Omnifocus 41/22/2024 ![]() ![]() ![]() Lakes in the northern United States are freezing later and thawing earlier compared with the 1800s and early 1900s. Every glacier was smaller in 2015 than in 1966. The total surface area of the 37 named glaciers in Glacier National Park decreased by about 34 percent between 19. Visitors from far and wide are drawn to Glacier National Park in Montana for its dramatic beauty and its glaciers. A Closer Look: The Glaciers of Glacier National Park.The Arctic has been the dominant source of global sea-level rise since at least 1972. Of the eight Arctic glaciers with long-term measurements, seven have steadily lost ice since the mid-20 th century. Arctic Glaciers. Rapid changes are occurring across the Arctic, where air temperatures are warming twice as fast as the global average temperature.The loss of ice from glaciers has contributed to the observed rise in sea level. Glaciers in the United States and around the world have generally shrunk since the 1960s, and the rate at which glaciers are melting has accelerated over the last decade. This accounts for about one-quarter of the total observed sea level rise during that time period. The total amount of ice lost from 1992 to 2018 was enough to raise sea level worldwide by an average of roughly seven-tenths of an inch. Since 1992, the giant ice sheets that cover Greenland and Antarctica have each lost more than 100 billion metric tons of ice per year on average. Slight increases in Antarctic sea ice are outweighed by the loss of sea ice in the Arctic during the same time period. Antarctic sea ice extent in September (annual maximum) and February (annual minimum) has increased slightly overall since 1979, though it has decreased in the last few years. The length of the melt season for Arctic ice has grown, and the ice has also become thinner, which makes it more vulnerable to further melting. The annual minimum extent of Arctic sea ice has decreased over time, and in September 2022 it was the 11 th smallest ever recorded. The area covered by ice is typically smallest in September, after the summer melting season. Part of the Arctic Ocean is covered by ice year-round. Because of their light color, snow and ice also reflect more sunlight than open water or bare ground, so a reduction in snow cover and ice causes the Earth’s surface to absorb more energy from the sun and become warmer. For example, melting ice sheets on Greenland and Antarctica add fresh water to the ocean, increasing sea level and possibly changing ocean circulation that is driven by differences in temperature and salinity. Such changing climate conditions can have worldwide implications because snow and ice influence air temperatures, sea level, ocean currents, and storm patterns. Conversely, reduced snow and ice could present commercial opportunities for others, including ice-free shipping lanes and increased access to natural resources. ![]() For communities in Arctic regions, reduced sea ice could increase coastal erosion and exposure to storms, threatening homes and property, while thawing ground could damage roads and buildings and accelerate erosion. Reduced snowfall and less snow cover on the ground could diminish the beneficial insulating effects of snow for vegetation and wildlife, while also affecting water supplies, transportation, cultural practices, travel, and recreation for millions of people. This chapter focuses on trends in snow, glaciers, and the freezing and thawing of oceans and lakes. Climate change can dramatically alter the Earth’s snow- and ice-covered areas because snow and ice can easily change between solid and liquid states in response to relatively minor changes in temperature. The Earth’s surface contains many forms of snow and ice, including sea, lake, and river ice snow cover glaciers, ice caps, and ice sheets and frozen ground. ![]()
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