Die Eiskante (The ice edge)

Sea ice seen from Polarstern

I could feel it as soon as I woke up – sea ice scraping against the hull. The ship's motion is different in ice. Rather than rocking slowly side-to-side, we stay completely upright but get lifted up every once in a while. It's like going over a speed bump in your car.

We usually hit sea ice somewhere in the Fram Strait, but never this far south or east. Of the 5 HAUSGARTEN expeditions I've been on, this one falls the earliest in the year, so the ice hasn't had as much time to melt yet. We'll be dealing with ice cover at many of our stations over the next couple of weeks.

The good news about there being a lot of ice this year is that we're more likely to see charismatic megafauna like polar bears and seals. In fact, there were some fresh-ish polar bear tracks in the snow on one of the ice floes yesterday. The bad news (which is what actually matters for research) is that sea ice makes deploying sampling gear more difficult. For example, deploying a lander in an ice-covered area means you might not ever see it again. Landers free-fall through the water column and then free-float to the surface when signaled to do so. If a lander floats up and gets caught under an ice floe, the chances of recovery are quite slim.

So we're adjusting the plan. Anyone who's ever read this blog before knows that improvisation is a staple of marine and especially polar field work. We are constantly planning, re-planning, and sometimes just downright winging it. That was definitely the case today.

We're adding long lines to the landers – kind of like a lander on a leash. Under normal conditions, the lander's metal frame would be completely unattached to anything else. At the depths we're working at, it takes about 45 minutes for it to reach the surface once released from the bottom. That's plenty of time for it to drift under an ice floe. After we add the line, there will be a tether to the lander frame that extends through the water column, essentially shortening the time to surface. The engineers rigged it up so that when the lander is deployed, the floats on the end of the line are at about 50 m depth. Then we send the acoustic signal for the system to release, a section of line is freed from its storage basket on the lander (basically, the leash is extended) and the floats at the end pop up. Once we grab the line, we'll lift the rest of the gear out of the water using the ship's winch. It takes longer to deploy and recover but gives us a much higher probability of success.

The lander in its new configuration

So here's the catch: we're working in the deep sea. My stations are between 1800 and 2500 m depth, so that means we need about 2 km of line for each lander. There didn't happen to be an extra 4 km of line hanging around on the ship, but there was plenty of extra line on the moorings that were already in the water column and had to be recovered anyway. We had to recover a mooring to make a mooring.

Most of last night was spent recovering two moorings from the central HAUSGARTEN station. Normen and his team worked alongside the ship's crew for hours to haul in all the floats, gear, and line. It was actually kind of nice for me, too, because there's almost always biofouling on moorings. These particular ones had been in the water for 2 years, so there was a diverse array of species that had settled on the floats, lines, and instruments. I stood by, forceps in hand, and grabbed a couple of samples before each of the parts was power-washed.

As I'm finishing writing this, my lander is on its way to the seafloor. I give my utmost appreciation to the engineers who re-rigged the system and the ship's crew who stood by for hours in the foggy, cold Arctic to deploy it. I'm glad we were able to figure out a way to work around the ice!