Spring Field Work

My work during the spring field season with the Norwegian Polar Institute started in Longyearbyen in mid-April.  After waiting a few days, Dr. Kohler and I departed for Kapp Linné to do a mass balance study on Linnébreen.  We snow mobiled from Longyearbyen to Isfjorden Radio, a trip of around 100 km.  Isfjorden radio used to be the main point of contact between Svalbard and mainland Norway and still has a variety of antennas.  Now it serves as a tourist destination serving excellent food and offering a place to stay and an otherwise uninhabited area.  During our trip there and during the first day of field work weather was excellent and we were able to take GPS velocity measurements, stake measurements, density measurement, snow soundings, and drill one new mass balance stake.  The second day the weather deteriorated and we took some more snow soundings, density measurements, and collected one snow sample to analyze for pollutants.  Though the weather on the trip back was now as good and visibility was at times quite poor, with the aid of handheld GPS units we were able to make it back to Longyearbyen without incident.   After repacking our gear and stowing the snow sample in a freezer, we headed to Ny-Ålesund the next day. 

 

After one day of preparation in Ny-Ålesund, we planned to head to Kongsvegen, a larger glacier located at the end of the fjord.  Due to the fact that there was no sea ice this year, which although unusual is not unprecedented, we had to drive a somewhat circumspect room over another glacier and through a pass to approach the glacier on the other side of a peninsula where it can be accessed via land.  When leaving that morning it was raining, something unusual for late-April weather in Ny-Ålesund, but the snow conditions seemed passable so we pressed on.  On the other side of the pass, the entire drainage delta of another glacier had turned to slush making it very difficult to drive and we were forced to turn back after one of the most experienced drivers on a very powerful snow mobile said that he didn’t think that it was prudent to continue.  During our drive there, the snow conditions on the pass had deteriorated.  We had a lot of difficulty getting the snow mobiles and equipment back up the pass.  One snow mobile couldn’t even make it up the pass without a sled and had to be driven around the peninsula.  After returning, we were forced to reconsider our field plans and realized that the trips to the large glaciers of Holtedalfonna and Kongsvegen would have to be limited to the essential measurements, namely mass balance, unless cold weather returned.

The next few days I spend working on Midre Lovénbreen on a variety of different projects including borehole logging, ground-penetrating radar, ice coring and mass balance.  When borehole logging we used neutron probe to measure density and compared it to the bulk density of an ice core drilled in the same core or nearby.  The neutron probe contains a radioactive source which sends out neutrons.  They scatter off water inclusions in the ice and the number returned indicates the density.  I didn’t directly operate any of the borehole logging equipment but it was interesting to watch.  For the first time I did help extract an ice core.  We drilled to approximately 7 meters to compare with the borehole logging that was done in a smaller hole nearby and then logged the drill hole as well.  The drilling was a new part of field work and it was interesting to operate the drill as there is some technique to make sure that the drill bites but doesn’t get stuck.  You don’t want to have to dig it out when it is 20 feet into the ice.  We also operated radar systems in the area where we conducted borehole logging experiments and extracted ice cores.  This allows us to get some spatial coverage of glacier structure instead of only knowing the properties at one point. 

Eventually, the cold weather did return and was accompanied by a snowstorm.  The next day a group immediately went to Kongsvegen to conduct experiments and was successful in conducting borehole logging, shallow ice coring, mass balance measurement, and snow sample collection.  Although this was not the experiments were conducted to the same extent as originally planned, this was valuable data and gave people something.  Following this trip we continued mass balance measurements on Midre Lovénbreen and Austre Brøggerbreen which are two glaciers that are very close to Ny-Ålesund.  Due to the warm temperatures both in April and January we suspected that water had percolated through the snow pack and refrozen forming what is called superimposed ice.  The superimposed ice has a positive effect on the mass balance but it is difficult to measure due to the fact that you can’t easily tell the difference between superimposed ice and the glacier surface when snow sounding.  Therefore we took very shallow ice cores drilled by hand at various points on the glacier to characterize superimposed ice accumulation.  The variation from superimposed ice to the previous summer glacier surface is shown by a dirt layer followed by ice that has a different texture when we examine the shallow core.  Taking these measurements revealed superimposed ice accumulation of up to 20 cm.  This was a very large accumulation and it is easy to see how superimposed ice can play a significant role in mass balance.  After one more abortive attempt to reach Holtedalfonna in my 3^rd week in the field it was clear that it was no longer possible.  Another period of above freezing temps, which normally first come in early June and not mid-May, made it clear that it would no longer be possible to reach the glacier.  Therefore I was not able to collect additional radar data for my research on the firn lake on Holtedalfonna.  Nevertheless the field season was an excellent experience which allowed me to see many new aspects of glaciological experience and to gain important experience operating in the field. 

