The Bowman Lab

McMurdo Sound, right about the time the temperature hit the record low so far for this year. The memorial visible on the hill is Vince's cross, George Vince was a seaman on Scott's first voyage to Antarctica.

It’s a cold one today at McMurdo, we just past the magic temperature of -40… the point where the Celsius and Fahrenheit temperature scales converge (briefly).  This is the temp without windchill, with the windchill it’s a brisk -59 C (-74 F).  I took a brief walk to snap this picture of the sunset and made the mistake of facing into the wind for a few seconds, the tears froze to my face instantly.  I wouldn’t want to be at the ice edge right now (it was much warmer when we were there on Monday), but I bet young sea ice and frost flowers are forming everywhere on the open water. 

We hear a lot about windchills and we’ve all experienced how much cooler it feels when the air is moving past us.  Many people misunderstand the term however.  It’s not that the air is any cooler when there’s wind around, we feel cooler because we’re losing heat so much faster.  This heat loss is what the body registers as temperature.  A piece of metal placed outside at -40 C with a windchill of -59 C will never get colder than -40 C, but it will reach that temperature much faster than on a still day. 

It’s been a warm, snowy year and as a result the sea ice around McMurdo Sound is warmer (and thinner) than usual.  Among other things this has being causing problems for travel over the ice; cracks and weak spots are continually appearing.  Today’s low temperatures, aided by the wind chill, should rapidly cool any exposed ice surface and have a noticeable impact on ice growth and ice strength. 

Update… I just got word that it bottomed out at -42 C, the coldest day of the year so far for McMurdo Station!

Young ice rafted up at the ice edge. The ice floe that we ultimately sampled is on the right. This photo is looking south toward the land-fast ice, you can see Mt. Discovery in the background.

Yesterday we finally made it out to where we can sample frost flowers, retracing Dan and Ryan’s track from Saturday out to Cape Royds.  We were stopped from reaching the ice edge itself by an abrupt transition from ice over one meter thick to ice only 50 cm thick.  In reality this is plenty of ice to support the weight of our vehicles, but McMurdo Station rules prevent vehicle travel on ice thinner than 76 cm (30 inches).  So we parked our vehicles, shouldered packs, and headed to the ice edge to see what we could find.  To understand what the ice edge looks like right now it’s necessary to understand the weather conditions over the last several days.  We had an intense period of wind blowing primarily from the SE, followed by a couple of nicer but cool days, and finally a day of mild but persistent north wind.  Yesterday was absolutely beautiful, possible the nicest day since we arrived.

Sampling frost flowers is as easy as scraping them from the ice surface with a clean shovel into a sterile plastic bin. Photo: Shelly Carpenter.

The period of strong SE winds cleared the ice edge of any recently formed ice, leaving an abrupt line between thicker, land-fast ice (ice that is anchored to the shoreline) and open water.  In the open water ice still would have been forming, but the wind would have quickly driven this young ice out toward the open waters of the western Ross Sea.  Once the SE winds ceased ice would have formed in place, some of it attached to the land fast ice and some of it drifting freely.  Sunday’s mild north wind would have driven all of this ice south, against the thick land-fast ice.  With nowhere to go this young ice would have “rafted up”, with some floes getting pushed underneath others.  Think of a much scaled down version of the plate tectonics that gives rise to ocean trenches and mountain ranges.  This is what we found at the ice edge yesterday. 

Sampling the young ice underneath takes a little more effort, but the work still goes pretty quick. Photo: Shelly Carpenter.

A young ice flow that is rafted on top of another flow will quickly drain of salt, and presumably of many microorganisms.  As a result this ice is of limited use to us for our current study.  Fortunately we were able to find a large pan of young ice that had not rafted.  Had the north wind been stronger we might not have found anything suitable in the area.  Like all of the other floes we observed this one was completely covered with very salty several day old frost flowers.  We did a quick check of the salinity of the frost flowers, the whole field was almost three times the salinity of seawater.  Bacteria generally get transported with salt in sea ice.  More salt means more bacteria, so this was perfect!  We trekked back to our vehicles to collect our sampling gear and get to work.

This is a profile of the young ice that we sampled, with the top of the ice on the right and the bottom of the ice on the left. The growing ice front, or bottom horizon where the ice is adding thickness is defined by the white band. Below the white band frazil ice is accreating to the underside of the ice. As ice continues to accreate the band will move steadily downward driven by the movement of the freezing point lower in the ice column.

It didn’t take us very long to collect perhaps 500 kg of frost flowers, young ice, and water.  It took much longer to haul these samples 2 km back to the vehicles.  We had counted on being able to drive much closer to where we wanted to sample so we only brought one small sled for hauling.  Not nearly enough unless we wanted to make a half-dozen trips!  So we improvised a sled from a plastic containment berm that we use when fueling our saws and drills in the field.  Not ideal, but it got the job done.  However there are sore legs and sore backs all around this morning.  Many thanks to Dan and Kevin (who volunteered to go out with us yesterday), we couldn’t have done it without them!  We packed up just as the sun was setting and got back in time to eat a late dinner before turning in.  This afternoon Shelly and I will begin the much longer process of melting and filtering all of this material and sorting out our field gear for the next excursion…

Putting our backs into it. Dan and I reenact some of the finer scenes of Antarctic exploration in an effort to get our samples back to the vehicles. Photo: Shelly Carpenter.

