Student Project: GPS Surveys on the Juneau Icefield

2015 JIRP Student Project: GPS Surveys on the Juneau Icefield

Faculty experts: Scott McGee, Surveyors, Shad O’Neel, Allen Pope.

Overview: The primary purpose of the GPS survey project is to measure the surface velocities 

and surface elevations of the glaciers on the Juneau Icefield. The GPS project also provides 

GPS support for other JIRP research projects, as needed. Collected GPS measurements are 

evaluated against previous years’ GPS records to determine spatial and temporal changes in 

the morphology and behavior of the Juneau Icefield’s glaciers.

Level 1 students will learn the basics of GPS and will participate in collecting GPS survey 

data. They will learn how to set up a differential GPS system and will operate a rover GPS to 

collect data on one or several standard survey profiles. Level 1 students’ involvement will be 

limited to the summer field season and they are not expected to perform advanced analysis of 

GPS data nor compile a student report related to their GPS work.

Level 2 students will be exposed to the same aspects as Level 1 students. In addition, Level 2 

students will form the core GPS team, which entails going out on GPS surveys daily 

throughout the summer field season. Level 2 students will learn and perform detailed 

analysis and presentation of GPS data. It is expected that Level 2 students will compile a 

group report of their summer GPS field work, to be turned in near the end of the fall 

semester.

GPS Projects: Following are GPS projects that will be conducted during JIRP 2015:

A. Surface Velocity. Transverse profiles on the Taku Glacier system will be surveyed 

multiple times in order to determine surface velocity and direction of movement

(Levels 1 and 2). Results will then be compared with data collected in previous years 

to determine if, and where, changes in the flow regime have occurred (Level 2).

B. Surface Elevation. Transverse and longitudinal profiles on the Lemon Creek Glacier 

and the Taku Glacier system will be surveyed in order to determine surface elevation

(Levels 1 and 2). Results will be compared with data collected in previous years to 

determine if, and where, changes in the surface elevation and gradient of the glaciers 

have occurred (Level 2).

C. Strain Rates. Profile 4 on the Taku Glacier is comprised of two parallel lines with the 

survey points offset so as to form a series of triangles across the width of the glacier. 

Multiple surveys of this profile will be performed (Levels 1 and 2), allowing the 

computation of strain rates. Results will be compared to strain rates from previous 

years in order to discern possible changes in the flow regime of the main trunk of the 

Taku Glacier (Level 2).

Timeline and Logistics: GPS surveys will commence during the last half of the Camp 17 

occupation and will continue for the following six weeks. During this time, the survey team 

will be in the field every day, spending 6 to 8 hours performing GPS surveys. Surveys on the 

Lemon Creek Glacier are conducted via ski. Due to the large geographic extent of the profiles 

on the Taku Glacier system, those surveys will be done via snowmobile. Faculty experts will 

supervise the field work, with students operating the GPS system and recording data. Data 

will be processed in camp, with basic results being used for the student project presentations 

in Atlin and Juneau at the end of the field season. In-depth data processing and presentation 

(Level 2) will take place as part of the student’s group project report, due near the end of the 

fall semester.

References (numbered by priority, i.e. study #1 first, #10 last):

1. Annual JIRP GPS Survey Reports, Crevassezone.org, http://crevassezone.org/reports-GPS.htm

2. JIRP Survey Overview, Crevassezone.org, http://crevassezone.org/tutorials/JIRP-Survey-
Overview.pdf and http://crevassezone.org/tutorials/JIRP-Survey-Overview.pptx

3. Calculating Glacier Movement Vectors, Crevassezone.org, 

http://crevassezone.org/tutorials/Glacier-Movement-Vectors.pdf

4. Basics of the Global Positioning System, Trimble, Inc., http://www.trimble.com/gps_tutorial/

5. Global Positioning System, Wikipedia.org, http://en.wikipedia.org/wiki/Global_Positioning_System

6. Application of GPS in Glaciology, by Matt King, Encyclopedia of Snow, Ice, and Glaciers (V.P. 

Singh, P. Singh, U.K. Haritashya, editors). http://crevassezone.org/tutorials/Application-of-GPS-
in-Glaciology.pdf

