Antarctic report – measuring the melt

By Guest Author 16/01/2012

by Dr Craig Stevens, Physical Oceanographer at the National Institute of Water and Atmospheric Research (NIWA)

This is a new blog series describing the day-to-day work for an experiment looking at a coastal ocean flow in Antarctica. Unlike most oceanography the work is conducted from camps on sea ice.

This is the frozen skin of the ocean perhaps a few metres thick, sufficient for us to set up tents, drill through the ice, and then sample. This water is quite special in that it is extremely cold but relatively fresh. Indications are that it plays a big role in how sea ice forms in the wider southern ocean. The growth and decay of sea ice is one of the key elements in global climate science.

Meltpond showing wind turbines in the background - Craig Stevens
Meltpond showing wind turbines in the background - Craig Stevens

Over the past decade our group (NIWA, IRL, U. Otago) has done quite a bit of work in Southern McMurdo Sound looking at how the ocean beneath the Ross Ice Shelf finds its way into the local ocean. My specialty being the rate at which it mixes with the surrounding waters.

Part of this work has been looking at the evolution of the outflow as it (presumably) hugs the coast moving north. A logical extension of this is to repeat our southern sampling in the far north of the region. To this end, in the present field season we’re planning work with Italian colleagues out of their base in the Terra Nova Bay area some 200 km to the north of Scott Base.

After a brief delay we got away from Christchurch at around 11 pm on January the 8th. The US C-17 transport was quite full as a flight had been cancelled a few days previous so there wasn’t a spare seat on our flight. The views as we crossed the Victoria Land coast well to the north of McMurdo Sound were fantastic but they quickly gave way to cloud cover. This had me a little nervous as it’s not unheard of for the flight to turn back even once it has arrived in the McMurdo area due to poor weather and visibility. Ten hours flying to be where you started doesn’t make for a great feeling of achievement. Of course compared to 2 weeks battling the southern ocean in a ship this seems a little soft.

The late departure meant we didn’t arrive until 4:30 a.m. — the landing was followed by an hour long crawl into Scott Base on a big transporter bus. It was actually snowing quite heavily by the time we made it in to base. This is unusual in itself — most of the time snow in Antarctica is actually just wind-blown material. While we are trying to deploy more gear that automatically samples year-round, we typically work in the field in the October-December period as this is when sea ice operations are more feasible.

So it is strange for me to be here so late in the field season with lots of exposed rock and dirt around Scott Base and lots of melt ponds on the sea ice out the front of Scott Base. This melting will continue to weaken the sea ice making it more susceptible to breaking up. In fact last year was the biggest break up in the last 12 or so years.

(*K132? It’s our experiment reference number and forms the basis of any communications and decisions here. It’s specifically associated with a grant from the prestigious Marsden Fund at the Royal Society of New Zealand to look at how melting ice influences ocean circulation.).

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