Holocene History of Svalbard Ice Caps and Glaciers

The aim of this project was to conduct geological fieldwork on northeast Svalbard in order to collect lake sediment cores that might reveal the glacial and environmental history over the last c. 10,000 years of this part of the Arctic. An international field expedition to northeast Svalbard, supported by the Carlsberg Foundation, was undertaken in July-August 2015. We successfully obtained sediment cores from three threshold lakes. The preliminary results reveal that the sediment cores contain a palaeo-environmental record back to the last deglaciation. Some of the sediment cores contain marine sediments in the base and, hence, reveal when the area was isostatically uplifted above sea level. The upper part of a core from the island Nordaustlandet shows a sequence of mid-Holocene organic sediments overlain by glacial meltwater clay. The glacial meltwater clay was deposited during a major glacier advance during the Little Ice Age, culminating in c. 1850. At this site, the Little Ice Age appears to be the most advanced Holocene glacier position. This project and similar efforts elsewhere in the Arctic aim to obtain a spatial and temporal overview of past glacier, climate, and sea level fluctuations. Understanding these natural variations is a prerequisite for providing robust models of future development and, hence, of broad societal interest.

Introduction

Lake sediments can be used to develop high resolution climate and glacier reconstructions, which are valuable in predicting antecedent changes in the natural environment. Sediment archives are especially useful in high-Arctic Svalbard where glaciers can respond rapidly to relatively minor shifts in temperature and precipitation, resulting in potential detailed records of regional climate fluctuations at multidecadal/centennial resolution, as well as insight into Holocene sea level. Our project aims to advance knowledge of glacier front fluctuations, sea level variability and their governing factors by acquiring lake sediment cores adjacent to major ice caps in an understudied part of the Arctic: NE Svalbard. We analyse these lake sediment archives, compare with data from previous western Spitsbergen studies, and attempt to identify whether glacier fluctuations are driven by regional climate variations, internal glacier dynamics (surge activity), or some combination of the two. We expect that lake sediments from NE Svalbard will provide unprecedented detail of past glacier and climate conditions and will contribute to a more holistic understanding of the Holocene history of Svalbard, thus bettering our understanding of processes, dynamics, and controls that drive shifts in climate throughout the North Atlantic.

“The lake sediment cores from northeastern Svalbard can be used to develop high-resolution climate and glacier reconstructions back to the last ice age.”

Holocene Studies Where the North Atlantic Meets the High Arctic

The Holocene climate has fluctuated between warmer and cooler periods as well as relatively humid and dry conditions on decadal to centennial timescales. The onset, duration and driving factors related to these changes are not well understood but are considered to be amplified in polar regions where minor shifts in temperature and precipitation have major impact. Not only is high-Arctic Svalbard (74-81°N) sensitive to slight shifts in climate, but the archipelago is located along the dominant corridor of atmospheric moisture between the Atlantic and the Arctic Basin (Fig. 1). The islands are positioned at the northern extent of the Gulf Stream (North Atlantic Drift) and the southern border of the Arctic sea ice front. These factors combine to make the region an optimal site to study past climate and current processes as a means of better predicting antecedent climate. Svalbard’s unique location also allows for the potential preservation of climatic shifts and sea level fluctuations in both terrestrial and lacustrine sediment archives.

At present, knowledge of the spatial changes of glaciers and ice caps on Svalbard through the Holocene lacks key details. For example, the Little Ice Age (LIA) is the best documented glacial and climate event occurring during the Holocene, and yet spatial extent, onset, duration, and causal factors remain poorly understood. In numerous locations around Svalbard, glacial landforms and deposits that pre-date the LIA moraines exist, yet little is known about the spatial and temporal relations of these landforms. Not only are climatic shifts on Svalbard throughout the Holocene poorly constrained, but northeastern Svalbard (particularly Nordaustlandet and northeastern Spitsbergen) has not been studied in detail except during several campaigns during the 1950s (Blake, 1962). Modern studies that focus on reconstructing Holocene history from lacustrine and terrestrial archives have concentrated on proglacial lakes of small none-surging cirque glaciers located on the west coast of Spitsbergen (van der Bilt et al., 2015).

Figure 1. Overview map of northern Svalbard with the expedition route from Longyearbyen to key field sites (red stars) in NE Svalbard. Inset map displays the high-Arctic location of Svalbard.

Selection of Lakes for Sediment Coring

Lithostratigraphic logging

Detailed lithostratigraphic logging and subsampling of terrestrial macrofossils and mollusk shells is used to identify shifts in depositional environments. Subsamples are radiocarbon dated (AMS ¹⁴C) to provide chronological control of the sediments and date major geological events (Fig. 3).