7. Glacier Monitoring Techniques, Ronald D. Karpilo, Jr., Department of Geosciences, Colorado 

State University, http://www.nature.nps.gov/geology/monitoring/files/geomon-06.pdf

8. Response of Glacier Basal Motion to Transient Water Storage, by Timothy Bartholomaus, 

Robert Anderson, Suzanne Anderson. Nature Geoscience, Vol. 1, Jan. 2008. 

http://www.nature.com/ngeo/journal/v1/n1/full/ngeo.2007.52.html and 

http://crevassezone.org/tutorials/Glacier-Basal-Motion.pdf

9. Direct Observations of Evolving Subglacial Drainage Beneath the Greenland Ice Sheet, by 

Lauren C. Andrews, Ginny A. Catania, Matthew J. Hoffman, Jason D. Gulley, Martin P. Lüthi, Claudia 

Ryser, Robert L. Hawley & Thomas A. Neumann. Nature 514, 80–83 (October 2, 2014).

http://www.nature.com/nature/journal/v514/n7520/full/nature13796.html

10. The Terrestrial Reference Frame and the Dynamic Earth, EOS, Vol. 82, No. 25, June 19, 2001, 

pp. 273-284. http://crevassezone.org/tutorials/ITRF.pdf

Student Project: Radio-Glaciology Measurements of the Juneau Icefield

2015 JIRP Student Project: Radio-Glaciology measurements of the Juneau Icefield

Faculty experts: Seth Campbell, Shad O’Neel

Overview: Each year, annual “point” measurements of mass gain (accumulation of snow) and mass loss (ablation) are collected across the Juneau Icefield (JIF) to assess whether it is gaining or losing mass (a concept known as mass balance).  These measurements are added to a 50+ year continuous record of mass balance on the Juneau Icefield.  The primary goal of the radio-glaciology project is to incorporate geophysical measurements from ground-penetrating radar (GPR) into determining spatial variability of glacier snow, firn, and ice as they relate to mass balance of the JIF.  We will use GPR to complete several objectives to include:

1.      Spatially extrapolating point measurement of winter accumulation across the JIF.

2.      Comparing winter accumulation determined from GPR data collected in 2012 with winter accumulation determined from GPR data collected in 2015.

3.      Assessing dimension changes in firn layers buried below the winter accumulation by comparing GPR profiles collected in 2015 and 2012.

4.      Assessing temporal changes in water content within the snow, firn, and ice  

Level 1 students are not expected to continue their work beyond the summer field camp unless computations and write up are not completed during summer. Level 2 students should expect to continue to work on data analysis beyond the summer season, with a more detailed analysis and report turned in near the end of fall semester.

A.      Snow accumulation. Snowpits will be excavated at several (15-25) established locations on Taku and Lemon Creek glaciers to the depth of the previous summer surface. In each pit a density profile will be computed and plotted as part of the annual mass balance program. The pits will be used as depth ground-truth for GPR profiles which are collected via snowmobile and/or ski on 5-50 km long transects across the icefield.  The GPR profiles will be used to extrapolate point measurement snow pit winter mass balance information across the ice field. (Level 1&2).  Level 1 students will provide accumulation thickness estimates from GPR and snow pit ground truth information. And qualitatively compare those measurements with similar data collected in 2012.  Level 2 students will convert winter accumulation thicknesses to snow water equivalence while estimating uncertainties in SWE measurements from instrument errors and from melt by using a supplied degree day model. 

B.      Firn evolution. Approximately 150 km of GPR profiles were collected across Taku Glacier in 2012 and show multiple layers of firn below the winter accumulation.  Here we propose to repeat collection of 2012 profiles in 2015 to compare firn layer dimensions and estimate changes relative to time (Level 1&2).  Level 1 students will qualitatively infer dimensions changes of firn layers using minimal ground-truth.  Level 2 students will attempt to quantitatively infer changes and incorporate multi-year snow pits (digging into and providing ground-truth at least into last year’s firn) into the study. 

C.      Snow Melt Study.  Snow accumulated on a glacier surface in the winter experiences significant melt through the summer season in temperate glacier environments.  As the surface snow melts, water percolates into deeper layers.  We are interested in determining how much melt occurs and where the melt travels to over the time because water content and snow density both play significant roles in the calculation of snow water equivalence in a snowpack using GPR.  Questions remain regarding how much melt stays within the winter snow pack after surface melt occurs and how much melt percolates into deeper firn and ice layers.  Here we will use advanced geophysical techniques such as migration, common midpoint (CMP) and Wide angle refraction and reflection (WARR) surveys to estimate changes in water content relative to time.  Available meteorological and snowpit data will be incorporated into this study to estimate meteorological impacts on melt and compare radar derived estimates of water content with field observations.  (Level 2).

Timeline and logistics: These studies can be completed in conjunction with snowpit excavations during the mass balance studies (with 2-3 days/week spent in the field).  The radar teams will use either snowmobile or skis to tow the radar systems for A&B.  Study C will be performed at one easily accessible location near Camp 10 through the course of the program.  For longer GPR transects, project members will travel to places where most students will not. Students should expect at least 1-2 days per week in camp processing data. New data will be collected, processed and preliminary interpretations made. Additionally, student reports will use other supplied data sets such as prior GPR profiles, meteorological, and snow pit data.  Several software programs will be used for analyses including radar processing, GIS (e.g. ArcGIS), and programming software (e.g. MATLAB). 

References (numbered by priority, i.e. study #1 first, #10 last):

(1)   Woodward J and Burke MJ (2007) Applications of Ground-Penetrating Radar to Glacial and Frozen Materials. J. Environ. Engineering Geophys., 1(12), 69–85

(2)   Bingham RG and Siegert MJ (2007) Radio-Echo Sounding Over Polar Ice Masses. J. Environmental and Engineering Geophysics, 1(12), 47–62

(3)   Spikes VB, Hamilton GS, Arcone SA, Kaspari S, Mayewski, PA (2004) Variability in accumulation rates from GPR profiling on the West Antarctic plateau. Ann. Glaciol., 39(1), 238-244

(4)   Kohler J, Moore J, Kennett M, Engeset R and Elvehoy H (1997) Using ground-penetrating radar to image previous years’ summer surfaces for mass-balance measurements. Ann. Glaciol.,  24, 355-360.

(5)   Arcone SA (2002) Airborne-radar stratigraphy and electrical structure of temperate firn: Bagley Ice Field, Alaska, U.S.A. J. Glaciol., 48(161), 317-334

(6)   Arcone SA and Yankielun NE (2000) 1.4 GHz radar penetration and evidence of drainage structures in temperate ice: Black Rapids Glacier, Alaska, U.S.A. J. Glaciol. 46(154), 477-490

(7)   Bradford JH, Harper JT, Brown J (2009) Complex dielectric permittivity measurements from ground-penetrating radar data to estimate snow liquid water content in the pendular regime. Water Resources Research. 45(8), 12 p 

Student Project: Icefield Reflectance and Albedo

2015 JIRP Student Project: Icefield Reflectance and Albedo

Faculty Experts: Allen Pope

Overview: Surface reflectance (sometimes called albedo, although if you choose this project you will learn why that isn’t strictly accurate) is an important property for understanding how much melt energy a glacier is absorbing. The Icefield reflectance project will use a field spectroradiometer to measure the spectral reflectance of glacier surfaces, studying the spatial and temporal variability of glacier spectral reflectance and albedo. Students will develop questions relating to processes that influence surface reflectance and design data collection strategies accordingly. Some suggestions are given below. The goal of this project is a better understanding of temporal and spatial variability in Icefield reflectance.

Level 1 students are not expected to continue their work beyond the summer field camp unless computations and write up are not completed during summer.

Level 2 students should expect to continue to work on data analysis beyond the summer season, with a more detailed analysis and report turned in near the end of fall semester.

Project breakdown:

Spectral reflectance: This is the basic unit of all subsequent projects. Radiance and irradiance measurements will be collected and students will process these data into reflectance spectra. Students will choose a range of locations and times to understand the spatial and temporal variability in glacier surface reflectance. Levels 1 & 2

Albedo: The next step beyond reflectance spectra, students will incorporate spectral reflectance and irradiance measurements to calculate glacier surface albedo. Students will investigate temporal and spatial variability in albedo resulting from changing illumination conditions and surface properties. Levels 1 & 2

Grain size studies: Students will study temporal and spatial variability in snow grain size by comparing direct observations using a snow card with calculations based on measured reflectance spectra. Level 2 {Possibly level 1}

Impurities: Students will investigate the impact that impurities (dirt/dust/soot) have on spectral reflectance (and albedo). Students can design controlled experiments or locate appropriate natural study sites. Levels 1 & 2

Compare with remote sensing: Understand how your point data scale up to reflectance measurements from airborne and satellite remote sensing measurements. Level 1 students will learn how to directly compare with satellite imagery. Level 2 students will have the opportunity to compare with 2015 observations and design a larger experiment.

Link with energy balance: Join forces with the energy balance modeling project to understand what your albedo measurements mean for surface mass balance. Level 2

Advisor’s Note: I focus on glacial remote sensing, so I focus on pointing the field spectroradiometer at snow and ice. If you’re interested in looking at other reflectance spectra (rocks, algae, or something else), that is something I’m open to, too!

Timeline and Logistics: There are two main constraints on this project: availability of the field spectroradiometer and appropriate weather for data collection. The field spectroradiometer should be available for at least two weeks in mid July, and possibly in early/late July (depending on shipping constraints), but there is nothing we can do about the weather except hope it is good! The field spectroradiometer and controlling laptop need to be charged every night, so fieldwork will be based out of camps, but travel with skis and possibly snowmobiles will be incorporated as the science necessitates it. Locations and frequency of data collection will be determined by student interest. Preliminary analysis will be conducted in camp. Further data collections will then be planned.

References (in approximate order of priority):

1. McArthur, A., 2007. “ASD Collection and Processing Guides,” NERC Field Spectroscopy Facility.

2. Skiles, M., 2015. Snow Optics Lab Protocols.

3. Hendriks, J, and P. Pellikka. “Estimation of Surface Reflectances from Hintereisferner: Spectrometer Measurements and Satellite-Derived Reflectances.” Zeitschrift Für Gletscherkunde Und Glazialgeologie 38, no. 2 (2004): 139–54.

4. Pope, A., and W. G. Rees. “Using in Situ Spectra to Explore Landsat Classification of Glacier Surfaces.” Journal of Applied Earth Observation and Geoinformation 27A (2014): 42–52. doi:10.1016/j.jag.2013.08.007.

5. Gardner, A. S., and M. J. Sharp. “A Review of Snow and Ice Albedo and the Development of a New Physically Based Broadband Albedo Parameterization.” Journal of Geophysical Research-Earth Surface 115 (2010): F01009.

6. Schaepman-Strub, G., et al. “Reflectance Quantities in Optical Remote Sensing - Definitions and Case Studies.” Remote Sensing of Environment 103, no. 1 (2006): 27–42. doi:10.1016/j.rse.2006.03.002.

7. Takeuchi, N. “Temporal and Spatial Variations in Spectral Reflectance and Characteristics of Surface Dust on Gulkana Glacier, Alaska Range.” Journal of Glaciology 55, no. 192 (2009): 701–9.

8.  Greuell, W, C. H. Reijmer, and J. Oerlemans. “Narrowband-to-Broadband Albedo Conversion for Glacier Ice and Snow Based on Aircraft and near-Surface Measurements.” Remote Sensing of Environment 82 (2002): 48–63.

9. Nolin, A, W., and J. Dozier. “A Hyperspectral Method for Remotely Sensing the Grain Size of Snow.” Remote Sensing of Environment 74, no. 2 (2000): 207–16. doi:10.1016/S0034-4257(00)00111-5.

