{"id":8720,"date":"2013-03-14T10:49:10","date_gmt":"2013-03-14T14:49:10","guid":{"rendered":"http:\/\/www.bu.edu\/cas\/?p=8720"},"modified":"2016-11-08T10:19:31","modified_gmt":"2016-11-08T15:19:31","slug":"bu-led-study-shows-dramatic-arctic-climate-change","status":"publish","type":"post","link":"https:\/\/www.bu.edu\/cas\/bu-led-study-shows-dramatic-arctic-climate-change\/","title":{"rendered":"BU-Led Study Shows Dramatic Arctic Climate Change"},"content":{"rendered":"

An international team of 21 authors from 17 institutions in seven countries has just published a study in the journal Natural Climate Change showing that, as the cover of snow and ice in the northern latitudes has diminished in recent years, the temperature over the northern land mass has increased at different rates during the four seasons, causing a reduction in temperature and vegetation seasonality in this area. In other words, the temperature and vegetation at northern latitudes increasingly resembles those found several degrees of latitude farther south as recently as 30 years ago. The study, titled \u201cTemperature and vegetation seasonality diminishment over northern lands\u201d (DOI: 10.1038\/NCLIMATE1836), can be downloaded here:http:\/\/dx.doi.org\/<\/a>.<\/p>\n

The NASA-funded study, based on newly improved ground and satellite data sets, examines critically the relationship between changes in temperature and vegetation productivity in northern latitudes.<\/p>\n

On the amplified greenhouse effect, Ranga Myneni, professor of earth and environment at Boston University and lead co-author, says, \u201cA greenhouse effect initiated by increased atmospheric concentration of heat-trapping gasses\u2014such as water vapor, carbon dioxide and methane\u2014causes the Earth\u2019s surface and nearby air to warm. The warming reduces the extent of polar sea ice and snow cover on the large land mass that surrounds the Arctic ocean, thereby increasing the amount of solar energy absorbed by the no longer energy-reflecting surface. This sets in motion a cycle of positive reinforcement between warming and loss of sea ice and snow cover, thus amplifying the base greenhouse effect.\u201d<\/p>\n

\u201cThe 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,\u201d says Liang Xu, a Boston University doctoral student and lead co-author of the study.<\/p>\n

\u201cAs 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\u2014over 9 million km2, which is roughly about the area of the USA\u2014 resembling the vegetation that occurs further to the south,\u201d says Dr. Compton Tucker, Senior Scientist, NASA\u2019s Goddard Space Flight Center, Greenbelt, Maryland.<\/p>\n

The authors measured seasonality changes using latitude as a yardstick. They first defined reference latitudinal profiles for the quantities being observed and then quantified changes in them over time as shifts along these profiles.<\/p>\n

\u201cArctic plant growth during the early-1980s reference period equaled that of lands north of 64 degrees north. Today, just 30 years later, it equals that of lands above 57 degrees north\u2014a reduction in vegetation seasonality of about seven degrees south in latitude,\u201d says co-author Prof. Terry Chapin, Professor Emeritus, University of Alaska, Fairbanks. \u201cThis manner of analyses suggested a decline in temperature and vegetation seasonality of about four to seven degrees of latitude during the past 30 years,\u201d says co-author Eugenie Euskirchen, Research Professor, University of Alaska, Fairbanks.<\/p>\n

\u201cThe 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,\u201d says co-author Terry Callaghan, Professor, Royal Swedish Academy of Sciences and the University of Sheffield, UK. He notes that the greening in the adjacent Boreal areas is much less conspicuous in North America than in Eurasia.<\/p>\n

A key finding of this study is an accelerating greening rate in the Arctic and a decelerating rate in the boreal region, despite a nearly constant rate of temperature seasonality diminishment in these regions over the past 30 years. \u201cThis may portend a decoupling between growing season warmth and vegetation productivity in some parts of the North as the ramifications of amplified greenhouse effect\u2014including permafrost thawing, frequent forest fires, outbreak of pest infestations, and summertime droughts\u2014come in to play,\u201d says co-author Hans T\u00f8mmervik, Senior Researcher, Norwegian Institute for Nature Research, Troms\u00f8, Norway.<\/p>\n

According to the authors, the future does indeed look troubling: Based on analysis of 17 state-of-the-art climate model simulations, diminishment of temperature seasonality in these regions could be more than 20 degrees in latitude by the end of this century relative to the 1951-1980 reference period. The projected temperature seasonality decline by these models for the 2001-2010 decade is actually less than the observed decline. \u201cSince we don\u2019t know the actual trajectory of atmospheric concentration of various agents capable of forcing a change in climate, long-term projections should be interpreted cautiously,\u201d says co-author Bruce Anderson, Professor of Earth and Environment at Boston University.<\/p>\n

\u201cThese changes will affect local residents through changes in provisioning ecosystem services such as timber and traditional foods,\u201d says Research Professor Bruce Forbes, University of Lapland, Rovaniemi, Finland. They will also impact the global community through changes in regulatory ecosystem services relating to emissions of greenhouse gases. \u201cThe soils in the northern land mass potentially can release significant amounts of greenhouse gases which are currently locked up in the permanently frozen ground. Any large-scale deep-thawing of these soils has the potential to further amplify the greenhouse effect,\u201d says co-author Philippe Ciais, Associate Director, Laboratory of Climate and Environmental Science, Paris, France.<\/p>\n

\u201cThe 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,\u201d says Dr. Scott Goetz, Deputy Director and Senior Scientist, Woods Hole Research Center, Falmouth, USA. \u201cThink 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.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

Temperature and vegetation in northern latitudes resembles that found much further south just 30 years ago.<\/p>\n","protected":false},"author":3521,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[4,195,5],"tags":[219],"_links":{"self":[{"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/posts\/8720"}],"collection":[{"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/users\/3521"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/comments?post=8720"}],"version-history":[{"count":5,"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/posts\/8720\/revisions"}],"predecessor-version":[{"id":8744,"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/posts\/8720\/revisions\/8744"}],"wp:attachment":[{"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/media?parent=8720"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/categories?post=8720"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bu.edu\/cas\/wp-json\/wp\/v2\/tags?post=8720"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}