A shrinking giant
The Northern Patagonian Ice Field is a 4,200 square kilometer remnant of the vast Patagonian Ice Sheet, which covered the region during the last ice age. It is the second-largest continuous mass of ice outside the polar regions. This immense body of ice is located entirely within Chile's Laguna San Rafael National Park. Its survival in a temperate latitude depends on its high elevation, typically between 1,100 and 1,500 meters, and a cool, moist oceanic climate.
The ice field feeds 28 outlet glaciers. The two largest, San Quintín and San Rafael, flow west towards the Pacific Ocean. San Rafael is being the tidewater glacier closest to the equator and for its rapid movement, flowing at about 7.6 kilometers per year. This makes it one of the fastest-moving glaciers in the world. The ice field also contains the highest peak in Patagonia, Monte San Valentín, which has a commonly cited elevation of 4,058 meters.
A record of climate change
The glaciers of Patagonia are thinning at some of the highest rates on the planet, with ice loss per unit area exceeding that of Alaska or Greenland. Between 1995 and 2000, the average rate of ice thinning in Patagonia more than doubled compared to the period from 1975 to 2000. The rate of sea-level rise contribution from Patagonian glaciers also doubled in the early 21st century.
This accelerated melting is driven by atmospheric warming. Studies have documented significant retreats of major glaciers. For example, between 2001 and 2011, the Steffen Glacier's rate of retreat more than doubled compared to the previous two decades, and it lost a lateral tongue that retreated 3.1 kilometers. During the same period, the Gualas Glacier retreated 1.9 kilometers. The rapid loss of ice has geological consequences; as the ice disappears, the unburdened land beneath is rising in a process called glacial isostatic adjustment. This uplift is happening unusually fast in Patagonia due to hotter, less viscous mantle material flowing into a gap between tectonic plates beneath the region.