| Summary: | Progress Code: completed Statement: This indicator is now OBSOLETE. These data are no longer archived in this location, and are therefore not up-to-date. At Davis, where the water depth near the station is relatively shallow, there is little heat transfer from the ocean to the ice, and the thickness is largely determined by atmospheric conditions, predominantly temperature and snow cover. At Mawson, where ocean depths are over 200 m, interannual variability of ice thickness is also influenced by changes in oceanic heat flux. Long-term statistics are maintained for each site of the date of ice formation, maximum thickness, date of maximum thickness, date of any mid-season breakouts, and date of final breakout of the fast ice. Incomplete historical records exist for Mawson back to 1954 and for Davis back to 1958. Simple (e.g. Allison, 1981) or more complex (Heil et al., 1996) thermodynamic modelling of the growth of the ice cover can be used to estimate seasonal and interannual variations in the oceanic heat flux. This indicator is no longer maintained, and is considered OBSOLETE. INDICATOR DEFINITION Regular measurements of the thickness of the fast ice, and of the snow cover that forms on it, are made through drilled holes at several sites near both Mawson and Davis. TYPE OF INDICATOR There are three types of indicators used in this report: 1.Describes the CONDITION of important elements of a system; 2.Show the extent of the major PRESSURES exerted on a system; 3.Determine RESPONSES to either condition or changes in the condition of a system. This indicator is one of: CONDITION RATIONALE FOR INDICATOR SELECTION Each season around the end of March, the ocean surface around Antarctica freezes to form sea ice. Close to the coast in some regions (e.g. near Mawson and Davis stations) this ice remains fastened to the land throughout the winter and is called fast ice. The thickness and growth rate of fast ice are determined purely by energy exchanges at the air-ice and ice-water interfaces. This contrasts with ...
|
|---|