Live Science: What is it like to drill sediment cores out of a
Tim Hodson: It's a
race against the clock.
Our field season is tightly constrained
by weather and flight availability. On top of that, we have to
work quickly while the borehole is open, to deploy as many
instruments as we can. Once the borehole starts to collapse
(squeezing shut under the weight of the ice), we have to spend
precious time and fuel to open it up again.
We're left with
almost no margin for error with the more complicated
experiments. Not only are we working full tilt, in an
unforgiving environment, but we only have one shot to get things
It's exhilarating, almost like being in a pit crew or
crewing a sailboat during a race.
Live Science: Walk me through what this lake looks like.
were to peel the ice off, what would you see?
Hodson, a doctoral student at Northern Illinois University,
holds a core
of sediment drilled from Subglacial Lake Whillans,
a lake buried
deep beneath the West Antarctic Ice Sheet.
Scherer, Northern Illinois University
Hodson: Much like
on land, the bed of the ice sheet is a patchwork of different
There are lakes with different types of waterways
connecting them, and areas where the ice sheet is frozen to the
bed. I sometimes think of the ice-sheet bed as a wet desert
desert in the sense that melting beneath the ice sheet only
supplies a small amount of water, perhaps the equivalent of a
few centimeters of rain per year.
However, as there's
no evaporation and little freezing, much of the bed remains wet.
Consequently, the Antarctic's
subglacial hydrologic network is typically slow-flowing and much
less powerful than the rivers we're familiar with on land. This
Greenland, where melt-water forming at the surface flows down
to the bed
through big, fast-flowing conduits.
As it turns out,
the abidance of water is extremely important to how the ice
flows. If there's no water, the ice sticks to the bed. A little
water lubricates the bed, allowing the ice to flow quickly.
add more water, and conduits start to develop, which drain the
bed so efficiently that it starts to lose its lubricating
Live Science: Were you surprised by any of your findings?
Hodson: I think
everyone expected the subglacial lake sediment to be similar to
the sediment in a regular lake on land.
In hindsight, that seems
a bit naïve, but that's the nature of working in an unexplored
environment. As it turned out, subglacial lake sediments - and
subglacial Lake Whillans, in particular - pose a number of
For example, many standard techniques, like
dating, don't work under an ice sheet.
In the end, we addressed
the big questions we were after, but not in the manner we'd
expected. It required a bit of creativity from the team, but
that's part of the fun of
Live Science: What did this study tell you about how the ice
learned a great deal over the past few decades about how the ice
flows, from satellite and aerial remote sensing.
theoreticians have been hard at work trying to explain how
processes at the ice-sheet bed affect the ice flow above, but
some questions can only be answered by directly accessing the
This work will help refine our theories about how the subglacial hydrologic network works, which, in turn, controls
how the ice flows.
We still have a lot to learn about
why the ice flows the way it does. We don't yet understand why
the ice flows the way it does in this region, but our
observations will hopefully help to fill in the puzzle.
Live Science: What, if any, are the implications for climate
change and sea level rise?
section of the borehole drilled into Antarctica’s subglacial
is about 0.5 meters (20 inches) in diameter
corrugations due to turbulence during melting.
Credit: Dr. Alberto
funded by NSF and NASA.
Hodson: We don't
really know yet.
For example, our work suggests the ice sheet is
more sensitive to sea level rise than previously thought.
Shrinking ice sheets raise sea level, which, in turn, causes ice
sheets to shrink further.
Realistically, other mechanisms, like
ocean and atmospheric warming, probably have a bigger impact on
the ice sheet than sea level. But in order to make accurate
models, we need to put constraints on all of the processes that
potentially affect the ice sheet.
Especially when we're trying
to forecast how the ice will behave over the coming decades to
centuries, even these less important processes become
Think of it like compounding interest: A few percent
interest won't grow your investment overnight, but accumulated
over a couple decades, it has a big impact.
How do you integrate information from studies like this into
400 lakes under the Antarctic ice sheet, do
you need sediment studies like this on all or many of them to
start to build accurate models, or can you extrapolate from a
Integrating this sort of observational data into a model is a
process of trial and error.
Basically, it's up to the modeler to
choose which processes to include in their model and how best to
represent them. Oftentimes, we don't fully understand all the
physical laws working in an environment, so we have to give our
This is true in almost all cases, so we need
observations to help us assess whether our model is sound.
present, there's still a lot we don't understand about the
ice-sheet bed, so we do want more observations. We certainly
don't need to go drilling into every lake, but there are a
number of big scientific questions that can only be addressed by
accessing a few lakes in particular.
The big question driving
this project was just to get a first glimpse at the microbes
living beneath the ice sheet and to understand how they survive.