Snow-free regions on rise and Alaskan Arctic growing greener

Increasing Snow-free regions and progression of trees in Alaskan Arctic will lead to drastic change in climate on earth

According to study published in issue of science express, gradually increasing Snow-free Tundra regions of Alaska and progression of shurbs and trees in northen Alaska region will contribute to the cycle of more warmer and longer summers in Artic.

Scale of the atmospheric heating due to the longer summers is equivalent to the results of doubling of carbon dioxide in the atmosphere. Atmospheric heating due to such cycles can bring drastic changes in the climate on earth.

“We suggest that a noticeable summer warming trend in Alaska is best explained by a lengthening of the snow-free season there,” said Howard E. Epstein, an associate professor of environmental sciences at the University of Virginia and a co-author of the new study. The scientists determined that the increasing summer temperatures in northern Alaska could not be attributed to regional atmospheric circulation patterns or to a reduction in sea ice in the summer or to an increase in cloud cover. The observed summer temperature increases are likely related to a global warming trend that has led to a longer snow-free season and an increase in the extent of woody vegetation. Both of these changes increase the amount of solar radiation that goes into heating rather than being reflected back to the atmosphere.

Epstein said that since the early 1960s the spring thaw in Alaska’s tundra country is arriving an average of 2.3 days earlier each decade. As a result, plants in the region now “leaf out” about 2.7 days earlier than in previous decades. Likewise, the first freeze each year is arriving slightly later, allowing plants to extend their growing season. The longer growing season is allowing shrubs and trees to slowly migrate northward. The increasing woody vegetation is further warming the near-surface atmosphere by absorbing rather than reflecting incoming solar radiation.

“The vegetation change is pretty dramatic,” Epstein said. “The tundra is getting greener, and there is a noticeable increase in shrubs. This is observable from satellite data and by observations on the ground. Native American people in the region and nearby areas also have noted the changes in weather and vegetation.”

Because there is a shorter period of snow on the ground, solar radiation is absorbed by the land surface more readily and contributes to heating, thus accelerating the melting of snow and allowing for more plant growth. Over time, as the permafrost begins to melt, ancient organic matter that has been frozen for thousands of years is exposed, potentially adding more carbon dioxide to the atmosphere.

“We know that certain parts of the Arctic are warming pretty substantially and more so than in other regions around the globe,” Epstein said. “This is significant because conditions in the Arctic affect global atmosphere conditions. The Arctic is dominated by snow and ice, and if this condition were to change, even subtly, there is potential for further change to the global climate.”

Investigators from several universities and other institutions conducted the research, which was funded by the National Science Foundation through its Arctic Transitions of the Land/Atmosphere System project.

Original news can be found here