Greenland, the world’s largest island, is largely covered by a massive ice sheet. This vast ice mass, often referred to as the Greenland Ice Sheet, spans approximately 1.7 million square kilometers, covering about 80% of the island’s surface. It is second only to Antarctica’s ice sheet in size. Understanding the persistent presence of this ice requires examining a combination of geographic, atmospheric, and historical factors.
Greenland’s Geographic and Topographic Features
Greenland’s location at high northern latitudes, between 59° and 83°N, directly contributes to its cold climate, positioning much of the island within the Arctic Circle. This proximity to the North Pole naturally results in lower average temperatures. The terrain also plays a significant role in accumulating and maintaining ice. The interior features a saucer-like basin with a high, dome-shaped central plateau.
This central ice dome reaches over 3,000 meters above sea level, contributing to colder conditions at higher altitudes. This elevated topography forces moist air to rise, cool, and release its moisture as snow, which then contributes to the growth of the ice sheet. The surrounding coastal mountains help to contain this ice mass, preventing it from easily flowing into the sea.
Climatic Factors Sustaining the Ice
Greenland experiences an Arctic climate characterized by consistently low temperatures throughout the year, especially over the interior ice sheet. Average annual temperatures on the inland ice can plummet to -9°C (15.8°F), with winter averages reaching -20°C (-4°F) and extreme lows around -50°C (-58°F) near the summit. The lowest temperature ever recorded in the Northern Hemisphere, -69.6°C (-93.3°F), occurred near the summit of the Greenland Ice Sheet in 1991.
These frigid conditions are largely maintained by cold air masses originating from the Arctic, which frequently sweep across the island. While coastal areas can experience slightly milder conditions due to oceanic influences, the vast interior remains locked in a perpetual freeze. Significant snowfall contributes to the continuous accumulation of ice. This consistent precipitation ensures a steady supply of new snow, which compacts over time to replenish the ice sheet.
The Ice Sheet’s Role in Its Own Preservation
The Greenland Ice Sheet actively contributes to its continued presence through a phenomenon known as the albedo effect. Ice and fresh snow are highly reflective, reflecting a significant portion of incoming solar radiation back into space. This high reflectivity helps to keep the ice sheet’s surface cool by preventing it from absorbing much of the sun’s energy.
This reflective property creates a positive feedback loop: the ice keeps the area cold, which allows more snow and ice to accumulate, further enhancing its reflectivity and perpetuating the cold. The sheer thickness of the ice sheet, averaging 1.67 kilometers and reaching over 3 kilometers at its maximum, also acts as an insulating layer. This immense depth prevents the ground beneath from warming, maintaining the frozen conditions necessary for the ice sheet’s stability.
The Long History of Ice Formation
The Greenland Ice Sheet has a deep history, accumulating over vast geological timescales. A single, coherent ice sheet covering most of the island formed approximately 2.6 to 3 million years ago. This formation period spans multiple glacial and interglacial periods, with the ice sheet expanding and contracting in response to past climate shifts.
The process involves successive layers of snow falling and compacting over millennia. As new snow accumulates, its weight presses down on older layers, gradually transforming snow into denser firn, and eventually into solid glacial ice. The oldest known ice within the Greenland Ice Sheet is approximately 1 million years old. During the Last Glacial Maximum, the ice sheet was even more expansive than its current size, covering an area 40% larger.