In the case of Antarctica's Amery Ice Shelf, the calving area resembles a loose tooth. The slow formation of a large rift in an ice shelf is a process that can take a decade or longer. Therefore, they sometimes occur in northern Greenland, but are most common in Antarctica. Calving of these types of icebergs usually results from rifts that reach across the shelf. Huge, tabular icebergs are unique to large floating ice shelves and ice tongues. There are different types of calving, and they are more or less common depending on the environment. Credit: European Space AgencyĬalving is a process by which chunks of ice break off from ice shelves (the extensions of land ice that float on an ocean) and glaciers. The tabular shapes are common in Antarctica where large rifts cross floating ice shelves and ice tongues resulting in more geometric shapes. This almost cloud-free image was captured on February 11, 2020, by the Copernicus Sentinel-2 mission it shows the freshly broken icebergs in detail. The Pine Island Glacier in Antarctic spawned an iceberg over 300 square kilometers (116 miles) in February 2020, quickly shattering into pieces. Stresses from ice flowing over bedrock or around islands can also cause fracturing, and at the front edge of the ice, fracturing can lead to iceberg calving. With the ice in contact with the ocean, ocean heat may melt the floating ice from the underside, thinning the ice sheet and weakening it. In these areas, the location of the edge of the ice sheet is sensitive to both ocean conditions and the amount of ice fracturing (crevasses or rifts). If, however, the ice sheet outlet is land terminating (ending before the ocean), then water will flow into a river.įor much of the fast-flowing ice in Greenland and Antarctica, ice flow terminates at the ocean, as a tidewater glacier (not fully afloat) or an ice tongue or ice shelf (fully floating thick sheets of ice on the ocean). If the ice sheet outlet glacier is marine terminating (ending at the ocean), then water will flow directly into the ocean. When meltwater travels through the ice sheet, it can travel through moulins (vertical channels), crevasses (deep open cracks), and changing tunnels. In other cases, the meltwater can travel through various channels to run out from underneath the ice sheet or pour off its surface. Ice sheet surface meltwater may refreeze before it leaves the ice sheet. In areas where summer surface melt exceeds winter snowfall, old interior layers in the ice sheet are exposed. Ice sheets flow outward from their dome-like centers, where they are generally thickest, and push ice outward towards the ocean. Subglacial surfaces can be quite variable, from mud-like till to bedrock to mixed environments. What is underneath a glacier also influences its speed. Instead, the glacier ice can lose contact with the ground and become a floating ice shelf. Near the coast, ice speeds can reach hundreds of meters or even many kilometers per year, as the ice flows into “outlet glaciers.” In some instances, fast ice motion can begin farther towards the ice sheet interior, creating “ice streams.” As outlet glaciers move ice out to the ocean, that ice may not break off. Near the summit of an ice sheet, where the slope is the lowest, flow speeds are generally a few centimeters to a few meters per year. Ice sheet flow is a function of surface slope, ice thickness, and whether the ice can slide on the bed. The highest areas on the West Antarctic and the Antarctic Peninsula Ice Sheets are about 2,500 meters (8,200 feet). The Greenland and East Antarctic Ice Sheets are roughly 3,000 to 4,000 meters (10,000 to 13,000 feet) high at their summits. Unlike a glacier, which generally flows in one direction, an ice sheet flows outward in all directions from the center. The canyon was formed by an outflow stream from the lake that flowed to a large moulin at the end of the canyon. In this water-filled canyon on the Greenland Ice Sheet, snow has dammed outflow from a nearby supraglacial lake, but nearby melt streams continue to fill sections of the canyon where snow has not accumulated.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |