Monday 27 August 2018

Sea Ice

A lonely figure drags his sledge across the ice.
One of the most interesting, enjoyable although, at times, frustrating aspects of my work as a field guide at Rothera is dealing with the sea ice.  Every winter the sea around Rothera freezes to some extent. If and when the ice is deemed to be strong and stable enough, we are allowed out on it for both science and recreation. I love being out on the ice. However, sea ice is hazardous and fickle material, and BAS are understandably cautious about what and where we are allowed on the ice.

Last winter was a very poor winter for the sea ice, and so I was really hoping for a decent sea ice season this year. Things did get off to a good start with a some cold and settled periods in June during which the sea froze. Over the next couple of weeks there where a few windy days, but the ice survived. The ice was deemed solid enough to venture onto in the more sheltered Hanger Cove for testing purposes on the 26th of June. The results were encouraging, and over the next few weeks other areas were tested and deemed suitable of science, and even a little recreation. The marine team got to go out and cut dive holes in the ice, and then go diving. They also managed some CTD sampling through the ice. The ice thickness was consistently between 30 and 40cm, and everything was looking good.
Marlon and Aurelia from the Marine team drilling to test the thickness of the ice. 
Kate cutting a dive hole in the ice in Hanger cove in late June.  
 Marlon and Aurelia about to go ice diving a couple of days later. 
By mid July, the sea ice situation was looking very promising, I remember thinking it would take a pretty substantial and prolonged storm to blow the ice out. Unfortunately, that is exactly what we got For the best part of a week winds of 30 to 60 knots howled down from the North. The ice survived the first few days, but then began to break up. By the flag up ceremony on the 21st of July, most of the ice to the South had blown out, and a couple of days later it had all gone. However, the ice to the North the ice hung on. Conditions suddenly changed again, the temperature plummeted again that the sea almost immediately refroze. Another cold and settled spell was followed by another mild and stormy period which blew out some, but not all, of the new ice. Since then there have been a few more colder days, and a few more blows. This has left a complex pattern of ice of different ages and thicknesses in different areas. Some area the ice is very solid,  in other areas we are now back to open water.

 It feels like quite a variable season ice wise, with good conditions rapidly giving way to poor conditions and vice versa. The forecast for the next few days is relatively calm, and am hoping for some more chances to get back out on the ice. However, one things I have learnt down here is that the Antarctic weather can be highly variable and unpredictable beast, so who knows what will happen.

A team on a short recreational trip onto the sea ice. 
Field guides testing the ice out in South Cove. The wharf and some of the marine science buildings can be seen in the background. 

A satalite image taken on the 22nd of July. The area of open water is clearly seen from it's much darker colour. Rothera is located on the peninsular on the top left of the area of open water. Due to a number of factors the sea ice around Rothera breaks up sooner than in other areas. 

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