The objective of the project was the investigation of englacial melt water channels of Svalbard glaciers in order to find in situ organic material within glacier caves. Specified organic material found beneath glaciers was meant for radiocarbon dating and creation of reliable geochronologies of glacier recessions with considerable smaller glacier termini than present on Svalbard. First radiocarbon dating results ever from organic material found under a glacier’s bottom of glacier Longyearbreen will be published this year. The different moss species ranging from Tomentypnum nitens, Sanionia uncinata, Distichium spp., Syntrichia ruralis gave ages between 1900 and 1100 cal yr BP (Humlum et al., 2004).
Work performed and results During the fieldwork in April 2004 I took all effort to find more datable material under several glaciers on Svalbard. I was looking systematically for organic material within glacier caves formed by englacial melt water streams. Several glacier caves were explored by means of alpine techniques and measured. UNIS provided help in logistics for the Arctic Fieldwork. However, I was aware that finding datable material in Svalbard could just be the start of a lifetime project, which can by no means be finished within a two-years-postdoc project. Five days of fieldwork were used in order to find the entrances of the marked caves on Tellbreen, Fangenbreen, Blekumbreen, Mälarbreen, Austre Brøggerbreen. The entrances were deeply covered with snow (up to 5 m) and it took several hours to clear the entrances from snow. Three days of fieldwork on Bünsowland in order to investigate Murdochbreen and Methuenbreen could not be used because of a snowstorm. Tillbergfonna glacier cave was explored during two days and the englacial melt water channel does not reach the bottom. Close to the glacier front, the englacial water channel develops to a supraglacial channel and is filled with snow and frozen melt water (Figure 1). Tellbreen, Boltonbreen, Fangenbreen and Mälarbreen glacier cave were each explored during one day and the channels are also filled with snow and frozen melt water in several decameters distance from the entrance. Longyearbreen glacier cave was measured with a Leica distometer, a compass and an inclinometer during three days (Figure 2). This work was performed in order to investigate changes of the channel geometry since the last measurements in 2002. Indeed the channel geometry has changed quiet enormously since 2003. The vegetation found in one glacier cave in 2001 and still accessible in 2003 was not accessible anymore. Murdochbreen glacier cave was explored during one day. This melt water channel path is very interesting, because the supraglacial channel geometry develops directly into a subglacial channel without succession via an englacial geometry. Unfortunately, no datable vegetation remains could be found beneath this glacier, the channel was completely filled with melt water sediments (Figure 3). The same situation was found in the side melt water channel of Austre Brøggerbreen. The main entrance in the middle of Austre Brøggerbreen was already filled with melt water in end of April after the unusual warm period in April (about 5˚C higher temperatures than mean April temperatures) (Figure 4). The investigation of Pedersenbreen glacier cave also resulted in that the englacial channel developed into a supraglacial channel. The most spectacular glacier cave was found in Methuenbreen. It was investigated during four days of fieldwork by means of measuring and documenting by photographs. This cave reaches the bottom of the glacier beneath ca. 60 m of the glacier’s surface and has a diameter of 23 m at the bottom (Figure 5). The glacier ice at the bottom is eroded about 1-2 m by circulating water during the melt water period. The bottom was visible below 1.5-2 m frozen melt water and consists of bare rocks without any vegetation. The strength of water in this moulin eroded any possible remains of vegetation at the bottom of Methuenbreen. Conclusions No datable material except under Longyearbreen could be found due to the following reasons: 1) Several englacial and supraglacial channels of the glaciers do not reach the bottom of the glaciers. 2) In Methuenbreen melt water eroded all possible vegetation at the bottom of the 60 m deep Moulin. 3) In Austre Brøggerbreen and Murdochbreen the active melt water channels were completely filled with sediments and no in situ vegetation was visible. 4) The subglacial channel below Longyearbreen is in an inactive state. In the years 2001-2003 the channel was accessible, whereas in spring 2004 the channel was not accessible anymore and another channel has become the main active channel. Therefore, it is a random situation that the vegetation has been found and it needs the systematic effort of several years to find vegetation under other glaciers in such a remote area.
UNIS AWIPEV base Tellbreen, Fangenbreen, Mälarbreen, Austre Brøggerbreen, Murdochbreen, Methuenbreen, Tillbergfonna, Boltonbreen, Longyearbreen, Pedersenbreen
UNIS AWIPEV
Publication: Humlum, O., Elberling, B., Hormes, A., Fjordheim, K., Hansen, O.H., and Heinemeier, J. (2005): Late-Holocene glacier growth on Svalbard, documented by subglacial relict vegetation and living soil microbes. The Holocene, 15,3, 396-407.