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Archive for the ‘Kaitlin Keegan’ Category

Last summer, several IGERT fellows had the serendipitous and rare opportunity to witness a warming climate’s effect on Greenland first-hand. Julia Bradley-Cook was stationed in Kangerlussuaq collecting data on carbon cycling in soil when the bridge over the Watson river collapsed from anomalously high flows of meltwater (see http://dartmouthigert.wordpress.com/2012/07/11/glacial-melt-threatens-town-water-supply and http://dartmouthigert.wordpress.com/2012/07/11/update-the-river-powers-on). Days later, the 3rd cohort of Dartmouth IGERT students flew up to Summit Camp, Greenland’s highest point, and observed features of the ice sheet-wide surface melt. Fellow Kaitlin Keegan, Thayer Professor Mary Albert, and their collaborators study the frequency of such melt events; their work at the North Greenland Eemian Ice Drilling (NEEM) sight has suggested that such an event last transpired in 1889 and, therefore, is unprecedented in the satellite record. (See http://dartmouthigert.wordpress.com/2012/07/21/new-summit-melt-layer).

A new Nature publication on Greenland climate authored by the NEEM community, which includes Albert and Keegan, prompted an entry on the scientific blog site RealClimate.org. RealClimate was started and is maintained by “working climate scientists” who “aim to provide a quick response to developing stories and provide the context sometimes missing in mainstream commentary.” Check out the discussion on Greenland’s 2012 summer conditions, how they compare to those 125,000 years ago, and what we can learn about past temperatures and sea level rise from an ice core! I was particularly excited about the conclusion of the entry since author Dr. Steig mentioned the significance of a new ice core from West Antarctica. I just returned from a field season on Roosevelt Island assisting with the drilling of this core, which will help scientists understand the sensitivity of the Ross Ice Shelf and, thus, of the West Antarctic ice sheet to changes in climate. http://www.realclimate.org/index.php/archives/2013/01/the-greenland-melt/

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This post was written by Professor Mary Albert

Our NSF-IGERT studies at Summit, Greenland are designed to investigate aspects of snow, firn, and ice core interpretation, as part of our larger look at polar environmental change in Greenland. Coming to the site of the GISP2 ice core, where ice core scientists first realized that climate could change in less than ten years, is a real adventure for our graduate students! Being here now to witness a new change and to measure its effects  — the first significant melt at this cold high-altitude site since 1889 – is but one of the great opportunities to showcase the excitement of working in polar science!  The National Science Foundation has facilitated this unusual and extremely educational opportunity in this brief round of science here at Summit, the very top of the Greenland Ice Sheet.

Our third-year IGERT student, Kaitlin Keegan, came up earlier to conduct snow science with the JSEP group of high school students; she then left Summit before our arrival to venture on to the NEEM site. I have thoroughly enjoyed the honor of leading the discoveries with our first-year IGERT students – what a bright group of PhD students they are!

IGERT Cohort 3 at Summit
The Dartmouth IGERT group at Summit. From left to right: Mary Albert, Stephanie Gregory, Lee Corbett, Jessica Trout-Haney, Chelsea Vario, Alexandra Giese, and Ian Baker

We made stratigraphy, density, and permeability measurements on important layers in the snow.

Steph and Mary looking at Firn Sample
Stephanie Gregory and Mary Albert discuss a snow sample for a permeability measurement.

We collected samples of the refrozen melt layer to take home for more detailed measurements. Hey, even our panda got a taste of ice science!

Panda eating Ice

Being at Summit immediately after the first big melt there since 1889 has been a great science & education opportunity!  We are all very thankful to the NSF IGERT program for supporting these students, the NSF Office of Polar Programs for allowing us to come to Summit, the Air National Guard for getting us to Greenland, and to all of the wonderful folks at CH2Mhill Polar Services for providing superior field support, including the extremely capable camp staff at Summit Station.  A very hearty Thank You to you all!

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I arrived at Summit Station on July 13th, while traveling with the
Joint Science and Education Program (JSEP) for a short visit to the
camp. When we arrived, Summit Station had been experiencing above
freezing temperatures for multiple days prior to our arrival and a
melt layer formed on the near surface snow. I have been studying the
physical properties of the top layers of the ice, the firn, at Summit
and NEEM for my Ph.D. research. Recently, I have been focused on the
melt layers present in both firn cores because they occur very
infrequently. At Summit, there is only one other melt layer besides
the melt layer from this past week and this previous melt layer dates
to 1889.

The most interesting part of being at Summit Station just after a melt
event had occurred, is that the melt layer formation process could be
observed. When studying a firn core, there is only a small cross
section of the firn column that can be examined, which makes it hard
to understand how the melt layer formed and how evenly distributed it
is. Studying snow pits at Summit, including the recent melt layer,
presents a unique opportunity for us to understand how previous melt
events occurred. While at Summit density, stratigraphy, and
permeability measurements have been taken and samples will also be
brought back to the laboratory at Dartmouth, which will give us a clue
about melt layers in the past.

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Travels to Denmark

Hello!

I’m Kaitlin, a cohort 1 IGERTeer, and I haven’t blogged since our 2010 field seminar in Greenland. Since then, I have been busy finishing my required coursework and now have the luxury of focusing solely on research. That research is what brings me back to our IGERT blog. As you may, or probably may not, remember, I study firn in Greenland, which is the 50-100m of snow on top of the Greenland ice sheet (not fern, the leafy plant). I have travelled from Dartmouth to Copenhagen, Denmark, to continue my firn research.

