropics. Hoffmann et al. analyzed a nearly century-long sample of detailed isotopic water records from ice cores in two high-altitude locations in Bolivia and suggest that their data could be combined
with previous records to create a better approximation of the hydrological cycle during the past centuries. Previous estimates varied widely in projecting the causes and dates for climate change in the region, because of difficulty in establishing the conditions responsible for the material found in the ice. The researchers compared their findings with historical meteorological records and believe that El Nino climate variability controls the precipitation over the Amazon basin and conclude that the ice cores closely approximate the precipitation over the area.

Title: Coherent isotope history of Andean ice cores over the last century

Authors:
Georg Hoffmann, M. Stievenard, National Committee for Research Science, Gif sur Yvette, France;
E. Ramirez, J. D. Taupin, B. Francou, P. Ribstein, R. Gallaire, Great Ice Research Unit, Paris France;
R. Delmas, J. Simoes, Environmental Laboratory of Glaciology and Geophysics, Grenoble, France;
H. Durr, University of Pierre and Marie Curie, Paris, France;
U. Schotterer, Bern University, Berne, Switzerland; M. Werner, Max-Planck Institute for Biogeochemistry, Jena, Germany.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL014870, 2003

A patch of "black" water may have recently contributed to a severe coral reef decline in the Florida Keys. Ocean color observations reported by Hu et al. indicated that dark water spread through a section of the delicate ecosystem north of Key West in the spring of 2002, killing a large swath of the reef life. Satellite and ship observations showed that the water contained particularly high concentrations of tiny organisms that cause a "red tide," which is known to be hazardous to fish and living sediment on the ocean floor. The researchers noted a 70 percent decrease in the stony coral on the reef, a 40 percent reduction of all coral and a near-elimination of sponge colonies after the dark water's passage. The authors to suggest that the coral reef was likely killed by the organisms and toxins from the water, which was then recirculated by an anticyclonic current off the Florida coastline.

Title: The 2002 ocean color anomaly in the Florida Bight: A cause of local coral reef decline?

Authors:
Chuanmin Hu, Serge Andrefouet, Frank E. Mullen-Karger, University of South Florida, St. Petersburg, Florida;
Keith E. Hackett, Michael K. Callahan, Jennifer L. Wheaton, Florida Fish and Wildlife Conservation Commission, St. Petersburg, Florida;
James W. Porter, University of Georgia, Athens, Georgia.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016479, 2003

A recently observed episode of warming in the Arctic Ocean waters simulated by an ocean-ice model has provided evidence that another such event is now active and will likely last through the coming decade. Karcher et al. analyzed nearly 20 years of simulated versus observed ocean temperature data in the Arctic while seeking the cause for several anomalously high water temperature readings in the ocean's Atlantic layer during the 1990s. They suggest that a combination of a stronger North Atlantic Oscillation, a strong northward flow of water and higher air temperatures contributed to that warming, which elevated temperatures in the central Arctic up to 1 degree Celsius [2 degrees Fahrenheit] and resulted in a large, warm body of water that will circulate in the Arctic for another decade. They conclude that the warming was likely an unusual incident caused by the confluence of sources, rather than evidence of a continuing warming trend.

Title: Arctic warming: Evolution and spreading of the 1990s warm event in the Nordic seas and the Arctic Ocean

Authors:
Michael J. Karcher, Rudiger Gerdes, Frank Kauker, Cornelia Koberle, Alfred-Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.

Source: Journal of Geophysical Research-Oceans (JGR-C) paper: 10.1029/2001JC001265, 2003

Fresh water added to the ocean from sea ice melting has a more significant effect on the global thermohaline circulation [vertical movement of seawater] than previously believed. Komuro and Hasumi used a coupled sea ice-ocean model of the Southern Ocean to analyze the effects of sea ice on dense, cold deepwater
formation. As wind carries ice floes to lower latitudes, changes in salt input and melting freshwater modify the water density and affect the world's oceanic thermohaline circulation. The authors conclude that their model can more accurately project the amount of freshwater entering the oceans from sea ice, which may help researchers better estimate ocean circulation patterns and produce more accurate climate estimates based on the ocean's salinity.