After some initial seal related frustrations we were treated with a spectacular Antarctic day. It's a little difficult to make it in this photo, but at one point we got a beautiful double "ice-bow". The source of the ice-bow is the same as a rainbow, except that ice crystals not water droplets are causing the refraction. You can make out the large red splotch where the seal left one of his or her many markings on around our old pool.

I said it was good to have a Plan C as well.  Sunday’s normally a day off at McMurdo but after breakfast we headed out to check on our not yet complete frost flower pool and to see if we could get a little further on removing all the ice from it.  Unfortunately it was immediately apparent on arriving at our site that we’d have to abandon Plan B.  The seal that we had seen nosing around the day prior had clearly claimed our pool as a hang out spot, with a neatly maintained seal hole in one corner of our pool.  That alone wasn’t a huge problem but seals are pretty messy animals.  Like other aquatic creatures they aren’t too picky about when and where they relieve themselves.  Seal holes are usually pretty well marked with fishy pink excrement and this one was no exception.  In fact this particular seal seems to have gone above and beyond the norm in this case.  From a microbiological standpoint the pool is irrevocably contaminated even if we could get rid of the seal, which we can’t.

Our intrepid volunteer for the day Sandwich (neither Shelly or I got the backstory on her nickname) gets ready to drill some holes in our new pool.

It was however, a beautiful Antarctic day and we didn’t want to waste it.  We quickly hatched Plan C, which was to dig a pit about half the thickness of the ice and then drill a couple of small holes all the way to the bottom.  This shouldn’t look that attractive to a seal as a breathing hole and should give us some frost flowers.  The downside is that this sort of pool isn’t going to circulate as well as a pool with an open bottom.  I don’t know exactly what this would mean for the marine microbial community that might ultimately end up in the frost flowers, but it might not exactly represent a natural situation.  But then again it might be good enough.  If we are unable to sample natural frost flowers a few such pits (if they work) might get us the samples we need.

And here's our new seal-free pool starting to freeze over.

Fortunately the chance to get some natural frost flowers has never looked so good!  Dan’s long scout with Ryan, another McMurdo staffer on Saturday was pretty successful.  Maneuvering around cracks and thin ice they were able to get to Cape Royds.  Enroute they past some small leads chock full of frost flowers.  Even better from Cape Royds they were able to see the ice edge, with large expanses of young ice leading to open water.  Although they didn’t get out on this young ice it has a whitish look that suggests it is covered with frost flowers.  With luck we’ll be on our way up there early tomorrow, pending approval from the McMurdo Station managers and good weather…

First glimpse of an Antarctic frost flower, from Dan and Ryan's trip to Cape Royds on Saturday. Photo: Ryan Wallace.

With a little help from McMurdo fleet operations Plan B is a go!

After one day I’d say we’re about a quarter of our way through our execution of plan B.  A crew from McMurdo fleet operations came out and drilled a series of overlapping 4 foot diameter holes in the ice for us (check out video here).  Combined this gives us a “swimming pool” in the ice that’s about 12 feet long (4 meters) and 6 feet wide.  The downside to using an auger to make holes in the ice is that no ice is actually removed from the hole during the process.  When the operation is complete your “swimming pool” contains the remains of 1.5 x 4 x 2 meters of ice, or 12 cubic meters.  Sea ice weights about 900 kg per cubic meter, so that leaves 10,800 kg (24,000 lbs) of ice to remove from the hole!   A lot of this is slush and small chunks that can be removed with a shovel or a pool skimmer net over time.  The remainder is in very large chunks that can’t be pulled out.  We tried anchoring ice screws in these ice boulders so that we could pull them out with the Pisten Bully, no luck!  The only way to deal with them is to chain saw them into small, manageable pieces.  With the chainsaw spraying cold seawater everywhere and the sides of the pool very slick with ice this is cold, dicey work.  Shelly and I had to take frequent breaks to eat (primarily chocolate, a favorite field food for both of us) to keep our energy and spirits up.  I got so iced up that I couldn’t sit in the Pisten Bully during these breaks, the cabin was too warm and my pants would start to melt!

Drilling holes in the ice is easy. Clearing all of the ice from the holes after they're drilled is hard. We tried using the Pisten Bully to haul the big chunks away.

We called it a day when we ran out of glycol to lubricate the chain on the saw (we can’t use chain oil because it would contaminate our site).  With sore arms and sore backs I think we were both ready to call it quits regardless!  Before we finished the seals had already found our hole, which could be a big problem with this plan.  We anticipated this but I was still startled when there was a loud snort from the hole.  Turning around we saw very large nostrils poking through the slush.  This particular seal hung around for quite a bit, and was not even

When that didn't work we had to resort to cutting up the partially submerged large chunks of ice. We made a dent, but we still have a long way to go!

deterred when we resumed sawing on the ice just a few feet away.  The seals in McMurdo Sound are quick to capitalize on any opening in the sea ice as a place to haul out and rest and they are pretty adept at maintaining openings.  We need our pool to freeze, so if the seals decide they like it we might have a problem.  At any rate we’ll be back out tomorrow continuing our ice removal efforts (unless the weather turns!).  And we have some help.  Sunday is usually a day off for staff at McMurdo, but a couple of hardy volunteers have agreed to spend their day off mucking out chunks of ice with us.  A few more days of work and we might have our first frost flowers…