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Main Page | Articles (1)

Oceans

Overview

The earth’s atmosphere, climate and weather, is closely interlinked with the oceans. There are over 50 named ocean currents that transfer heat and cold from one area to another. Currents can be shallow and warm or deep and cold. Convective overturning occurs in places when the dense surface water mixes downward. The Gulf Stream and the Great Conveyor Belt are largely responsible for heat transfer between the southern and northern Atlantic hemispheres, and control the moderate climate of Europe. This current has been the focus of the cause of abrupt climate changes in the past.

El Niño and La Niña are two opposite weather patterns that occur in the central tropical Pacific Ocean. El Niños are associated with warming trends and La Niñas with cooling trends. The patterns are not that predictable, generally occurring every 2 to 7 years and lasting 1 to 2 years. Scientists sometimes describe “El Nino like conditions” in the Atlantic to explain hurricane intensities and frequencies in that area.

Pacific Decadal Oscillations or PDOs are El Niño like patterns of the Pacific climate, except that they last 20 to 30 years as opposed to the 1 to 2 year cycles of El Niños. In 1977, a major PDO (also known as the Great Pacific Climate Shift) occurred resulting in warmer surface temperatures along the west coast of North America. The effect has been to push the jet stream across North America further north. Scientists are debating if a shift back to a cooler cycle has occurred yet.

Atlantic Multidecadal Oscillations (AMOs) are similar to PDOs except that they occur in the Atlantic in the area between the equator and Greenland. The warming cycles are considered to be responsible for past long droughts in the Midwest and Southwest areas of North America.

Arctic Oscillations are reversals in decade long migration patterns of warmer and more saline ocean currents in the Arctic Ocean. This natural cycle is believed to have amplified the natural warming trend from the late 1970s through at least the 1990s in the Arctic region.

The National Academies
Woods Hole Oceanographic Institute
NOAA Physical Oceanography

Supporting Viewpoints

Those with supporting views believe that ocean warming is caused by human generated global warming, and that warmer oceans have an impact on weather patterns and events. For example, the melting of Greenland glaciers due to human induced global warming introduces more fresh water into the ocean current system and can cause major currents like the Great Conveyer Belt to shut down as they have many times in the past. This could cause a major cooling event in Europe that would last several years.

Also, according to some scientists, the current rate of melting of the massive ice sheets in Greenland and Antarctica and mountain glaciers could cause sea levels to rise by 2 to 6 feet in this century. To put it in perspective, the water volume contained in Greenland’s ice alone is roughly the same as the volume of water in the Gulf of Mexico.

Supporting Websites
Science Daily
Oceana
Union of Concerned Scientists

Opposing Viewpoints

People with opposing views on global warming disagree that any small increase in ocean temperatures can be linked to major weather events. Such findings often minimize the more profound effects and history of natural cycles such as El Niños, La Niñas, PDOs, AMOs, and Arctic Oscillations. Modeling these effects along with those of human induced greenhouse gas emissions can be extremely complex and subject to a wide range of uncertainty.

For example, the melting of glaciers in Montana’s Glacier National Park and Alaska could in large part be attributed to the warm cycle of the Pacific Decadal Oscillation that began in 1977and the Arctic Oscillation that began about the same time. If these long term oscillations have recently reversed as some scientists believe, then we should start seeing a slowing of the rate of glacier melt in this region in the next few years.

On a much longer time scale, ice cores from Greenland and Antarctica have shown large variability and sometimes abrupt changes in temperatures over the past 110,000 years. Greenland’s temperatures have cycled up and down over time. Contradicting current reports on glacial melting, an article in the Heartland Institute website states that “the last two decades of the twentieth century were the coldest decades for Greenland since the 1910s.” A 2008 paper in ICECAP states that “the ice between Canada and southwestern Greenland has reached its highest level in 15 years”. Temperatures of minus 30 degrees Celsius have expanded the ice mass to its most southern extent in 15 years.

Opposing Websites
Heartland Institute
ICECAP, International Climate and Environmental Change Assessment Project
Reason Online
Weather Underground: Abrupt Climate Change
World Climate Report


Oceans Content

Habitats
Article:
The world's rubbish dump: a garbage tip that stretches from Hawaii to Japan - K. Marks, D. Howden
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Published:2/5/2008
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Submitted by:Frank K 210 days ago
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Categories: Habitats & Oceans
Article Details:   A "plastic soup" of waste floating in the Pacific Ocean is growing at an alarming rate and now covers an area twice the size of the continental United States. The vast expanse of debris – in effect the world's largest rubbish dump – is held in place by swirling underwater currents. This drifting "soup" stretches from about 500 nautical miles off the Californian coast, across the northern Pacific, past Hawaii and almost as far as Japan.



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