September 2010, Vol. 22, No.9

Waterline

Michigan researchers reveal new method to monitor permafrost thawing

Because of the difficulty monitoring thawing of permafrost — soil that remains at or below the freezing point for at least 2-year-long periods — University of Michigan (Ann Arbor) researchers conducted a study to find a way to help assess the extent of the problem, according to a University of Michigan news release.

The research found that soil chemistry of permafrost levels differed from the overlying layer that thaws every summer, and newly thawing permafrost reacts strongly with water that it is encountering for the first time in thousands of years. Researchers looked into the possibilities of identifying these chemical signatures in local streams, the news release says.

After analyzing 11 years of streamwater samples collected from Toolik Lake in northern Alaska, researchers found significant changes from year to year that could predict increasing thaw depth. While the new method can’t reveal how much thawing is occurring, it can be a useful adjunct to current methods, the news release says.

Study identifies many reasons for 2009 floods in Atlanta

Record rainfall in Atlanta during September 2009 flooded much of the city and surrounding areas, exceeding flood levels expected only once every 500 years in some areas, according to a University of Georgia (Athens) news release.

A team of climatologists, meteorologist, geologists, and hydrologists led by the University of Georgia have determined that a convergence of record-setting events caused the floods.

Prior to the rainfall, a low-pressure system stalled over parts of Arkansas, Louisiana, and Texas, pulling moisture from the Gulf of Mexico. In addition, remnants of two tropical storms added to the wet air over the Southeast, and atmospheric instability in the mountains northwest and north of Atlanta produced repeated and heavy rainfall.

But researchers say the spark that triggered the floods may have been the amount of concrete and pavement in Atlanta’s metro area, preventing water from soaking into the ground and overfilling sewers and drainage areas, the news release says. Marshall Shepherd, lead researcher of the study, will continue looking into flooding and the possibility that large cities may alter storms through heat-island, convergence, and pollution effects, the news release says.

Size of oceans identified by scientists

Woods Hole Oceanographic Institution (WHOI;Falmouth, Mass.) scientists are tackling a substantial task: quantifying the amount of water in Earth’s oceans. Scientists are now able to discern the mean depth — 3682.2 m — and volume — 1.332 billion km3 — of the oceans.

The scientists used satellite measurements to create a map of the ocean surface and use this information to determine what lies on the floor below. The resulting depth and volume values are smaller than recent estimates because of the increasing ability to locate undersea mountain ranges and other formations, which are more abundant than originally thought, according to a WHOI news release.

However, satellite imagery is not perfect, and the scientists were only able to identify areas affected by larger mountains. The scientists noted the need for additional ship-based measurements to augment satellite data, the news release says. To date, only about 10% of the ocean floor has been mapped by ship.

New biocontrol for invasive plant

As an invasive aquatic plant, the water hyacinth, which is native to South America, causes many problems in North America, including reducing navigability of waterways, harming water infrastructure, and reducing oxygen levels in water. But now, the U.S. Department of Agriculture’s Agricultural Research Service (ARS) has devised a new strategy to control this free-floating plant’s proliferation, according to an ARS news release.

ARS scientists worked in Argentina to test a new biocontrol for the water hyacinth: the plant-hopping insect Megamelus scutellaris. Nymphs and adults of the small insect, which also is native to South America, feed on the plant’s sap. Because the insect’s population increases rapidly, scientists hope that it can quickly affect the water hyacinth population. Current herbicide programs interfere with biocontrol agents in place now, but because the insect is mobile, scientists believe it will have a better survival rate, the news release says.

Researchers collected adult insects from Argentina in April 2006 and brought them to a quarantine facility in Fort Lauderdale, Fla., where extensive host-range studies were conducted. The studies found that the insect is host-specific and does not pose a threat to native or other economically important species, the news release says.

 

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