Sea ice extent and concentration [in 'State of the Climate in 2006']

• Main Authors: Massom, R, Barreira, S, Scambos, T
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Meteorological Soc 2007
• Subjects: Earth Sciences; Physical Geography and Environmental Geoscience; Glaciology; Weddell Sea; Austral; Ross Sea; Amundsen Sea; Indian; Weddell; Greenwich; Sea ice
• Online Access: https://journals.ametsoc.org/toc/bams/88/6; http://ecite.utas.edu.au/129197

Sea ice extent anomalies varied widely during theyear, from record-low January and March extent(March was 18% relative to the 19792006 mean) torecord highs of +4% for September and October,based upon analysis of monthly mean SSM/I-derivedsea ice concentration data produced by the NSIDC Sea Ice Index project (Fig. 5.22; see Fetterer andKnowles 2004). However, by December 2006, sea iceextent was below average again. Strong regional variabilityis also apparent in ice extent and concentrationanomalies. For the austral sea ice minimum period(FebruaryMarch), the record low is primarily a resultof greater-than-average March retreat in theWeddell Sea. This is likely a result of the intensewarmth (up to 5C above average) in the easternWeddell in March, and a circulation pattern that favoredsouthward and eastward wind-driven drift ofthe pack. In the autumn growth season, positiveanomalies in the Amundsen Sea and western IndianOcean sectors are balanced by negative anomalies inthe South Atlantic (Weddell Sea) and Ross Sea/WPOsectors. The winter ice cover in August is characterizedby major negative anomalies (indicative of winddrivenice compaction) in the BellingshausenAmundsen Seas plus WPO sectors and a lessernegative anomaly skirting the Greenwich meridian.These are counterbalanced by equally large positiveanomalies in the Weddell Sea, Ross Sea, and IndianOcean sectors. This pattern persisted through SeptemberOctober. In fact, the Indian Ocean sectorexperienced large positive extent and concentrationanomalies from April through November. Locationsof extent anomalies, and the overall record extentduring the winter maximum, suggest an influencefrom the earlier positive SAM mode and strongpositive wavenumber-3 anomaly, and the presence oflower-than-average temperatures near the winter iceedge (see Massom et al. 2006; Raphael 2004).