Wang L.,Environment Canada |
Wolken G.J.,354 College Rd |
Wolken G.J.,University of Alberta |
Sharp M.J.,University of Alberta |
And 5 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2011
An integrated pan-Arctic melt onset data set is generated for the first time by combining estimates derived from active and passive microwave satellite data using algorithms developed for the northern high-latitude land surface, ice caps, large lakes, and sea ice. The data set yields new insights into the spatial and temporal patterns of mean melt onset date (MMOD) and the associated geographic and topographic controls. For example, in the terrestrial Arctic, tree fraction and latitude explain more than 60% of the variance in MMOD, with the former exerting a stronger influence on MMOD than the latter. Elevation is also found to be an important factor controlling MMOD, with most of the Arctic exhibiting significant positive relationships between MMOD and elevation, with a mean value of 24.5 m d-1. Melt onset progresses fastest over land areas of uniform cover or elevation (40-80 km d-1) or both and slows down in mountainous areas, on ice caps, and in the forest-tundra ecotones. Over sea ice, melt onset advances very slowly in the marginal seas, while in the central Arctic the rate of advance can exceed 100 km d-1. Comparison of the observed MMOD with simulated values from the third version of the Canadian Coupled Global Climate Model showed good agreement over land areas but weaker agreement over sea ice, particularly in the central Arctic, where simulated MMOD is about 2-3 weeks later than observed because of a cold bias in simulated surface air temperatures over sea ice. Copyright 2011 by the American Geophysical Union.
Sharp M.,University of Alberta |
Burgess D.O.,Geological Survey of Canada |
Cogley J.G.,Trent University |
Ecclestone M.,Trent University |
And 2 more authors.
Geophysical Research Letters | Year: 2011
Canada's Queen Elizabeth Islands contain ∼14% of Earth's glacier and ice cap area. Snow accumulation on these glaciers is low and varies little from year to year. Changes in their surface mass balance are driven largely by changes in summer air temperatures, surface melting and runoff. Relative to 2000-2004, strong summer warming since 2005 (1.1 to 1.6C at 700 hPa) has increased summer mean ice surface temperatures and melt season length on the major ice caps in this region by 0.8 to 2.2C and 4.7 to 11.9 d respectively. 30-48% of the total mass lost from 4 monitored glaciers since 1963 has occurred since 2005. The mean rate of mass loss from these 4 glaciers between 2005 and 2009 (-493 kg m-2 a-1) was nearly 5 times greater than the 1963-2004 average. In 2007 and 2008, it was 7 times greater (-698 kg m -2 a-1). These changes are associated with a summer atmospheric circulation configuration that favors strong heat advection into the Queen Elizabeth Islands from the northwest Atlantic, where sea surface temperatures have been anomalously high. Copyright © 2011 by the American Geophysical Union.