Our sampling and deployments have been moving along rapidly! Suddenly we are over halfway through the science operations for our cruise. Here are some highlights from recent operations!
We’ve seen some amazing weather in Andvord Bay with clear blue sky, warm shining sun, and glassy calm water.
Of course most of the days have had temps hovering around or below freezing, snow or rain, and overcast skies proving to us that the weather of the West Antarctic Peninsula is highly variable. Sea ice and icebergs move quickly and conditions can change quite rapidly. We’ve seen katabatic winds suddenly intensify to over 70 knots (hurricane force)! This means that we must constantly be aware of ice conditions and change our sampling plan if there is too much ice to safely conduct an operation. The West Antarctic Peninsula is known for having variable weather as westerly winds bring warm, moist air from the Pacific Ocean to meet dry, cold air masses moving over the continent. This is also what causes major differences in climate between the West Antarctic Peninsula and other portions of the Antarctic continent, further emphasizing the interest in this region in the face of global climate change.
The ice cooperated with us long enough to deploy all of the physical oceanography moorings, weather stations and glacier cameras. The last camera was installed recently in the inner basin of Andvord Bay. The physical oceanography/glaciology team donned climbing gear and zipped away in the Zodiac to assemble this camera on a rocky outcrop facing the termini of a two massive glaciers at one head of Andvord Bay.
This camera will take photographs of the glaciers to assess calving rates, snow cover and melting rates. These parameters will help constrain the ice flux into the fjord and the overall movements of the glaciers. This affects the amount of freshwater and sediment entering the fjord, which in turn influences the productivity (bringing the micronutrient iron) and animals on the seafloor. The ice hasn’t always been on our side, however. We discovered a shallow mooring that we deployed 2 weeks five kilometers down fjord – the entire mooring (including 1200 lbs of railroad wheels) had been dragged >5 km by an iceberg and released in shallower water!
The benthic ecology team assembled a time-lapse camera mooring which will be located in the middle basin of the fjord. This camera is designed to take images of the seafloor four times daily for the next four months; we will then recover the camera, swap batteries and redeploy it for the remainder of the project.
The images will reveal rates of animal activities (e.g. moving, feeding) and responses to seasonal food inputs such as sinking krill carcasses. The camera mooring was deployed smoothly and safely. 15 minutes later voices came over the radio saying there was a mooring mast that just rose to the surface nearby unexpectedly. The radio beacon identified it as the camera mooring which had just been deployed.
The team and ship’s crew quickly put a recovery plan together. The ship positioned alongside the mooring which was grappled and carried down to the stern to be lifted onto the ship. Once onboard it was clear that one of the acoustic releases had failed, but how it had failed was less clear. The weight which had been attached to the releases was obviously gone but the release which dropped the weight was still in the locked position. How could this be?! The team removed the release, opened it up and discovered that it had leaked. The pressure experienced by the release during its descent had forced water into the housing and shorted the electronics, causing it to release the weight without receiving the acoustic signal. Not what we expected! It was a great lesson in working with moorings and a reminder of the risk we take with our equipment to get the data we need. The team later mounted a new release and redeployed the mooring; it is now remains on the seafloor happily collecting data!
Written by Amanda Ziegler.