Talk of the Town: The Case of the Missing Sea Ice

I'd imagine you are curious about the gossip around town. A couple weeks ago, most conversations in the halls were about wildlife - who'd seen what and where to find them. These days, there are two subjects floating in the halls - the cargo ship and the sea ice.

Remember a few posts ago when I wrote about the cargo ship that had come to deliver goods for the next year and to take away trash and old equipment? Well, it's still here. For several days, large areas around the galley were blocked off and filled by boxes with labels like "Frozen Mixed Vegetables" and "Frozen Chicken" and "Frozen Whatever." (Yeah, I made that last one up.) It was strange to see boxes of frozen things just laying outside under the sun, although, of course, we are now well below freezing. Those areas have since been cleared of boxes and reopened to foot-traffic, so I'm guessing the process has transitioned from unloading to loading the ship. The cargo ship has been in town for a while now, so it's not such hot gossip anymore, but it's so important that it still seems to occupy people's minds. Also, we're getting a little more variety in the galley now - boiled unseasoned cauliflower instead of just boiled unseasoned mixed veggies. Yay?


But, the real topic of conversation is the sea ice - or now, the lack thereof. First, a little background:

USGS map of Ross Island with approx. location of permanent ice in grey, 

transient sea ice "shelf" in darker blue, and open water/discontinuous sea 

ice in lighter blue.  McMurdo and Scott Base stations are on the tip of the 

long, thin peninsula extending S-SW.

McMurdo Station is on an island, which is "permanently' (in human time-scales) attached to the continent by a "permanent" ice shelf (shown by darkest grey-blue on map). McMurdo and Scott Base are on the tip of a long, thin peninsula that extends along the boundary of the ice shelf towards the south. There is a large amount of sea ice that forms in the winter around the stations, some of which is not solid and continuous (lightest blue) and some of which forms a solid shelf during the winter but which melts to varying degrees in the summer (medium grey-blue on map). This transient portion of the ice shelf is strong and solid enough to support an ice runway for the beginning of the season. (I landed there on my first trip to Antarctica in November 2012.) But, by mid-season, enough of the transient shelf has melted that flights are moved to a runway, called Pegasus, on the permanent ice shelf - about an hour's drive away.

Scott Base (NZ) - completely free of the sea ice, with the 

ice shelf edge in the background.

How much the sea ice melts away, and how quickly, varies from year-to-year, but observing the changes at Scott Base is a good measure because it lies just seaward of the boundary with the permanent ice.  They claim to be 98% iced-in.  (You can even buy a t-shirt advertising this!)  Well, this year, Scott Base broke completely free and clear of the sea ice - and then some.






Every year, the transient shelf breaks up in front of McMurdo, which is important to operations, since many supplies are brought in by ship (i.e. the hot topic of the cargo ship).  This usually happens in late January/early February and is assisted by an ice breaker.  In years past, other countries' ice breakers were used, but this year, the newly recommissioned US Polar Star took on the job for its first mission after dry-dock.  But, the crew of the Polar Star said there actually wasn't much for them to do as the ice was already breaking up.  A couple days after they showed up, a windy night came through and blew the remaining chunks of ice out to sea, clearing McMurdo sound early and leaving them with not much else to do.  They say they are now just waiting around for the last ship to leave as it is their job to escort them through areas that may have ice (even if there's not actually ice at the moment).  Experienced McMurdo citizens started commenting on how early the sea ice had cleared out this year.

Following the overnight clearing of McMurdo Sound, there were several days when sheets of ice would appear and disappear along the shores.  This time period was actually quite lovely at McMurdo.  It seemed to be concentrating the animals in certain areas, which made for great wildlife viewing.  (Don't know whether that was real cause & effect, or just coincidence, though.)  But it was also lovely to go to the seaside and watch the rafts of sea ice that had broken away closer to the ice shelf and had drift close to McMurdo's beaches.  The wind moved them from location to location pretty quickly, so it was alway different and you could watch them shift around in the waves and wind as you sat.  These rafts looked delicate and ephemeral, but when the wind bumped them into each other, the crunching made it quite apparent just how much ice mass was there.  The sound of the water splashing on them was haunting.  It also kind of sounded like something from a white-noise CD.






Within the past 3-4 days, though, reports started coming in that the sea ice was breaking up around Scott Base.  This was unusual!  People who had been coming for many season had never seen this happen!  What would happen to road to Pegasus, passes right by Scott Base?!? Would the ice shelf start to break up?!? (Exclamation marks indicate just how exciting and gossip-worthy these topics were in the halls.)

 

And now, it is clear, the ice is starting to break up even on the permanent ice shelf.  No longer are delicate-looking ice rafts drifting past McMurdo.  Now, full-on thick chunks of icebergs are floating out to sea.  When flying into town on Monday, we saw this iceberg breaking off from the shelf.







A few hours later, we saw it floating away through McMurdo Sound.

We also saw cracks forming deep into the shelf, like this one.  These days, the gossip is about what will happen to Pegasus - the runway - if this breakup continues.  Will we all be stuck here?!? Will we have to wait for a ship?!?  Even if the breakup doesn't go that far, how will we get to the air field if the ice road breaks up?!?