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nuclear Freeze

During the Cold War, several periods of protest against nuclear weapons took place in the United States. By far the largest protest campaign involved the nuclear freeze movement. This ...

Sea Ice

Sea Ice   Reference library

Encyclopedia of Global Change

Reference type:
Subject Reference
Current Version:
2005
Subject:
Science and technology, Environmental Science, Social sciences, Environment
Length:
4,223 words
Illustration(s):
5

...may still be close to 4°C. Thus a lake can freeze early while considerable heat remains at depth. When the salinity exceeds 24.7 psu (practical salinity units, equivalent to parts per thousand), there is no temperature of maximum density, and convection continues down to the freezing point (−1.8°C for typical sea water). The whole upper water column, down to the level of a density gradient (the pycnocline), has to reach the freezing point before ice can form at the surface. A sea therefore takes longer to freeze over than a lake. A salinity of 24.7 psu...

North Pole

North Pole   Reference library

Encyclopedia of Climate and Weather (2 ed.)

Reference type:
Subject Reference
Current Version:
2011

...of sea ice at 90° north latitude: In 1991 it was barely 1.2 meters thick and 2 diesel-powered ice breakers were able to reach the pole (the first ones to do so), while in 1992 the depth exceeded 3.0 meters and it took much work by a nuclear-powered ice breaker to reach the same position. In 2003 a nuclear ice breaker was unable to reach the North Pole in the time available, as 3-meter-thick ice was encountered at only 84°N. There is much conjecture as to whether global warming may affect sea-ice thickness and permit easier navigational access...

Atmosphere

Atmosphere   Reference library

Encyclopedia of Climate and Weather (2 ed.)

Reference type:
Subject Reference
Current Version:
2011
Subject:
Science and technology, Earth Sciences and Geography, Social sciences, Environment
Length:
4,482 words
Illustration(s):
2

...system. (This prediction is somewhat counterintuitive, because the Sun is gradually consuming its nuclear fuel as it converts hydrogen to helium; however, it is a standard feature of virtually all solar evolution models.) If the atmospheric CO 2 concentration on the early Earth were the same as today, and if no other greenhouse gases besides water vapor were present in significant amounts, this decrease in solar luminosity would have caused the oceans to freeze over completely. The geologic record, however, indicates that liquid water has been present on...

Human Impacts

Human Impacts   Reference library

Encyclopedia of Global Change

Reference type:
Subject Reference
Current Version:
2005

...in species distributions, climate warming may lead to reduced biodiversity in streams as temperatures in the headwaters and downstream reaches become less variable. Similar effects are predicted for temperate lakes, where the thermal environment is determined by the timing of freeze and thaw, the degree of stratification, and the depth of the thermocline. Some species will be at risk of extinction because of changes in their thermal niches or through competition from species that were previously excluded (Graves and Reavey, 1996). Wetlands are also sensitive...

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