WES WEEK ELEVEN: 26-30 November 2001

• Glacial meltwater could have affected Gulf Stream -- A team of scientists has recently released a report that suggests that fresh water melting off the large continental glaciers at the end of the most recent Pleistocene glaciation (approximately 11,500-13,000 years ago) and entering the North Atlantic Ocean could have caused a major change in the deep-water circulation system. They propose that this change, which could have persisted for several centuries, could have weakened the Gulf Stream to the point where little heat would have been transported northward, thereby resulting in cooler climatic conditions in northwest Europe. [NASA GSFC]
• Results of an Arctic Ocean cruise released -- Scientists participating in a cruise aboard the icebreaker USCGC Healy discovered evidence of hydrothermal activity with possible underwater vents along the submerged Gakkel Ridge in the Arctic Ocean. A middle school classroom teacher also participated on last summer's cruise. [EurekAlert!]
• Forest management may affect atmospheric carbon dioxide increases -- A researcher at the University of Wisconsin-Madison reported that more effective management of forests could sequester more carbon compounds and reduce the observed increases in the atmospheric carbon dioxide. The increases in carbon dioxide are often linked to increases in global temperature and the height of sea level. [EurekAlert!]
• Flooding in the Canary Islands caused deaths -- Heavy rains in Spain's Canary Islands caused flash flooding last Tuesday (the 20^th), which caused the deaths of three German tourists trapped in a ravine in a national park on the islands. As many as 142 people had to be rescued from the high waters. [CNN]
• Rains help in fire-fighting efforts -- Little rain has fallen across the Southeast this autumn resulting in increased susceptibility of the region to wildfires. However some recent rains have helped in the fire-fighting efforts in Kentucky and Tennessee. [ENN]
• Earth diary -- A summary of the week's major environmental events on Planet Earth. [CNN]

Concept of the Week: Desertification

Desertification is one of the world's most pressing environmental issues, threatening the existence of more than a billion people who depend on the land for survival. In 1992, the United Nation's Conference on Environment and Development defined desertification as "land degradation in arid, semi-arid, and dry sub-humid areas resulting from various factors, including climate variations and human activities." Through desertification, arable land is transformed into desert-like land, greatly reducing or eliminating the land's capacity to produce food. Desertification's impact on people dependent on subsistence farming and herding is food insecurity and often their only option to avoid famine is migration to urban areas.

According to U.N. estimates, desertification affects about 130 million hectares (320 million acres) of land worldwide, equivalent to the areas of France, Italy, and Spain combined. Portions of some 110 nations are impacted, including parts of the North American Great Plains, the Pampas of South America, the steppes of Asia, the "outback" of Australia, and the edges of the Mediterranean. But by far the most widespread and severe impact is in Africa where two-thirds of the continent's land area is desert or dry land. Almost three-quarters of Africa's dry-land agricultural area is degraded to some extent. Desertification is a very serious problem in Sub-Saharan Africa with its considerable year-to-year variability in seasonal rainfall and frequency of long-term drought (described on pages 83-84 of the WES Textbook).

The systems approach is valuable in understanding desertification in that the process involves interactions of climate, Earth's land surface, the water cycle, and human activity. Desertification of dry lands accelerates during prolonged drought. Climate change can alter the frequency and intensity of drought and thereby contribute to soil desiccation. Although climate change may play an important role in desertification, a key factor is human mismanagement of the soil resource. Poverty and subsistence agriculture drives people to over-cultivate the land, quickly exhausting the soil's fertility. Overgrazing by livestock and deforestation exacerbate an already bad situation by removing the protective vegetative cover and exposing the topsoil to erosion by wind and running water. Winds can transport fine topsoil thousands of kilometers and sandstorms strip the leaves from plants and bury crops under dunes.