10. Dumont, M. et al. “Contribution of Light-Absorbing Impurities in Snow to Greenland/’s Darkening since 2009.” Nature Geoscience 7, no. 7 (2014): 509–12. doi:10.1038/ngeo2180.

11. Painter, T. H., and J. Dozier. “Measurements of the Hemispherical-Directional Reflectance of Snow at Fine Spectral and Angular Resolution.” Journal of Geophysical Research 109 (2004): 21 PP. doi:200410.1029/2003JD004458.

Student Project: Geobotany, Nunatak and Periglacial Ecology and Entomology

2015 JIRP Student Project: Geobotany, Nunatak and Periglacial Ecology and Entomology 

Faculty experts: Alan Fryday, Karen Dillman, Saewan Koh, David Hik, Sean Schoville, Polly Bass

Overview of Projects and Goals:

The ecological research of the Juneau Icefield Research Program is important on a global scale. The nunatak and periglacial habitats provide information on the impact of climate change on high latitude alpine habitats.  Work to date has indicated a 68% species increase since the time of first historical work in nunatak habitats of this region. 

Baseline observations allow for monitoring future changes. Threatened species, range extensions, and invasive species have been observed on the nunataks.  Study of the periglacial and nunatak habitats of the Alaska-Canada Boundary Range allow for insights into the future of this biome, which are not available from other indicators.

Research themes include habit change, species assemblages; interactions between plants, animals, insects, and substrates. Abiotic variables including aspect, dominant wind direction, slope, precipitation, and lithology, among other factors are considered. Successional processes will be investigated in conjunction with Quaternary geomorphology and landform development in the periglacial environment.  A model for species richness determinations, developed in previous research on the icefield nunataks will continue to be tested on previously uninvestigated nunataks. The data will be used to determine the validity of a hypothesis of nunatak biogeography as a corollary to the theory of island biogeography.  Students will learn basic plant (vascular and nonvascular) identification techniques, ecological field research methodologies, data analysis techniques, sampling and project design, and collection and processing procedures. Students will contribute to and participate in ongoing research. 

Specific Objectives and Possible Project Directions

A.      Carry out vegetation surveys and observations on many nunatak sites, with some sites of special interest; Observe for changes in abundance and species composition; Improve the representation of Southeast Alaska in the flora of the herbaria of UAF and UAA.

B.      Contribute to the data set to test the plant species richness per unit area model, revise and re-evaluate.

C.      Observe for and record the presence of Festuca genus grasses, with interest in the presence of Neotyphodium. Observe for the presence of foragers. Prepare collections for genetic work.

D.     Observe for, record and report the presence of species range extensions, invasive or exotic species, or fungi of interest, in particular, Taraxum sp. and Exobasidium karstenii.

E.      Consider and observe interspecies and species substrate relationships, including observations for Nebria and Bambina genus beetles; foragers, including birds, other insects, animals; and plants.

F.       Observe for the presence of Nebria sp. for studies on the dispersal of the species on the nunataks and within Northwestern North American mountain ranges. Collect Nebria, record detailed habitat observations, and prepare samples for genetic work.

G.     Re-evaluate sites investigated by Henry Imshaug, survey, observe, record, and collect lichens. Carry out lichen and bryophyte baseline studies.

H.     Assist with observation for and collection of Cryptogramma crispa, C. acrostichoides, and C. sitchensis for genetic work and study of the species dispersal since the LGM. Members of the fern genus Cryptogramma, are known by their common name as the ‘parsley ferns’. Prepare collections for genetic work.

I.        Download and re-deploy digital temperature data loggers at select sites. Analyze this data in association with other variables. Consider influence of growing season length and variations in growing season on the habitats.

