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Tuesday, 12 May 2015

Floes, leads and CTD’s: The state of the ice at 83°

The air at 82° 23’ North is crisp and still, and the afternoon sun blazes down on the ice floe we hope to call home for the next three months. The gentle hum of the Research Vessel (R/V) Lance’s engine some 300 metres away, and the regular click of the winch deploying our oceanographic profilers below the ice sheet, breaks the all-consuming silence in this seemingly barren wilderness. A walkie-talkie crackles into life from my pocket; a message from the ship! Norwegian isn’t my strong point, but one word in particular causes my ears to prick up in concern: ‘Isbjørn’, or, ‘Polar Bear’. For those aboard the Lance, this is a prime opportunity to grab a camera and be the envy of all their friends back home. For those of us ambling about on the ice, away from the cosy confines of our floating laboratory, pulses quicken as we try to withdraw our equipment without compromising the all-important data…

Constructing hole for on-ice CTD (Image credit: Torbjørn Taskjelle, UiB)
The Norwegian Young Sea Ice Cruise (N-ICE2015) is a truly international effort, with researchers from over a dozen institutions coming together to gather data from the Arctic ice cap, as well as the surrounding atmospheric and oceanic currents. Initiated by the Norwegian Polar Institute, the R/V Lance plans to drift with the sea ice for six months, from January to June 2015. After a brief hiatus in Svalbard to change crew in March, I was able to join the ship as it steamed back into the ice, where it would get ‘refrozen’ for the remainder of the expedition.

It was never going to be plain sailing from Longyearbyen to our target latitude of 83° North. Battling against the wind, snow and pack ice in increasingly treacherous conditions had left those seeking warmer climes to put the ship’s impressive DVD collection to good use! That being said, efforts to measure this dynamic polar wilderness were already being undertaken from the offset.

Atmospheric scientists have been releasing weather balloons twice per day to profile the troposphere and stratosphere. Biologists collected water samples as we skimmed over the continental shelf off Svalbard, in order to divulge information on the bloom of primary producers found in shallower waters at this time of year. I managed to get better acquainted with my new friend for the month: the Conductivity-Temperature-Depth instrument, or CTD, which is deployed through the water to measure parameters such as salinity and temperature. With this information we can look at the width and depth of contrasting water masses, allowing us to track their progress at specific points.

As a member of the physical oceanography work package, I’m interested in how warm, salty Atlantic water, formed in the tropics off the eastern United States, travels north into the Arctic basin, and how its heat is distributed in the colder Arctic waters. By measuring the turbulence and temperature flux of this relatively shallow ‘tongue’ of Atlantic water (approximately 200m deep), I hope to glean information regarding how this may affect the melting of overlying sea ice.

Currently, the oceanographic models we have for the Arctic concern multi-year ice: that is, perennial ice that is built upon year after year. Now that this is being replaced by seasonal, or first-year ice, which is chemically and physically distinct to the longer-lived variety, the existing models are due for renewal. This cruise is particularly exciting, as data throughout the winter months are rare. Seeing how water masses affect, and respond to, a new first-year ice regime over this 6 month timescale is of paramount importance for the synthesis of more up-to-date heat exchange models.

Polar bear inspecting our (thoroughly displaced!) survey line.
(Image credit: Markus Kayser, AWI)
Working directly on the sea ice comes with its challenges. The Lance has been drifting in a predominantly southwestern direction towards Fram Strait, between Greenland and Svalbard where the majority of wind and ocean currents leave the Arctic. Accompanied by increasing temperatures, ice floe disintegration is a very real occupational hazard. It is a relief to gaze out the window every morning and see our little world still intact, though occasional cracks (or ‘leads’) through the ice threaten to tear our playground apart in a matter of minutes. Hundreds of metres of power cable have had to be hauled back onto the boat on more than one occasion, over where cracks spread, revealing the inky blue abyss of the ocean below.

Then we have the bears. Curious onlookers for the most part, we've managed to avoid any potential run-ins unscathed, thanks to our compulsory bear-guard system (pray that this continues!). Not all our equipment has been so lucky, with chewed cables and scuffed buoys occasionally appearing overnight. Though, with a chance to see these bumbling giants in their rapidly diminishing habitat, I’d still have jumped at the chance to work on the Lance even if it was as the dishwasher!

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This blog is written by Adam Cooper, recent Earth Sciences graduate at the University of Bristol.
Adam Cooper (right)

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