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The Center for Ice and Climate (CIC) is housed at the Niels Bohr Institute of the University of Copenhagen, and is an important research center in the ice coring community. Most recently they’ve lead the NEEM deep drilling project, which generated a new deep ice core in Greenland in record speed (http://neem.dk/). I’ve come to the CIC to work with two firn cores that are stored here in Copenhagen.

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The Niels Bohr Institute

In the next couple of months, I will be taking measurements on these firn cores, which I will compare to the firn measurements I have taken back home at Dartmouth. While here in Copenhagen, I will also learn more about the Danish ice coring community, meet other scientists in this very international field, and learn about Danish culutre. I plan to do all of this without out eating too many of these:

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My nemesis: a raspberry danish.

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Team IGERT helped Kaitlin collect all her data for a snow pit on summit — permeability, density, and crystal size. To find out more about the process, please view our mini documentary.

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At the end of our first day of fieldwork we covered our snow pit with plywood to protect our hard work from overnight snowdrifts. We were all happy to simply brush some snow aside instead of having to dig another pit from scratch.

we covered the pit to protect it from overnight snow drift

The second day was Kaitlin’s day for sampling. She and Gifford are both studying the nature and dynamics of snow layers. Normally, as PhD students, they would each be focused on their own data collection from different pits and at different sites. However, during the  trip planning they realized how much their data complement each others’, and they made a new plan to collect samples from the same pit to align their data sets.

To give you an idea of what snow layers are all about, here’s a picture of snow layers from a back-lit snow pit:
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The layers record snowfall events, the seasons, and other environmental conditions, like wind. The lighter areas are less dense snow, with bigger snow crystals, and the darker areas are more dense snow, with smaller crystals.

Kaitlin is measuring permeability of the snow from the surface down to 2 meters. Permeability is how easily air, or any other liquid, flows through a material, which in this case is snow. A good example of permeability is rainfall on flat ground: rain that falls in a sandbox will flow below the surface, but rain that falls on concrete will collect and form a puddle. This difference is because sand is permeable and concrete is not permeable at all.

Kaitlin explained why it’s important to measure permeability in snow–permeability helps us understand how gases flow between the air and the snow, and then within the snow layers too. This information helps ice scientists interpret the gases that are found in ice cores, like those taken from the Greenland Ice Sheet.

To measure permeability, Kaitlin is using a permeameter, which was developed by her adviser, Dr. Mary Albert, and Frank Perron at Polar Research Solutions. The measurements have to be made in the field so the instrument is portable, but I can tell you that the gray and orange battery cases are not light!
the permeameter measures flow of air through snow

But what does it all do?? Right in the middle of the setup you can see the white cylinder that holds the snow sample. Tubing connects a pump, in the yellow case, to the sample to control the flow of air through the cylinder. The air flows through the snow sample and then to the black case, where meters measure the rate of flow.

It all seemed a bit confusing at first, but Kaitlin and Mary led us through the sampling techniques. Here’s Laura, our geologist friend, adjusting the knobs that control the flow of air through the sample:

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This structure of a stellar dendrite snow crystal that fell at Summit Camp

The coolest part was that we saw that permeability was lowest in the snow surface, where it was wind-packed. The deeper samples were more permeable because the lower layers generally have larger crystals which make for larger passageways for the air to flow through.

We also measured density of the snow. Whereas permeability tells us how much space there is for air flow, density tells us the mass of snow in the layers. Two different samples could have the same permeability but, depending on the crystal structure, they could have different densities. Density is a basic measurement that Kaitlin is taking to help characterize the snow layers and compare them with other sites.

To measure density we used a known volume sampler, and then weighed the samples on a portable scale.

What started out as a cloudy day turned into a calm and sparkly one, perfect conditions for what ended up being a 16-hour science marathon. Kaitlin finished the day with some valuable data and I am coming away with a new-found appreciation for the information that is locked up in these delicate, little pieces of frozen water. Snowflake wonder is knowing that no two snow flakes, nor snow layers, are the same.

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What a surreal opportunity to travel to Summit Camp with our IGERT friends! Kaitlin and I both have been up to the Greenland Ice Sheet before, and it was a decided treat to perform our science with the help of our IGERT cohort. As you’ve read in the blog, which has been thoroughly recording our exploits thanks to a Herculean effort by the rest of the group (including Ross!), Kaitlin studies the material properties of firn and I look at the spatial variability of the ice sheet. Kaitlin has been to NEEM, the Danish deep drilling site, and I have been to Summit Camp earlier this summer. We both agree that while deep field camp science is fun in its own right, experiencing the flat white of the polar ice sheet with your mates is a uniquely special time that will always be remembered. Cheesy? Perhaps, but all together true, and very telling of our experience.

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We appreciated their enthusiasm, willingness to help, and thought-provoking questions. Here were scientists, some totally taken out of their studied element, challenging Kaitlin and I with their transdisciplinary inquiries and forcing us to refine our articulation of our respective fields. We certainly owe them, at the very least, a heartfelt “thanks” for their contribution to our field science experiments.

Cartwheel ... Keegs' one-handed!

Without rehashing the previous days, we found ourselves sad on the last day for obvious reasons: 1) the family we inherited up at Summit Camp whose selfless and tireless daily deeds kept not only the big Summit machine moving, but elevated our group’s morale (i.e. sauna and cookies) as well as helped maintain our tightly-scheduled time at camp and 2) leaving “home”. Not home in the sense that we would have wanted to pick up from Hanover and move permanently to the polar plateau, but home in the sense that it felt natural to conduct our science here; we are very curious about snow and ice, and the draw to the ice sheet is undeniably strong.

IGERT @ Summit

So, goodbye Summit … but not really “goodbye” so much as “see you later.” We will, you see … we’ve promised ourselves that much.

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