Arctic Ice Thickness
The Polar Ice Prediction System (PIPS 2.0) is the operational model run by the Naval Oceanographic Office (NAVO) for sea ice forecasting. The PIPS 2.0 coupled ice-ocean model forecasts ice conditions from the North Pole south to 30°N latitude, where daily values of ice thickness have been provided since October 1998. The forecasts are initialised using buoys and ice concentration data from a Special Sensor Microwave Image (SSM/I). The forecast values of ice thickness use weather forecasts, with the results available as GIF images. A typical one is provided in Figure 1. The thickness of the ice is given by a colour scale which goes from 0.5 to 5.0 m in steps on 0.25 m, though in fact there appear to be no pixels in the 0.5 to 0.75 m range.
To derive areas and volumes of ice, the graphic images were downloaded and analysed by counting the numbers of pixels of each colour provided. The projection used is not an equal area projection and as such, the areas derived are approximate (hence the use of the ‘nominal’ on the following charts). They were based pro-rata on a scanned image of Greenland. However, it should also be noted that occasionally there were anomalous values, for example for a few days the Caspian and Aral seas were included as ice cover.
Figure 2 shows the area and volume of sea ice from October 1998 to December 2010. These figures only apply for ice greater than 0.75 m thick and consequently the areas are less than those shown elsewhere on this site. None-the-less they demonstrate a similar pattern. In general the volume and area show maxima and minima at similar times but after the low summer minimum of 2007 the ice area recovered well in 2008 but the volume did not. This can be seen more clearly on the chart on ice thickness in Figure 3, which shows that minimum ice thickness was less in 2008 than in 2007, giving some support to those who said the ice that year was “rotten”.
It is interesting to note that the ice thickness is bi-modal; one maximum occurs in May, when the ice area has just passed its maximum, and the second in September near to the point when it is at its minimum. This can be seen more clearly in Figure 4, which compares average thickness with current ice thickness. Figure 4 confirms that at the start of 2010 the ice thickness was less than the average for the preceding 10 years but as of December 2010 it had recovered to its average value.
Note: Dec 2011. The PIPS system used to produce the ice thickness estimates developed an anomaly during 2011. A revised system is being developed but until that is done we will not be updating our web site.
Data sources:Hibler, W.D. III and K. Bryan. 1987. A diagnostic ice ocean model. 1. Phys. Oceanogr., 1 7(7), 987-1015.
Hogan T.F. and Rosmond T.E. The description of the Navy Operational Global Atmospheric Prediction System’s spectral forecast model. Mon. Weather. Rev. 119 , 1786 to 1815, 1991
For more information see: http://www7320.nrlssc.navy.mil/pips2/info.html