Short-term Variation and Breakout Events

Landfast ice can experience some distinct short-term variations. Under this study, we are mostly interested in the type of fast ice change associated with abrupt breakout events caused by currents, winds and storm activities. 

The break-out events occur nearly every year along the Chukchi Sea coast near Barrow, Alaska.  Analysis of landfast sea ice dynamics based on analysis of marine radar data was continued to include the 2009-2010 ice season.  Break-outs of landfast ice which meets the criteria defined for this study (ice contiguous with the land and stationary for at least seven consecutive days) were

Made available by Miho Aoki, ARSC/UAF

Download or Expand Video

Requires QuickTime Player

Landfast ice can experience some distinct short-term variations. Under this study, we are mostly interested in the type of fast ice change associated with abrupt breakout events caused by currents, winds and storm activities. 

The break-out events occur nearly every year along the Chukchi Sea coast near Barrow, Alaska.  Analysis of landfast sea ice dynamics based on analysis of marine radar data was continued to include the 2009-2010 ice season.  Break-outs of landfast ice which meets the criteria defined for this study (ice contiguous with the land and stationary for at least seven consecutive days) were

identified, with two events of severity level 1 (break-out event removes less than half of the width of landfast ice present, gauged by distance of seaward landfast ice edge (SLIE) from shore, but brings SLIE at least about 0.5 km nearer to shore along stretch of coast impacted by break-out event) occurring on March 16 and May 29, and two break-outs of severity level 2 (break-out event removes at least half of the width of landfast ice present, but leaves  landfast ice of at least 1 km width intact) on March 24 and June 2. To gain insight into the processes driving break-outs and linking these to the large-scale atmospheric, ice and ocean circulation patterns examined by the other groups in this collaborative study, we report results from these case studies below.

A break-out event of severity level 2 occurred on February 27, 2009 in which the resultant seaward landfast ice edge (SLIE) appears to have been formed in the weeks leading up to the break-out event by deformation caused by convergence of pack ice on the pre-break-out SLIE.  The ice added to the landfast ice cover during this sequence of events remained stationary throughout the ice season, not being lost until breakup in late June/early July.  The processes observed by the radar system in February 2009 provide insight into the process of in-situ deformation that may possibly have resulted in the grounding of landfast ice ridges, stabilizing the landfast ice cover.  The high temporal resolution of the radar system also allows comparison of the timing of the ice events with atmospheric and oceanic conditions which contribute to those events’ occurrence.  All radar animation sequences can be viewed at http://seaice.alaska.edu/gi/data/barrow_radar.
The break-out event occurred at a time directly after a changes in atmospheric conditions (Figure a).  The temperature began to rise shortly before the break-out occurred, which coincided with a rise in sea level pressure from a from a week-long low.  The wind also shifts nearly 180°, from south-southwest to nearly due north, in a matter of hours leading up to the break-out event.  Further analysis is to be carried out on data provided by the collaborators in this project to examine how atmospheric conditions may have contributed to or triggered the break-out events, including oceanic conditions from available data.

graphs

Break-out events occur nearly every year along the Chukchi Sea coast near Barrow, Alaska.  For animations of sea ice movement observed by UAF’s coastal marine radar, visit: http://seaice.alaska.edu/gi/data/barrow_radar
Good examples of break-outs are on the following dates:
March 31, 2007
May 28, 2007
March 29, 2008
February 5, 2009
February 27, 2009
March 24, 2010

Site developed and maintained by Polar Science Center. Copyright © 2010, Seattle, Washington, USA
This project is supported by the Nation Science Foundation, Arctic Natural Science Program.