West Antarctic Peninsula sea ice in 2005: Extreme ice compaction and ice edge retreat due to strong anomaly with respect to climate

• Published in: Journal of Geophysical Research
• Main Authors: Massom, Robert A., Stammerjohn, Sharon E., Lefebvre, Wouter, Harangozo, Stephen A., Adams, Neil, Scambos, Theodore A., Pook, Michael J., Fowler, Charles
• Other Authors: UCL
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 2008
• Subjects: Antarc*; Antarctic; Antarctic Peninsula; Sea ice
• Online Access: http://hdl.handle.net/2078.1/36795; https://doi.org/10.1029/2007JC004239

In September-October 2005, the juxtaposition of low-and high-pressure anomalies at 130 degrees W and 60 degrees W, respectively, created strong and persistent northerly airflow across the West Antarctic Peninsula (WAP). This had a major impact on regional sea ice conditions, with extreme ice compaction in the Bellingshausen and East Amundsen seas (60 degrees W-130 degrees W) but divergence in the West Amundsen and East Ross seas. This resulted in the former in a highly compact marginal ice zone and ice cover, mean modeled ice thicknesses of >5 m, and an earlier-than-average maximum extent (mid-August). While rapid ice retreat in late winter-spring created a major negative ice extent anomaly, compact ice persisted in the subsequent summer. Other effects were anomalies in air temperature (of +1 degrees C to +5 degrees C) and precipitation rates (to >2.5 mm/d). The patterns in late 2005 are consistent with the occurrence of a weak La Nina and a near-neutral Southern Annular Mode, with a quasi-stationary zonal wave three pattern dominating hemispheric atmospheric circulation. Once a compact ice edge was created, it took only one additional week of strong winds to "solidify'' the pack in place. Conditions in 2005 are analyzed in the context of 1979-2005 and compared with the springs of 1993, 1997, 1999, 2001, and 2004. A statistically significant increase of the northerly 10-m wind component between 110 degrees W and 125 degrees W occurred in the Septembers of 1979-2005. No clear trends occur in other spring months. This work underlines the key importance of ice dynamics in recent changes in the WAP sea ice regime.