Sea Ice Report
Field Safety Training Program
9 December, 2004  [NOTICE: The following report is presented on this web site as an informational reference only. Persons in the vicinity of Ross Island must consult their appropriate safety representives for current information prior to contemplating any travel off established marked routes. Remember: this could happen to you! --Bill] Hello to everyone, with an updated sea ice report. This report in whole is made possible by the sharing of valuable information from many different science groups and work centers, notably Jeff Scanniello, McMurdo area surveyor, Fleet Operations and Jess Walker, our GIS mapping specialist. Although sea ice operations are quickly coming to a halt, we will continue to monitor the local sea ice conditions for both ongoing science projects and for the expected arrival of the US Coast Guard cutter. Field Safety Training Program Having been out of town and away from the sea ice for more than two weeks, I was quite surprised at the sudden change in conditions we are seeing near town. With the seemingly warm air temperatures being experienced these days, the sea ice surface is quickly turning to slush and deep melt pools are forming. Most of this deterioration can be attributed to the surface debris blown onto the ice from past windstorms. This is the main cause of the accelerated movement of airplane operations from the Ice Runway out to Williams Field on the McMurdo Ice shelf. Contrary to what many of us believe to be an unusually warm season, the factual data from the weather department points out that the temperatures we are experiencing lately are more normal than the cooler weather patterns of the past two years. The sea ice is now officially closed for all recreational activities. After the last of the sea ice field camps are pulled early next week, all sea ice travel will likely be suspended, pending consultation with Dave Bresnahan, the NSF representative. Any subsequent travel onto the sea ice must first be discussed with FSTP and only then may travel be approved on an as-need basis. Over the last three weeks the internal sea ice temperature has risen from comfortable period two conditions (14-23(F/-10 to -5(C) to the upper levels of period three conditions (23-27(F/-5 to -3(C). Specifically, the areas around the Ice Runway registered an average of 23(F (-5(C) and last season's shipping channel averaged 24.5(F (-4(C). By comparing these figures to last season's internal sea ice temperatures of 20(F (-7(C) around the Ice Runway and 20.7(F (~ -7(C) in the shipping channel, we can see why the runway move is two weeks ahead of the move last December. Once the internal ice temperatures begin to elevate into the low 20's (-7 to -5(C), the warming processes speed up and the trend does not slow down until the return of the sunsets in March. At the four temperature gauges placed 20, 40, 60, and 80 miles away from McMurdo Station, temperature readings as of last night were 25.5(F and 27(F at 20 and 40 miles respectively, while the 60 and 80-mile readings were a bit warmer at 28.5(F and 29(F respectively. Interestingly, the conditions north of Ross Island seem to be holding fairly stable showing only slight increases in temperature and minimal loss of thickness. We will continue checking these stations in our sustained assessment of the overall sea ice conditions. The surface conditions near town are quite visibly poor and at the forefront of our minds right now. Similarly, the conditions of the sea ice further north from McMurdo are showing increased melt pool formation and incredibly rapid snowmelt. In some areas where the snow cover was >48" (122cm) thick just three weeks, we are seeing exposed blue sea ice. Much of the snowmelt can be attributed to the wind deposited debris being heated by the intense solar radiation. The first year ice north of Cape Evans is where the majority of the melt pool formation is happening. Starting near the Barne Glacier area and moving north, the whole sea ice surface is beginning to melt into slush, creating sizable "lakes".
Along with the surface melting, the increased formation of open water leads continues. The newly formed crack at the Barne Glacier that was mentioned in the previous sea ice report has shown signs of growth. This open crack measured 15" (38cm) wide three weeks ago and is now more than 30" (76cm) wide. Another crack in the same vicinity has recently opened with an average width of 36" (92cm) and much seal activity. Still more open water cracks have been observed off of Cape Barne ranging in width from 6" (15cm) to more the 12" (30.5cm). Numerous large cracks between Cape Royds and Cape Bird continue to widen, with the largest two being >25' Along this line of thought and of particular interest these days are the locations of both the sea ice edge and the large icebergs north of Ross Island. I have included a recent satellite image of the McMurdo Sound area that clearly shows the relationship of the local icebergs and the extent to which the fast-ice is still intact. As of today, the ice edge is approximately 80 miles (~130km) away near the tip of B-15K, the thin sliver iceberg just north of Beaufort Island. The movement of B-15A is being closely monitored as it inches toward the Drygalski Ice Tongue. It's outcome waits to be seen. Equipment Operations/Established Roads Now that the Ice Runway operations have ceased, the Scott Base transition will begin to see the brunt of vehicle traffic. If you are planning to drive out to William's Field, please stay informed as to what vehicles and/or equipment are allowed to travel on the snow road, as it requires an incredible amount of maintenance. The actual transition from Ross Island onto the sea ice/ice shelf is also a very temperamental area subject to a lot of preservation work, so be aware of any equipment working in the area. As always, if there are any notable observations made during travel on the sea ice, please email me at brian.Johnson@usap.gov or call the FSTP office at x2345 to report your findings. Here's wishing you an enjoyable holiday season and safe travels in the weeks to come.
Brian Johnson |
