| Helheim Glacier | |
|---|---|
| Helheim Gletscher | |
 View of the Helheim Glacier | |
  Location within Greenland | |
| Location | Sermersooq, Greenland |
| Coordinates | 66°21′N38°12′W / 66.350°N 38.200°W |
| Terminus | Helheim Fjord, Sermilik, North Atlantic Ocean |
Helheim Glacier is a glacier in the Sermersooq municipality, Eastern Greenland.
This glacier's name is derived from "Helheim", a modern term for aworld of the dead in Old Norse religion - Hel.
The Helheim Glacier is located on the eastern side of the Greenland ice sheet. It is one of Greenland's largest outlet glaciers. [1] [2] [3] It flows roughly in an ESE direction and feeds the waters of the Helheim Fjord, a branch at the northern end of the Sermilik (Egede og Rothes Fjord) system, where there are a number of other glaciers calving and discharging at rapid rates such as the Fenris and the Midgard Glacier. [4]
Helheim Glacier accelerated from 8 km (5.0 mi) per year in 2000 to 11 km (6.8 mi) per year in 2005. [5] Like many of Greenland's outlet glaciers, it is a common site where glacial earthquakes are monitored. [6]
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A glacier is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.
The Greenland ice sheet is a vast body of ice covering 1,710,000 square kilometres (660,000 sq mi), roughly near 80% of the surface of Greenland. It is sometimes referred to as an ice cap, or under the term inland ice, or its Danish equivalent, indlandsis. An acronym, GIS, is frequently used in the scientific literature.
An ice stream is a region of fast-moving ice within an ice sheet. It is a type of glacier, a body of ice that moves under its own weight. They can move upwards of 1,000 metres (3,300 ft) a year, and can be up to 50 kilometres (31 mi) in width, and hundreds of kilometers in length. They tend to be about 2 km (1.2 mi) deep at the thickest, and constitute the majority of the ice that leaves the sheet. In Antarctica, the ice streams account for approximately 90% of the sheet's mass loss per year, and approximately 50% of the mass loss in Greenland.
Jakobshavn Glacier, also known as Ilulissat Glacier, is a large outlet glacier in West Greenland. It is located near the Greenlandic town of Ilulissat and ends at the sea in the Ilulissat Icefjord.
The retreat of glaciers since 1850 affects the availability of fresh water for irrigation and domestic use, mountain recreation, animals and plants that depend on glacier-melt, and, in the longer term, the level of the oceans. Deglaciation occurs naturally at the end of ice ages, but glaciologists find the current glacier retreat is accelerated by the measured increase of atmospheric greenhouse gases and is an effect of climate change. Mid-latitude mountain ranges such as the Himalayas, Rockies, Alps, Cascades, Southern Alps, and the southern Andes, as well as isolated tropical summits such as Mount Kilimanjaro in Africa, are showing some of the largest proportionate glacial losses. Excluding peripheral glaciers of ice sheets, the total cumulated global glacial losses over the 26 year period from 1993–2018 were likely 5500 gigatons, or 210 gigatons per yr.
Glacier morphology, or the form a glacier takes, is influenced by temperature, precipitation, topography, and other factors. The goal of glacial morphology is to gain a better understanding of glaciated landscapes and the way they are shaped. Types of glaciers can range from massive ice sheets, such as the Greenland ice sheet, to small cirque glaciers found perched on mountain tops. Glaciers can be grouped into two main categories:
A cryoseism, ice quake or frost quake, is a seismic event caused by a sudden cracking action in frozen soil or rock saturated with water or ice, or by stresses generated at frozen lakes.
Ice sheet dynamics describe the motion within large bodies of ice, such those currently on Greenland and Antarctica. Ice motion is dominated by the movement of glaciers, whose gravity-driven activity is controlled by two main variable factors: the temperature and the strength of their bases. A number of processes alter these two factors, resulting in cyclic surges of activity interspersed with longer periods of inactivity, on both hourly and centennial time scales. Ice-sheet dynamics are of interest in modelling future sea level rise.
