200
180
160
140
120
1995
1998
100
Linear (1995)
Linear (1998)
80
60
40
20
0
0
20
40
60
80
100
120
140
160
180
200
Ship Total (Level+Snow+Ridge)Thickness (cm)
Figure 7. Scatterplot comparing the thickness from the NIC ice charts and ship-based
observations as in Figure 7 without the error bars with the linear regression line for 1995 and
1998 superimposed on the points.
Analysis of Sea-Ice Thickness
Using the NIC charts, the sea-ice extent, seasonal and interannual thickness distribution
and the mass balance are derived for the Ross Sea. This will be used to establish a framework
for creating a Southern Hemisphere sea-ice thickness climatology and enable the detection of
any trends in the distribution of Antarctic sea-ice thickness. The analysis performed in ArcGIS
provides visual and quantitative tools for examining sea-ice extent and spatial and interannual
variability between the growth and melt seasons.
The visual analysis afforded in ArcMap enables the extent of sea-ice (Figure 8) to be
tracked and the spatial variability in the pack to be investigated. The sea-ice extends to 61S
latitude in June 1995 and to 60S latitude in June 1998, and continues to increase northward
towards the maximum in September (not shown). During the melt season in January 1999 and
2000, the sea ice extends to only 63S latitude in the western portion of the Ross Sea sector with
a minimum in February. Using the GIS, researchers are able to depict the advancement and
retreat of sea ice through the annual cycle, as well as determine the area of sea-ice cover.
Additionally, the visual comparison of the spatial fields in the GIS enable the interannual
variability in sea-ice conditions to be monitored between years. As shown in Figure 5 (upper
panel), sea ice is not as thick during June 1998 as in June 1995 with the larger areal extent of
first-year thick (light pink) and multi-year sea ice (darker pink) even though the sea-ice extent is
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