Title: Effects of surface freshwater flux induced by sea ice transport on the global thermohaline circulation

Authors:
Yoshiki Komuro, Hiroyasu Hasumi, University of Tokyo, Tokyo, Japan.

Source: Journal of Geophysical Research-Oceans (JGR-C) paper: 10.1029/2002JC001476, 2003

Man-made changes to the concentration of atmospheric greenhouse gases are likely responsible for lower temperatures and decreased ozone observed in the stratosphere during the past 20 years. Langematz et al. compared climate simulations to stratospheric temperature and circulation observations over the last two decades, finding that decreases in manmade mid-atmosphere ozone and increases in carbon dioxide affect Arctic atmospheric conditions. Contrasting observations with expected model predictions over Europe, they suggest that the gases have led to a trend toward cooling in the lower stratosphere in the mid-latitudes and Arctic, particularly during springtime. They suggest that cooling of the lower stratosphere cannot be fully explained by the composition changes from greenhouse gas changes and narrows the likely source of cooling to either direct radiative forcing from sunlight or indirect dynamic processes. The authors conclude that changes to stratospheric ozone and carbon dioxide can intensify and increase the lifetime of polar vortices.

Title: Thermal and dynamical changes of the stratosphere since 1979 and their link to ozone and CO2 changes

Authors:
Ulrike Langematz, Markus Kunze, Kirstin Krueger, Karin Labitzke, Free University of Berlin, Berlin, Germany;
Gregory L. Roff, Bureau of Meteorology, Melbourne, Australia.

Source: Journal of Geophysical Research-Atmospheres (JGR-D) paper: 10.1029/2002JD002069, 2003

A new study supports ideas that the release of frozen methane hydrates from the ocean floor heated the Earth's temperatures up to 7 degrees Celsius [10 degrees Fahrenheit] during the Paleocene/Eocene Thermal Maximum period, approximately 55 million years ago. Schmidt and Shindell present results from a
paleoclimate simulations of atmospheric chemistry and conclude that the short-lived global climate change could have been induced by methane release into the atmosphere. Previous research had indicated that elevated methane emissions were likely, but there has been some speculation about whether the higher ocean temperatures led to the release of frozen methane hydrates or whether the hydrates raised carbon dioxide levels during this period and led to a rapid warming. The authors' model shows that the released hydrates led to heightened atmospheric methane concentrations and the sudden warming.

Title: Atmospheric composition, radiative forcing and climate change as a consequence of a massive methane release from gas hydrates

Authors:
Gavin A. Schmidt, Drew T. Shindell, NASA Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University, New York, New York.

Source: Paleoceanography (PA) paper: 10.1029/2002PA000757, 2003

A theoretical design for a small, lightweight satellite weather radar could provide more accurate snow and rain estimates with less expensive launch costs. Meneghini et al. propose a new concept for a Doppler radar whose dual frequencies are closely spaced, eliminating the need for a larger, more complex radar with separate antennas and transmitters. The signal returns from dual frequencies allow researchers to estimate the median size and concentration of precipitation, like rain and snow, providing a better understanding of the development and evolution of storms. The authors' new design uses frequencies separated by 7 to 10 percent, rather than the much larger frequency differences that have been proposed for satellite-based weather radars. They conclude that the new radar instrument, when flown with traditional (passive) remote sensing equipment, could improve the accuracy of current satellite-based rainfall estimates.

Title: Differential-frequency Doppler weather radar: Theory and experiment

Authors:
Robert Meneghini, S. W. Bidwell, R. Rincon, G. M. Heymsfield, NASA Goddard Space Flight Center, Greenbelt, Maryland;
L. Liao, Caelum Research Corp., Rockville, Maryland.

Source: Radio Science (RS) paper: 10.1029/2002RS002656, 2003

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