Petermann Glacier is a large glacier located in North-West Greenland to the east of Nares Strait. It connects the Greenland ice sheet to the Arctic Ocean at 81°10' north latitude, near Hans Island.
Kangerlussuaq Glacier is the largest glacier on the east coast of the Greenland ice sheet. It flows into the head of the Kangerlussuaq Fjord, the second largest fjord in East Greenland.
Glacial earthquakes are earthquakes as large as magnitude 5.1 that occur in glaciated areas where the glacier moves faster than one kilometer per year.
Zachariae Isstrom is a large glacier located in King Frederick VIII Land, northeast Greenland.
Nioghalvfjerdsbrae, sometimes referred to as "79 N Glacier", is a large glacier located in King Frederick VIII Land, northeastern Greenland. It drains an area of 103,314 km2 (39,890 sq mi) of the Greenland Ice Sheet with a flux of 14.3 km3 (3.4 cu mi) per year, as measured for 1996. The glacier has two calving fronts where the glacier meets the ocean, separated by Hovgaard Island. In July 2020, the northern offshoot, the Spalte Glacier broke away from Nioghalvfjerdsbrae and completely disintegrated.
Overdeepening is a characteristic of basins and valleys eroded by glaciers. An overdeepened valley profile is often eroded to depths which are hundreds of metres below the deepest continuous line along a valley or watercourse. This phenomenon is observed under modern day glaciers, in salt-water fjords and fresh-water lakes remaining after glaciers melt, as well as in tunnel valleys which are partially or totally filled with sediment. When the channel produced by a glacier is filled with debris, the subsurface geomorphic structure is found to be erosionally cut into bedrock and subsequently filled by sediments. These overdeepened cuts into bedrock structures can reach a depth of several hundred metres below the valley floor.
Subglacial streams are conduits of glacial meltwater that flow at the base of glaciers and ice caps. Meltwater from the glacial surface travels downward throughout the glacier, forming an englacial drainage system consisting of a network of passages that eventually reach the bedrock below, where they form subglacial streams. Subglacial streams form a system of tunnels and interlinked cavities and conduits, with water flowing under extreme pressures from the ice above; as a result, flow direction is determined by the pressure gradient from the ice and the topography of the bed rather than gravity. Subglacial streams form a dynamic system that is responsive to changing conditions, and the system can change significantly in response to seasonal variation in meltwater and temperature. Water from subglacial streams is routed towards the glacial terminus, where it exits the glacier. Discharge from subglacial streams can have a significant impact on local, and in some cases global, environmental and geological conditions. Sediments, nutrients, and organic matter contained in the meltwater can all influence downstream and marine conditions. Climate change may have a significant impact on subglacial stream systems, increasing the volume of meltwater entering subglacial drainage systems and influencing their hydrology.
Ice mélange refers to a mixture of sea ice types, icebergs, and snow without a clearly defined floe that forms from shearing and fracture at the ice front. Ice mélange is commonly the result of an ice calving event where ice breaks off the edge of a glacier. Ice mélange affects many of the Earth's processes including glacier calving, ocean wave generation and frequency, generation of seismic waves, atmosphere and ocean interactions, and tidewater glacier systems. Ice mélange is possibly the largest granular material on Earth, and is quasi-2-dimensional.
Midgard Glacier is a glacier in the Sermersooq municipality, Eastern Greenland.
Morris Jesup Glacier (Danish: Morris Jesup Gletscher, is a glacier in northwestern Greenland. Administratively it belongs to the Avannaata municipality.
Twila Moon is a scientist at the National Snow and Ice Data Center known for her work on the Greenland ice sheet.
{{cite web}}: CS1 maint: archived copy as title (link) Ekström, G., M. Nettles, and V. C. Tsai (2006)"Seasonality and Increasing Frequency of Greenland Glacial Earthquakes", Science, 311, 5768, 1756–1758, doi : 10.1126/science.1122112 
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