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SCIENCE IN THE SEA: Ocean sampling day at Rothera

27 July, 2017 Rothera

Zoe Waring, the Rothera Marine Assistant provides us with an account of the recent Ocean Sampling Day at Rothera.

Since 2012, the Rothera Marine Assistant has been collecting samples for World Ocean Sampling Day (WOSD). These samples are taken on both the winter and summer solstice each year. WOSD is an international effort to better understand the global ocean’s microbiology and is run at British Antarctic Survey by Professor Melody Clark.

This year we sampled a week before the solstice as we were having a spree of good weather, this proved to be a wise choice as two weeks of stormy weather followed. It was a beautifully calm day allowing pancake ice to form in Ryder Bay, but Stella (our trusty water sampling vessel) handled it well and was able to force her way through the ice on our 3km journey to the deepest part of the bay.

The team travelling through pancake ice on their way to the sampling site.

Icy waters come hand in hand with the cold, surface waters were -1.7˚C and the air temperature was -7˚C. These cold conditions bring a unique set of challenges, seawater exposed to air this cold takes only moments to freeze. It also doesn’t take long for a layer of ice to form over most surfaces on the boat, including us!

To overcome this, an extra thermos flask of water is required (alongside the usual hot squash flask) as it is the only way of defrosting the attachments of niskin water samplers, which soon become frozen in place, making it impossible to take them on and off the winch line.

Deploying the niskin water sampler into Ryder Bay.

The other challenge during the sampling was keeping the CTD (standing for Conductivity, Temperature and Depth) batteries warm enough, so that it can record the water column properties during the entirety of its 1km round trip to the bottom of the bay and back (all hand winched of course).

Fortunately, we managed to overcome the challenges and the midwinter sampling for Ocean Sampling Day was a success.