A Year of Marine Observations in the Wandel Sea (NE Greenland)
The following piece written by Sergei Kirillov and Dave Babb, CEOS:
In April-May 2015, researchers from CEOS performed the first ever oceanographic and ice/snow survey over the Wandel Sea, in Northeast Greenland. We were based at the Villum Research Station which is located at the Station Nord military base (the story can be found here: http://umanitoba.ca/faculties/environment/departments/ceos/outreach/1293.html ).
During our stay, we deployed co-located ice mass balance buoys and ice tethered moorings at two positions on the multiyear landfast sea ice and left them to operate for one year. Collectively, this equipment measured the seasonal changes in temperature, salinity and currents beneath the ice, ice growth and melt processes, and various surface atmospheric variables (air temperature, pressure, winds and snow depth).
In April 2016, five of us from the Arctic Science Partnership (Sergei Kirillov, Dave Babb, Igor Dmitrenko, Cris Seaton, and Kunuk Lennert) returned to Station Nord to retrieve this equipment, download the data, swap out the batteries and re-deploy the systems to continue the time series for a second year.
When we arrived at Station Nord on April 2, it was below -30 C and the sun was up for most of the day, but fortunately for us there was less snow than last year. Because there were only five us up there this year we were able to work on the ice every day and run a fast and efficient field program. Though the leadership and logistical support from Kunuk Lennert (GCRC) really allowed us to operate like a well-oiled machine and get the most out of our stay at Nord.
What should you know about the sea ice over the Wandel Sea? First of all, if you are going ice fishing there you need to bring a longer auger to get through the 3m+ of sea ice and a strong back to shovel away the 1m of snow. Though once you’ve shoveled the snow and drilled through the ice you may not be that successful because there is very little light available in the water, which limits biological activity from taking place under the ice. This is bad for the biologists, but the lack of solar energy penetrating the ice in combination with the northern latitudes means that the melt season is very short. As a result there isn’t much ice melt during summer and while the 1m thick first year sea ice typically melts out, the thicker multiyear ice doesn’t melt out and remains stable enough during summer to support our equipment.
Now it’s great that the multiyear ice remains stable through summer, but it also makes retrieving equipment that is frozen into 3.5m of sea ice very difficult. None of us had ever retrieved equipment through this much ice, we had deployed equipment through thick ice before but drilling one hole to drop a CTD or a line through is very easy compared to what we were attempting to do.
Our equipment is either attached to a rope or installed in a PVC tube that is anchored on top of the ice and runs through into the ocean below. The goal is to free the line or tube from the ice without nicking it with the auger and not punching through the bottom of the ice until you have all of your drills holed because the second you punch through the ice the entire area floods, likely soaking a few boots and making drilling even that much more difficult.
After shoveling out a 3m diameter snow pit around the mooring lines we began drilling. Our approach was to drill each hole 1m at a time so that we could break the ice bridges that exist between the holes and clear the holes while keeping everything dry.
After drilling we used axes, hammers and mallets to smash the ice bridges and small shovels or our hands to scoop out the ice chunks and shavings. We’d then add another flight to the auger and go down another meter. It wasn’t the fastest method but it worked and we found that the “pit”, as we affectionately called it, was warmer than the air and provided a nice break from the wind.
Once we finally got to the 4th auger flight we would punch through the ice, because of the water pressure the auger would jump up and the hole would fill with salty seawater within a few seconds. We would then begin the difficult and frustrating job of trying to drill the remaining holes and saw out the remaining ice bridges. Visibility down the hole was poor so you couldn’t always see where the ice was still present, but after drilling, sawing and poking with some long steel poles the ice would finally release and the line or tube would pop up.
Tired and cold, seeing that ice finally release and the line/tube rise to the surface was absolutely relieving. But even better was when we pulled up the equipment and saw that it was first of all still there, and secondly still working! Leaving equipment out for one year of continuous work can be nerve-racking, but when it works it’s beautiful!
In total, it took us five days to recover two moorings, the CTDs, ADCPs and ice tethered profiler all worked well and collected an amazing dataset! All the records are still to be processed and scrupulously analyzed, but we can report already that a full one year long time series of oceanographic/ice/atmosphere records has been successfully obtained in this region for the first time ever.
To extend our understanding of local physical processes, we additionally deployed one new mooring ~50 m off the Flade Isblink glacier terminus before we left. Two acoustic current profilers and an ice-tethered CTD profiler will provide high resolution observations on the thermohaline conditions along the front of the glacier and capture the release of freshwater over the course of the year. We also deployed a time-lapse camera at this mooring site that will provide observations of calving events that may be related to fresh water releases observed below.
The equipment is back out on the ice and in the water for another year of sampling, we’ll return next year and do the same thing, but we’ve proposed to go back in May when it’s a little warmer.