 Enjoy all the pictures below. 

 Isfjorden radio on a stormy day.  Notice the large number of antennas still presnet.

A density pit on Linnébreen.  Snow samples are taken vertically and weighed to measure density. 

 Jack Kohler surveys Kjell Arild’s snow moblie which sunk in the slush.  (Photo: Rune Storvold).

Borehole logging on Midre Lovénbreen.  The tent protects the sensitive electronics. 

High frequency radar experiments on Midre Lovénbreen.  (Photo: Bob Hawley)

Me operating the ice drill on Midre Lovénbreen.  (Photo: Bob Hawley)

The GSSI ground-penetrating radar field computer. 

The GSSI ground-penetrating radar 900 Mhz antenna.

Me drilling by hand for superimposed ice.  (Photo: Elisabeth Isaksson)

A very shallow ice core showing superimposed ice as the denser ice at the bottom of the core.  A dirt layer clearly marks the boundary between the superimposed ice and glacier ice from the previous summer surface.   

The calving front of Kronebreen, the fastest moving glacier on Svalbard.

Austre Brøggerbreen from a distance showing a large meltwater stream in the middle of the photograph which we had to cross on snow mobiles.

Work at the Norwegian Polar Institute

            Now that Christmas is over it is time to get back to work again.  I am starting work at the Norwegian Polar Institute (NP) in Tromsø.  Moving to a new place is a little hectic and stressful but things how calmed down now and I have started to work on my new project: calculating englacial water content of Holtedalfonna on Svalbard.  As this work is ongoing and I have just started, this entry will be a brief overview of using radar-echo sounding data to image glaciers. 

            Glaciers, like trees, have annual accumulation layers.  The layers are formed by snowfall that falls each year and which eventually is compressed to ice due to pressure from the new snow above it.  Each layer of accumulation, one year of snowfall, thins and spreads out from the weight of the new snowfall.  Additionally, due to gravity, glaciers flow.  Although we generally think of ice as a solid, it is relatively close to its melting point on Earth and therefore behaves quite similarly to liquid in many cases, only on a longer time scale.  We see that the ice flows like a liquid when we measure the stakes on glaciers that were allowed to sit over a winter.  They have moved, often at different rates, showing that different areas of a glacier move with different speeds.  When examining glaciers or ice sheets, such as those on Greenland and Antarctica, we can see annual accumulation layers and identify properties in them.  As the ice is compressed and flows the layers deep down become thinner than those on the surface and interpretation becomes more difficult, instead of dealing with a foot of ice as representative of one year, we may be dealing with centimeters if ice or less as representing one layer.

            Ice cores are usually used to examine the annual layers.  We drill into the ice and pull out a core that contains layer upon layer of ice.  Bubbles of air, and if there is more pressure ice-air clathrates, trapped in the ice give us a picture of the atmospheric composition in that accumulation layer and therefore at a definite time in the past.  Furthermore, radioactive isotopes and volcanic dust provide us with dates on layers that can confirm our interpretation.  A core is, however, a picture of the ice in one place.  We can only be sure of our conclusions where the core is drilled and thus have a picture of the history of the ice sheet at that one spot.  This is where ice-penetrating radar comes into the picture. 

            When operating ice penetrating radar we place a radar transmitting antenna and receiving antenna on the ice surface.  The light waves are then transmitted into the ice.  Each layer has slightly different dielectric properties and therefore acts as a lens with a slightly different characteristic.  The reflections from these ice lenses, representing annual accumulation layers, are clearly visible on a radargram, a visualization of radar data.  If we take radar data where a core is drilled we can quickly extend the results from a core several hundred kilometers across an ice sheet and give a large-scale picture of past climate.  Furthermore, radar data allow us to examine dynamics inside a glacier.  We can see cavities, conduits, water, and the ice-bedrock interface using radar since the optical properties of these objects are different.  Furthermore, we can also see the dynamics of the ice.  The bending of layers conforming to bedrock topography is visible.  We can also see stress and strain in the ice layers.  Radar data thus gives us a much more complete picture of the internal workings of an ice sheet and is unique in that it can image large areas of the ice sheet easily without a large amount of bulky equipment. 

            My specific project is looking at radar data from a glacier called Holtedalfonna on Svalbard.  I will calculate and spatially map the englacial water content.  This work is just starting and pictured below is some radar data with several digitized layers. 

Click on the image for a larger version.

An example of interpreted radar data from a glacier.