Southern climates shifting northward, says study

An international group of scientists have been studying vegetation changes in the North, and found that, over the past 30 years, the seasonal patterns of plant growth at northern latitudes is becoming more and more like the seasonal patterns seen further to the south.

In a NASA-funded study, involving scientists from 17 institutions in 7 different countries, the researchers set a 'base-line' of temperature and vegetation patterns — their 'seasonality', or seasonal variation — from the early 1980s, and then used satellite data to track how those patterns have slowly migrated to the north since then.

[ Related: Study finds climate change making Arctic more like south ]

The researchers found that, just in the last 30 years, the growth of plants has shifted northward, such that the vegetation seen near the Arctic Circle — roughly through central Yukon and Northwest Territories, and southern Nunavut — now more closely resembles the vegetation normally found in northern regions of B.C., Alberta, Saskatchewan, Manitoba and Quebec, some 850 kilometres to the south.

"The reduction of vegetation seasonality, resulting in increased greenness in the Arctic, is visible on the ground as an increasing abundance of tall shrubs and tree incursions in several locations all over the circumpolar Arctic," says study co-author Prof. Terry Callaghan, an Arctic ecologist at the University of Sheffield, UK.

"The amplified warming in the circumpolar area — roughly above the Canada-USA border — is reducing temperature seasonality over time because the colder seasons are warming more rapidly than the summer," says lead co-author Liang Xu, a doctoral student at Boston University's Climate and Vegetation Research Group.

"As a result of the enhanced warming over a longer ground-thaw season, the total amount of heat available for plant growth in these northern latitudes is increasing. This created, during the past 30 years, large patches of vigorously productive vegetation, totaling more than a third of the northern landscape — over 9 million km², which is roughly about the area of the USA — resembling the vegetation that occurs further to the south," says Dr. Compton Tucker, Senior Research Scientist in the Earth Sciences Division at NASA's Goddard Space Flight Center.

[ More Geekquinox: ‘Irreversible’ thaw in store for Canada’s glaciers ]

This may seem like all is fine, as a longer growing season could certainly only be good news, but with the extended thaw for these northern regions comes other problems, including permafrost thaw causing the release of tons more stored carbon and methane, thus enhancing the greenhouse effect and climate change even more, and adverse effects on wildlife.

"The way of life of many organisms on Earth is tightly linked to seasonal changes in temperature and availability of food, and all food on land comes first from plants," says Dr. Scott Goetz, Deputy Director and Senior Scientist of the Woods Hole Research Center, in Falmouth, MA. "Think of migration of birds to the Arctic in the summer and hibernation of bears in the winter: Any significant alterations to temperature and vegetation seasonality are likely to impact life not only in the north but elsewhere in ways that we do not yet know."

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