Cryosphere glossary
macro-scale polygons
closed, multi-sided, roughly equidimensional, patterned ground features, typically 15 to 30 meters (16 to 33 yards) across; commonly resulting from thermal contraction cracking of the ground.
magnetic pole
either of the two points on the earth's surface at which magnetic meridians converge; the horizontal component of the magnetic field of the earth becomes zero at this point; also called the dip pole.
marginal crevasse
a crevasse near the side of a glacier formed as the glacier moves past stationary valley walls; usually oriented about 45 degrees up-glacier from the side wall.
marginal ice zone
a part of the seasonal ice zone that varies in width (100 to 200 kilometers, 62 to 124 miles) that extends from the ice edge into the ice pack, where waves and swells affect the ice; often characterized by highly variable ice conditions; in general, it is wider in the Antarctic than the Arctic.
Image
A scenic view within the marginal ice zone.
marine climate
a climate dominated by the ocean; because of the moderating effect of water, sites having this climate are considered relatively mild.
marine cryopeg
a layer or body of unfrozen ground, that is perennially cryotic (T < 0 degrees Celsius), forming part of the coastal or subsea permafrost.
maritime
of, relating to, or adjacent to the sea.
mass balance
the difference between accumulation and ablation on a glacier; usually calculated on an annual basis.
mass wasting
downslope movement of soil or rock on, or near, the earth's surface under the influence of gravity.
massive cryostructure
the cryostructure of frozen sand in which all mineral particles are bonded together with ice.
massive ice
a comprehensive term used to describe large masses of ground ice, including ice wedges, pingo ice, buried ice and large ice lenses.
massive-agglomerate cryostructure
the cryostructure of frozen silt or loam in which ice veins form an irregular three-dimensional network.
massive-porous cryostructure
the cryostructure of frozen sand and gravel in which all mineral particles are bonded together with ice, but larger pore spaces are not completely filled with ice.
maximum ice extent
the largest sea ice extent during a given year; maximum ice extent marks the end of the growth period for sea ice, and the start of the melt season
mean annual ground temperature (MAGT)
mean annual temperature of the ground at a particular depth.
mean annual ground-surface temperature (MAGST)
mean annual temperature of the surface of the ground.
mechanical properties of frozen ground
the properties of frozen ground governing its deformability and strength.
mechanical strength
the failure strength of a material under given loading conditions.
medial moraine
a ridge-shaped moraine in the middle of a glacier originating from a rock outcrop, nunatak, or the converging lateral moraines of two or more ice streams.
megadunes
unlike snow dunes that are piles of drifted snow, antarctic megadunes are long, undulating waves in the surface of the ice sheet that are 2 to 4 meters (6.5 to 13 feet) high and 2 to 5 kilometers (1 to 3 miles) apart; they are slightly rounded at their crests and are so subtle that a person on the ground cannot see the pattern.