Demonstration that a Viable Ice Core Record can be Produced from Mårmaglaciären, Kebnekaise, Sweden
Demonstration that a Viable Ice Core Record can be Produced from Mårmaglaciären, Kebnekaise, Sweden
Jeffrey Auger and Bjorn Grigholm
Climate Change Institute, University of Maine
Project Summary
This report is to follow up on a scientific expedition to Mårmaglaciären in the Kebnekaise Range, Sweden (Fig. 1), April 2015. The aim of the project is to begin searching for viable ice coring locations in northern Sweden for reconstructing atmospheric conditions over northern Scandinavia. The expedition included Profs. Per Holmlund and Margareta Hansson (Stockholm University, Sweden), Jeff Auger and Bjorn Grigholm (University of Maine), and Lars-Erik Poidnakk (Mårmaglaciären guide). Ice core samples from 4 sites were collected in the field and then transported to the University of Heidelberg, Germany, for radiocarbon dating and the Climate Change Institute for Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS) analysis. Helene Hoffmann (PhD candidate) prepared carbon samples for 14C dating using the accelerator mass spectrometer mini radiocarbon dating system at the Klaus-Tschira Laboratory in Mannheim, Germany. Jeff Auger will be preparing the ice cores for LA-ICP-MS analysis in January 2016.
Expedition Notes
Using Kiruna, Sweden as basecamp, we flew by helicopter to access Mårmaglaciären (1365 – 1720 m asl) combined with a snowmobile on ground to transport a gasoline powered generator and other heavy gear. The expedition took place during one day due to weather conditions for helicopter and snowmobile use. There were four total drill sites (1540, 1490, 1430, 1390 m agl) and one snow pit (1390 m asl, sampled at 10-cm resolution) (Fig. 2). Snowpack from the previous winter was anomalously high compared to recent years, at a total of greater than 2.5 meters. A Kovacs 3 inch core diameter drill driven by a Milwaukee electric corded hand drill was employed for ice core recovery. A generator was provided by the snowmobile driver/guide and used to power the hand drill. The cores were placed into plastic tubes and packed into a styropreen foam cooler for transport to the Climate Change Institute. From each drill site, a 1-liter sample (~30 cm core) was removed and placed into a plastic cooler for transport to Heidelberg, Germany for radiocarbon dating.
Preliminary Results
Previous work by Holmlund (1998) revealed annual layering in a 27.5 m ice core retrieved from the southern cirque of Mårmaglaciären (Fig. 2). This study also counted ~400 annual layers on the surface of the ice tongue. The purpose of this trip was to retrieve 4 ice cores (~3 m in length each) transecting the southern half of the ice tongue fed by the southern cirque (Fig. 2). These locations were chosen due to the findings from Holmlund (1998) as well as a visual glacial deformation on the surface of the northern tongue. The ice cores are now stored in the Ultra Cold Clean Lab for state-of-the-art, sub-annual analysis using the LA-ICP-MS trace element analysis at 121 micrometer resolution in the W. M. Keck Laser Ice Facility. Analysis using the LA-ICP-MS will be conducted starting in January 2016.
To analyze H and O isotope ratios a longitudinal slice was cut (102.5 cm in total length) from runs 3 & 4 (1.15 and 1.7 m depths, respectively) of Site 2. The slice was then cut into 2-cm resolution sections, melted in bottles, and sent to Douglas Introne (Climate Change Institute) for isotope analysis. Preliminary results of ∂2H and ∂18O from the comparison between the snow pit (10-cm resolution) and the ice core section from Site 2 reveal that the isotope record is washed out at the near surface level. Further isotope analysis from each site (including Site 2 at depth) may still prove to show an isotope record.
Radiocarbon dating reveals the age of the top 33 cm section of run 2 (0.6 m depth) fromSite 1 to be ~1183 +/- 218 years before present. The bottom 38 cm section of run 4 (1.24 m depth) from Site 3 is found to be ~2602 +/- 544 years before present in age. The oldest age aligns with Dr. Per Holmlund’s hypothesis of about 2000 years. The ice sample from site 2 is still in line to be dated in Germany.
Conclusions
Holmlund (1998) concludes that there are at least 15 glaciers in Sweden (including Mårmaglaciären) that contain cold, well preserved ice reaching 80 – 120 m in depth. With further isotope analysis of deeper runs from Sites 1 & 2 (reaching depths of over 3 m) and LA-ICP-MS chemical analysis, we can show if Mårmaglaciären is a viable location for future drilling projects. The ages from Sites 1 & 3 have a difference of more than 1000 years suggesting that annual layering may exist between these sites. From the initial isotope analysis, the surface is most likely ablating showing the importance of analyzing Mårmaglaciären as well as other mountain glaciers in the Kebnekaise Range before they completely disappear.
Moving forward, a deeper core ( >10 m) from Mårmaglaciären would be needed at a higher elevation than that of Site 1 (1490 m agl) to analyze both isotopes and chemistry. A deeper bore hole can also show the 10-m depth temperature reading to estimate the annual average air temperature over Mårmaglaciären. Other drill sites in the Kebnekaise Range should be investigated to determine whether more mountain glaciers contain a preserved chemistry record to be used for reconstructing past atmospheric circulation over northern Scandinavia.
Acknowledgements
We would like to express our deep gratitude to the Dan and Betty Churchill Exploration Fund for the opportunity to be involved in this project. Thank you also to Drs. Paul Mayewski, Per Holmlund, Sharon Sneed, Roger Hooke and Andrei Kurbatov, and Douglas Introne for helping in the proposal writing and logistics; Lars-Erik Poidnakk (guide) and Kallax Flyg (helicopter company) for transportation; Dr. Pascal Bohleber and Helene Hoffmann for radiocarbon dating and logistics.
Citations
Holmlund P (1998). Glacier Mass Balance and Ice-Core Records from Northern Sweden. Ambio27 (4), 266-269.