Timeline and logistics:  Introductory information on methodology and identification will take place at the beginning of the summer and be reinforced and reviewed throughout the summer as we traverse the icefield. At least 2-3 days/week will be spent in the field.  The ecology team will transport themselves, in most cases, to locations of interests.  Students should expect at least 1 day per week in camp working on data analysis.  New data will be collected, processed and preliminary interpretations made.  Two or more overnight field trips may take place to sites such the Nugget Ridge area, Sunday Point  and Brassiere Hills, possibly the Hole in the Wall and Twin Glaciers/ Camp 4 area, Juncture Peak and Shoehorn Peak area, Ivy Ridge, the Blob and/or F-10.

Possible conferences:

The Alaska Botanical Forum (will most likely be held in Fairbanks or Ketchikan in fall of 2015).

The Northwest Scientific Association Spring 2016 Conference, The Alaska Forum on the Environment Spring 2016 in Anchorage, The AISWG-CNPM(AK Invasive Species Conference) Fall 2015.

References:

Bjelland, T. 2003. The Influence of Environmental Factors on the Spatial Distribution of Saxicolous Lichens in a Norwegian Coastal Community. Journal of Vegetation Science(14) 4 525-534.

Cannone, N., Sgorbati, S., Guglielmin, M. 2007. Unexpected Impacts of Climate Change on Alpine Vegetation. Frontiers in Ecology and the Environment, 5(7):360-364

Halloy, S. R. P., & Mark, A. F. 2003. Climate-change effects on alpine plant biodiversity: A New Zealand perspective on quantifying the threat. Arctic, Antarctic, and Alpine Research. 35(2): 248-254.

Harvey, J.E. and Smith, D.J. 2013.  Lichenometric dating of Little Ice Age Glacier activity in the Central British Columbia Coast Mountains, Canada.  Geografiska Annaler: Series A, Physical Geography 95, p. 1-14.

Kammer, P. M., Schöb, C., and Choler, P. 2007. Increasing species richness on mountain summits: Upward migration due to anthropogenic climate change or re-colonisation? Journal of Vegetation Science. 18: 301-306.

Keeling, C.D., Chin, J.F.S. & Whort, T.P. 1996. Increased activity of northern vegetation inferred from atmospheric CO2 measurements. Nature. 382: 11 July,  146-149.

Koh, S. and Hik, D.D. 2007.Herbivory mediates grass-endophytes relationships. Ecology, 88(11); 2752–2757.

Koh, S. and Hik, D.D. 2008.Herbivory mediates grass-endophytes relationships Reply. Ecology, 88(12);3545-3549.

Smith, V. R., Steenkamp, M., & Gremmen, N. J. M. 2001. Terrestrial habitats on sub-Antarctic Marion Island: Their vegetation, edaphic attributes, distribution and response to climate change. South African Journal of Botany. 67: 641-654.

Walther, G.R., Beiβer, S., & Conradin, A. 2005. Trends in the upward shift of alpine plants. Journal of Vegetation Science. 16: 541-548.

Walther, G.R, Post, E., Convey, P., Menzel, A., Parmesan, C., Beebee, T. J. C., Fromentin, J. M., Hoegh-Guldberg, O., & Bairlein, F. 2002. Ecological responses to recent climate change. Nature. 416: 389-395.

Scherrer, D. and Körner, C. 2011. Topographically controlled thermal-habitat differentiation buffers alpine plant diversity against climate warming. Journal of Biogeography 38, 406–416.

Student Project: Stable Water Isotopes

JIRP 2015 Student Project: Stable Water Isotopes to Examine Moisture Transport and Snowpack Evolution on the Juneau Icefield.

Project leader: J. Kavanaugh

This study will use measurements of the stable water isotopic ratios δ18O and δD (see Footnote #1) to examine several aspects of the Icefield’s hydrology and snowpack. These isotopic ratios are influenced by a range of important environmental parameters, including temperature, relative humidity, phase transitions, and transport path characteristics, and can thus be used to examine the movement of water through the hydrological cycle. The proposed research project will examine isotopic signatures of both freshly-fallen snow (to examine lateral and vertical gradients in isotopic values) and the upper several meters of the snow and firn pack. An additional potential project will track the change in isotopic content of one or several JIRP participants as they cross the icefield. Although not confirmed at this time, it is possible that a portion of the isotopic analyses will be performed on the icefield using a Los Gatos Water Isotope Analyzer, which can determine δ18O and δD values from samples. The remaining samples (and duplicates of some or all samples analyzed on the icefield) will be analyzed at the University of Alaska Anchorage.

