Snow melt in the Alaska Range The Alaska Range, including its highest summit Denali, sits in Alaska

Snow melt in the Alaska RangeThe Alaska Range, including its highest summit Denali, sits in Alaska somewhat exposed to air currents and weather patterns blowing in from the ocean. These glacier-covered summits therefore might be particularly sensitive to changes in the average temperature driven by greenhouse gases. To investigate how mountain glaciers in the Alaska Range are responding to a warming world, in 2013 a team led by scientists at Dartmouth University collected ice cores on Mount Hunter, a 4,257 meter high summit about 15 kilometers south of Denali itself.The first image shows the team collecting the ice cores on this slope, the second image shows what they were looking for. When the snow at the top of the winter ice melts, it will re-freeze when the temperature drops and create one of those dark blue layers; the other layers are white because they still contain air bubbles. By counting the number of dark blue layers and measuring their thickness, the team could figure out how often melting events were happening and how big they were.Overall the team collected ice cores at this site that cover about 400 years of time. They found that, in the first 200 years of their core there are only a couple of melting events. By the time we reach the last few years, the number of melting events has increased by a factor of 57 and the amount of melting increased by a factor of 60. Many of those are found in years where the tropical Pacific Ocean is unusually warm, directly linking these new melting events to broader changes in the climate of the Pacific Ocean.The scientists used modern records of temperature and melting events to convert the increase in melting to an estimated increase in temperature, and found that since the melting events became more common in the mid 1800s, this site has warmed by at least between 1.2-2 °C – a rate comparable to or higher than that observed around the world.This is the first alpine record of melting events from this part of the world. It shows similar warming signals to those found elsewhere, showing that high altitude glaciers are affected by the same warming trends found elsewhere in the world.-JBBOriginal paper:https://bit.ly/2qlxJHxReference:https://bit.ly/2HpvbjD -- source link

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