Thawing Permafrost
Permafrost has warmed by up to 2°C in
recent decades and the depth of the layer
that thaws each year is increasing in many areas. Permafrost's southern limit is projected to shift north-ward by several hundred kilometers during this century.
Arctic Climate Trends
Rising Temperatures
Temperatures have increased sharply in recent decades over most of the region, especially in winter. Winter increases in Alaska and
western Canada have been around 3-4°C over the past half
century. Larger increases are projected this century.
Rising River Flows
River discharge to the ocean has increased over much of the arictic during the past few decades and spring peak river flows are occurring earlier. These changes are projected to accelerate.
Declining Snow Cover
Snow cover extent has declined about 10% over the past 30 years. Additional decreases of 10-20% by the 2070s are projected, with the greatest declines in spring.
Increasing Precipitation
Arctic precipitation has increased by about 8% on average over the past century. Much of the increase has come as rain with the largest increases in autumn and winter. Greater increases are projected for the next 100 years.
Diminishing Lake and River Ice
Later freeze-up and earlier break-up of river and lake ice have
combined to reduce the ice season by one to three weeks in some areas. The strongest trends are over North America and western Eurasia.
Melting Glaciers
Glaciers throughout the Arctic are melting. The especially rapid retreat of Alaskan glaciers represents about half of the estimated loss of mass by glaciers worldwide, and the largest contribution by glacial melt to rising sea level yet measured.
Melting Greenland Ice Sheet
The area of the Greenland Ice Sheet that experiencs some melting has increased about 16% from 1979 to 2002. the area of melting in 2002 broke all previous records.
Retreating Summer Sea Ice
The average extent of sea-ice cover in summer has declined by 15-20% over the past 30 years. this decline is expected to accelerate, with the near total loss of sea ice in summer projected for late this century.
Rising Sea Level
Global and arctic sea level has risen 10-20 centimeters in the past 100 years. About an additional half meter of sea-level rise (with a range of 10 to 90 cm) is projected to occcur during this century. The increase in the Arctic is projected to be greater than the global average. The slope of the land and whether the coastline is rising or falling also affects the relative sea-level rise in each location.
Ocean Salinity Change
Reduced salinity and density have been observed in the North Atlantic Ocean as melting ice and increasing river runoff have added more freshwater to the ocean. If this trend persists, it could cause changes in ocean circulation patterns that strongly affect regional climate.
Center for Environmental Education and Information