Students participating in this project will read papers selected to demonstrate the use of water isotopic techniques to both cryospheric research in particular and Earth system science in general.  Students involved in this project will have the option to either complete their contributions at or near the end of the summer field expedition (“Level 1”) or to extend their involvement through the Fall semester (“Level 2”).

Research Topics:                                    

1. Examining changes in isotopic ratios along lateral and vertical gradients. As moisture is transported from its source region inland, its isotopic signature changes as the result of (a) Rayleigh distillation (whereby moisture becomes progressively more depleted in heavy isotopes as less and less of the original moisture remains) and (b) the temperature dependence of isotopic fractionation upon phase change (e.g., condensation from the vapor phase). Snow samples will be collected along both lateral (i.e., along moisture path) and vertical (i.e., elevational) transects in order to tease out horizontal and vertical isotopic gradients. Ideally, these transects will be sampled in as short a time period as practical, and at least twice: the first during or shortly after a fresh snowfall (if conditions are deemed safe to do so) to capture unmodified isotopic values and the second after the snowpack has been exposed to several freeze/thaw cycles and other aging effects that could modify the isotopic signature. (Level 1 and 2) Following completion of JIRP, Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) models will be used to determine the air mass trajectory for the sampled precipitation events to determine along-path distances and moisture source characteristics. (Level 2)

2. Examining isotopic variations within the snowpack. A 2014 student study of isotopic signatures in snowpits indicated that water contained in ice lenses was generally isotopically lighter (i.e., more depleted in heavy isotopes) than was water contained in the surrounding snow. This difference is of interest because it can be used to examine whether ice lenses form from rainfall events, from the refreezing of melted snow, or from a combination of these two mechanisms. Students in 2015 will examine the isotopic signature of ice lenses, and the snow immediately above and below them, in much greater detail than was done in 2014, in order to address this question.

Additional work will be performed to examine the evolution of isotopic signatures with aging of the snow and firn. First, one or more snow pits will be dug to reveal two years’ worth of accumulated snow and firn (i.e., one year’s greater accumulation than typical). Firn samples in the layer dating from 1-2 years (i.e., corresponding to the snow sampled during JIRP 2014) will be analyzed, and isotopic values will be compared to those obtained in 2014 to determine the magnitude of change. Second, snow and firn will be sampled from the exposed faces of several crevasses and analyzed to determine whether isotopic values vary significantly (due to atmospheric exposure and possible meltwater contamination) from those obtained from snow and firn samples in nearby snow pits. Ideally, the multi-year snow/firn pits will be dug in locations that (a) were sampled for isotopic analysis in 2014 and (b) are near crevasses suitable for study. (Levels 1 and 2)

Footnotes

1These so called “delta values” are measures of the ratio of “heavy” vs “light” water molecules (e.g. those with 18O vs 16O isotopes, respectively) in any sample compared to a global standard.

References

Dansgaard, Willi. "Stable isotopes in precipitation." Tellus 16.4 (1964): 436-468.

Merlivat, Liliane, and Jean Jouzel. "Global climatic interpretation of the deuterium‐oxygen 18 relationship for precipitation." Journal of Geophysical Research: Oceans (1978–2012) 84.C8 (1979): 5029-5033.

Jouzel, Jean, and Liliane Merlivat. "Deuterium and oxygen 18 in precipitation: modeling of the isotopic effects during snow formation." Journal of Geophysical Research: Atmospheres (1984–2012) 89.D7 (1984): 11749-11757.

Kavanaugh, J. L., and Kurt M. Cuffey. "Space and time variation of δ18O and δD in Antarctic precipitation revisited." Global Biogeochemical Cycles 17.1 (2003).

Dansgaard, Willi, et al. "A new Greenland deep ice core." Science 218.4579 (1982): 1273-1277.