Land mismanagement also impacts the local climate and water budget, speeding up desertification. Without a vegetative cover, the soil surface temperature rises, accelerating evaporation of water, depletion of soil moisture, and build up of salts in the soil. Less soil moisture means that more of the available heat is used for raising the air temperature through conduction and convection (i.e., sensible heating). In this way heat stress combines with moisture stress to cut into crop yields.

Concept of the Week: Questions

1. Through desertification, crop productivity [(declines) (increases)].
2. Human mismanagement of the soil resource [(is) (is not)] a key factor in desertification.

• 26 November 1888...A late season hurricane brushed the East Coast with heavy rain and gale force winds. The hurricane passed inside Nantucket and over Cape Cod, then crossed Nova Scotia. (David Ludlum)
• 26-28 November 1898...The "Portland" storm raged across New England producing gale force winds along the coast and heavy snow inland. A foot of snow blanketed Boston, MA, and 27 inches fell at New London, CT. Winds at Boston gusted to 72 mph, and wind gusts to 98 mph were estimated at Block Island, RI. A passenger ship, the S.S. Portland, sank off Cape Cod with the loss of all 191 persons aboard, and Boston Harbor was filled with wrecked ships. The storm wrecked 56 vessels resulting in a total of 456 casualties. (26th- 28th) (David Ludlum) (The Weather Channel)
• 27-28 November 1905... Heavy snow and wind blasted the western Great Lakes with as much as seven inches of snow in northwestern Wisconsin and sustained winds of 42 mph were recorded at Duluth, MN for 29 straight hours and 65 mph winds for 13 continuous hours. Severe drifting resulted. Eighteen ships were destroyed or disabled on Lake Superior. The ship Mataafa was grounded and broke in two in Duluth harbor. Nine of the fifteen crew of the Mataafa froze to death despite running aground within 100 yards of the shore. (Accord Weather Calendar)
• 27-28 November 1912...Snowfall is a rare event for Florida. The record earliest snowfall for Florida, and the only November snowfall fell during the night across part of the interior counties in the far northwest (Madison to Gadsden) bordering Georgia. Up to 0.5 inches of snow was reported at Mt. Pleasant. (Accord Weather Calendar)
• 27 November 1930...A terrific sandstorm in Morocco supplied the dust for the "mud rain" on the following day that fell from northern France to southern England. In Belgium a number of people were asphyxiated near Liege due to poor air quality. (Accord Weather Calendar)
• 28 November 1921...New England was in the midst of a four day icestorm, their worst of record. Ice was more than three inches thick in many places following the storm, and property damage was in the millions of dollars. Northern New England received heavy snow with more than two feet reported in some areas. Overnight freezing rains continued through the day at Worcester, MA while the wind increased to a gale. Streets become impassable even on foot, and whole towns were plunged into darkness without communication. The storm caused 20 million dollars damage to power lines, telephone lines and trees. (David Ludlum)
• 28 November 1960...A severe storm produced waves 20 to 40 feet high on Lake Superior. Duluth, MN was buried under a foot of snow, and clocked wind gusts to 73 mph. The northern shore of Lake Superior was flooded, and property along the shore was battered. Thousands of cords of pulpwood were washed into Lake Superior, and up to three feet of water flooded the main street of Grand Marais. Thunder accompanied the "nor'easter". (David Ludlum) (The Weather Channel)
• 28-29 November 1995...Rivers in western Washington State experienced near-record flooding. In Snohomish County, 2000 students could not reach school because of flooded roads. In Duvall and Carnation, flooded roads stranded 15,000 people. (Accord Weather Calendar)
• 30 November 1957...Lee slope winds enhanced by Hurricane Nina gusted to 82 mph at Honolulu, HI, a record wind gust for that location. Wainiha, on the island of Kauai, was deluged with 20.42 inches of rain, and 35-foot waves pounded some Kauai beaches, even though the eye of the hurricane was never within 120 miles of the islands. (30th-1st) (The Weather Channel)

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Prepared by AMS WES Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
ã Copyright, 2001, The American Meteorological Society.