Cryosphere glossary
seasonal snow
(1) snow that accumulates during one season (2) snow that lasts for only one season.
seasonal thawing index
the cumulative number of degree-days above 0 degrees Celsius, calculated as the arithmetic sum of all the positive and negative mean daily air temperatures (degrees Celsius) for a specific station during the time period between the lowest point in the spring and the highest point the next fall on the cumulative degree-day time curve.
seasonally frozen ground
ground that freezes and thaws annually.
seasonally frozen layer (SFL)
the active layer in areas without permafrost.
seasonally thawed ground
ground that thaws and refreezes annually.
seasonally thawed layer (STL)
the active layer in permafrost areas.
seasonally-active permafrost
the uppermost layer of the permafrost which undergoes seasonal phase changes due to the lowered thawing temperature and freezing-point depression of its pore water.
second-year ice
sea ice which has not melted in the first summer of its existence; by the end of the second winter, it attains a thickness of 2 meters (6.6 feet) or more; it stands higher out of the water than first-year ice; summer melting has somewhat smoothed and rounded the hummocks, which accentuation of minor relief by differential melting may have caused others to develop; bare patches and puddles are usually greenish-blue.
sedimentary ogives
alternating bands of light and dark at the firn limit of a glacier; the light bands are usually young and lightest at the highest level up-glacier, becoming increasingly older and darker as they progress down-glacier.
segregated ice
ice in discrete layers or ice lenses, formed by ice segregation.
segregation potential
the ratio of the rate of moisture migration to the temperature gradient in a frozen soil near the 0 degrees Celsius isotherm.
semipermanent anticyclone
high pressure area largely predominate during a major portion of the year where an anticyclone appears on the mean monthly pressure charts.
semipermanent depression
slowly moving or motionless cyclone.
sensible heat
same as enthalpy; the heat absorbed or transmitted by a substance during a change of temperature which is not accompanied by a change of state; used in meteorology in contrast to latent heat.
sensible heat polynya
a polynya that forms from the upwelling of warm (above-freezing) ocean water from lower depths; these can form in mid-ocean areas, far from coasts or other barriers.
serac
an isolated block of ice that is formed where the glacier surface is fractured.
shear strength
in geology, describes the compressive strength (ability to withstand pushing forces) of soils; results from two internal mechanisms: cohesion between soil particles, and friction caused by contact between particles; variable among different soils.
shield
a screen to shield a rain-gauge from the influence of the wind, or to shield a thermometer against insolation.
shore lead
a stretch of navigable water between pack ice and the shore.
short-term strength
the failure strength of a material under a short-term loading (e.g. up to about 10 minutes in a uniaxial compression test).