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Patterns of Climate Change (continued)

Diminishing Snowpack

Snowpack is diminishing worldwide endangering water supplies for irrigation as well as for major population centers. Using data collected over the past 50 years, scientists confirmed that the mountains across the Western United States are getting significantly more rain and less snow, that the snowpack is breaking up faster, and that more rivers are running dry by summer. Tim Barnett of the University of California at San Diego reported in the Journal Science that these changes were not due to natural variations in climate. "We have found very clearly that global warming has done it, that it is the mechanism that explains the change, and that things will be getting worse."

The mountain snowpack is crucial to many in the West and Southwest who depend on its springtime melt for power, irrigation, and drinking water. When the snow fields melt earlier and more suddenly, downstream dams are able to capture less of the water and must release more of it in springtime torrents that flow on to the ocean. About 60% of the summer water supply for the State of California is derived from the snow melt in the Sierras. This summer melt has been reduced by the diminished snowpack.

Lake Mead, which stores water and supplies hydroelectric power for Southern Californian, Nevada and Arizona, is down 50% from normal and has a 50% likelihood of being dry by 2020. The water level at Lake Mead is monitored regularly by government surveyors and is posted on a chart on the web by a local citizen.

Two climate change effects work together to diminish this summer time flow from snowpack. First the snow melts earlier in the season and more of it comes down as rainfall instead of snow. Though spring flooding may be greater, the summer time reservoirs of snow are diminished and eventually lost. Second the evaporation rates are greater in a warming climate. This reduces the amount of moisture retained both in the snowpack as well as in the soils. The effective irrigation of such water starved agricultural regions becomes increasingly problematic.

Vanishing Glaciers

Time lapse photography (video) is now documenting the monumental retreat of glaciers in Alaska, Iceland and Greenland. The World Wildlife Federation completed a detailed report discussing the global impact of this decline.

Briefly, many rivers are fed by glacial melt. As glaciers vanish (video) throughout the world, these rivers will be greatly altered or even disappear. The headwaters of the great Ganges in India is fed by glacial melt from the Himalayas. The Gangotri glacier, which provides up to 70% of the water to the Ganges during the summer months, is in severe retreat. Regions in China face similar destabilization of glacier fed water supplies to large agricultural regions as well as major population centers.

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Premature Collapse of Arctic Summer Ice & Positive Feedback Effects

Arctic sea ice (video) is thinner and there is less of it.

In the summer of 2007 the world received an alarming wake-up call when over 23% more ice than ever before melted from the Arctic Ice Sheet. Scientists had not anticipated this premature collapse of the Arctic ice. It brought the emergency of global warming to the forefront of scientific concern.

The melting of the Arctic sea ice in the summer will not raise sea levels as this ice is already floating. (Here is a direct link to the chart of the status Arctic sea ice extent which is updated daily.) However, the white Arctic ice acts like a mirror, reflecting and bouncing light from the sun back into space. By contrast, the dark sea waters, that are replacing this ice, absorb heat from the sun's rays throughout the long days of the arctic summer. This continent sized absorption of heat from the sun will significantly contribute to global average temperature increases, amplifying the effects of the greenhouse gases in the atmosphere. This absorption of sunlight as heat will raise the earths temperature a projected .3 degrees C and push us perilously close to "dangerous" levels of climate change.

The premature collapse or the Arctic summer ice meant that the consequences of increased levels of atmospheric CO2 were not centuries or many decades away, but in our immediate future. The alarm had been sounded in the quiet melting of the ice at the top of the earth.

As this meltdown of ice at the north pole is 40-70 years ahead of the predicted schedule, you might wonder what this portends for other ice sheets.

Rising Sea Levels and Coastal Flooding

Sea Levels are slowly rising now, due to the following:

  • The worldwide melting of mountain glaciers
  • Thermal expansions of the oceans: As water gets warmer, it expands. The heat near the surface of the oceans is increasing. Sea levels are rising incrementally due to this thermal expansion.
  • The Greenland Ice Sheet is melting. The recent animation of Greenland's shrinking ice sheet visualizes how rapidly the ice is changing. Greenland's glaciers are flowing into the sea at ever increasing rates. Were all of Greenland to melt, sea levels could rise as much as 6.5 meters or 20 feet.
  • Glaciologists consider West Antarctica the greatest source of uncertainty in sea level projections. The base of the 3000 meter thick West Antarctic Ice Sheet, unlike the much larger East Antarctic Ice Sheet, lies below sea level. This huge amount of ice is grounded on the ocean floor. It is not floating. This grounded ice of Western Antarctica has the potential to change rapidly as it can be melted quickly by warming seas from below, destabilize and fail mechanically from above as it warms. This unstable ice structure has the potential to raise sea levels abruptly.

Coastal regions that are at or near sea level (video), such as Florida and major coastal cities (video), such as New Orleans and New York, face ongoing encroachment of their shore lines. As the century progresses, coastlines will face greater and greater threats from storm surges as the oceans slowly invade inward and encompass protective wetlands. Low lying port areas and beaches will disappear. Unstoppable high tides will creep farther and farther inland and eventually never go out.

Explore how rising sea levels impact coastlines with this google-map tool.

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