Unstudied lakes were targeted in NE Spitsbergen based on size, distance from the coast, elevation above sea level, and glacial meltwater influence. Lakes located at elevations below the Holocene marine limit will have a distinct shift in sedimentation and fauna at the transition between fjord and lacustrine environments. Dating the transitional sediments deposited during the isolation of these lake basins can provide valuable insight to the regional sea level history and uplift rates. Lakes that currently or previously received meltwater from glaciers were also selected because sediment archives preserved in these threshold lakes potentially can provide insight to glacier activity at an annual resolution. The basic concept of a threshold lake is the basin only captures glacial meltwater when glaciers are very advanced (Briner et al., 2010). Under ‘normal’ conditions, such lakes experience only organic sedimentation. During periods with advanced outlet glaciers (by surge or climate), glacial meltwater drains into threshold lakes that are otherwise only fed by surface runoff. Outside the limestone bedrock regions of Svalbard, the organic sediments are ideal for radiocarbon dating, and the lake sediments therefore offer an excellent archive and chronology of glacier advances. The selected lakes could potentially contain marine-basin isolation histories and sediments of glacial input dating as far back as the last deglaciation (Fig. 2).

Fieldwork in Northeast Svalbard

During a short time window in the summer season (end of July to mid-August), NE Svalbard can been accessed by boat, taking roughly 1.5 days from Longyearbyen depending on sea ice and weather conditions (Fig. 1). Following a zodiac transport from the main vessel to the coast, field equipment including sediment corers, bathymetry instruments and a small portable zodiac are carried to the study lakes. Prior to the lake coring, detailed basin bathymetry is recorded and a survey of the local catchment is conducted. Bathymetry and the site overview are important to locate the deepest basin in the lake and identify potential inflows and sources of sediment in the catchment, respectively. The coring itself is performed using lightweight piston-corers that enable us to take overlapping 2.8 m long sediment cores at water depths up to 50 m. At least one short gravity core (ca. 0.75 m) with undisturbed mud-water interfaces was also collected from each lake. The coring was conducted out of a small inflatable non-motorised raft (Fig. 2). A research expedition grant from the Carlsberg Foundation facilitated logistics and acquisition of these lake sediment cores.

“The research expedition grant from the Carlsberg Foundation made it possible to travel to this remote part of the Arctic to collect unique lake sediment cores.”

Figure 2. Coring proglacial lake Kløverbladvatna on Oxfordhalvøya, Nordaustlandet. View to the east with Etonbreen (Austfonna’s western outlet) in the background. Holocene beach ridges indicate the lake basin could contain marine sediments. White circle marks coring zodiac.

Preliminary Results

ITRAX

The ITRAX core scanner at The Natural History Museum of Denmark provides high-resolution photographs, magnetic susceptibility, and X-ray fluorescence analysis of the sediment cores. Scans of our half-cores highlight the sedimentology and stratigraphy and provide a basis for further analyses.

More than 10 metres of lake sediments from NE Svalbard were extracted from three proglacial threshold lakes, located both above and below the upper marine limit. Samples were shipped, split open, logged, and analysed in the sediment lab and ITRAX core scan facility at the Natural History Museum, University of Copenhagen. A selection of macrofossils of terrestrial plants was sent to be radiocarbon dated at the Ångström Laboratory at Uppsala University, Sweden (Fig. 3). Dates from the initial sample batch are stratigraphically ordered and fit with our general interpretation (Fig. 3). Stratigraphy and dates from the upper section of the Kløverbladvatna core suggest that over the last 3,000 years, Etonbreen was most extended during the Little Ice Age, and peaking in the 1850s. This might indicate that the LIA was the climax of Neoglacial cooling for Etonbreen. More macrofossils from the Kløverbladvatna core will be submitted to ¹⁴C dating in order to develop a robust chronology.

“We are excited to see that some lakes also contain marine-basin isolation histories and add to our knowledge about the isostatic uplift and sea level history during the last 10.000 years.”

Figure 3. Composite sediment core from Kløverbladvatna. Enlarged sections highlight boundaries between depositional environments. Initial ¹⁴C ages from the upper core are calibrated. Ice rafted debris and in situ Nuculana pernula mollusk suggests a marine depositional environment for the lower part of the core.

Further Use of the Project’s Results

Results from the August 2015 field campaign will be compiled into three to four peer-reviewed, scientific articles and will be a part of Wesley Farnsworth’s PhD project. Findings will also be presented at international conferences. These studies are valuable for the scientific community and researchers using palaeo-climate records and processes to model future environmental conditions. Understanding past climate and sea level change is a key issue of high societal relevance, considering the expected future changes, particularly in the Arctic. Additionally findings from the August 2015 campaign will form the groundwork for our understanding of the holistic Holocene history of Svalbard (not just the west coast of Spitsbergen). These results will be used in research-based teaching at both the Natural History Museum of Denmark and The University Centre in Svalbard.

References

Blake, W. 1962. Geomorphology and glacial geology of Nordaustlandet, Spitsbergen. PhD thesis, Ohio State University, Columbus, OH.

Briner, J.P., Stewart, H.A.M., Young, N.E., Phillips, W., Losee, S. 2010. Using proglacial threshold lakes to constrain fluctuations of the Jakobshavn Isbræ ice margin, western Greenland, during the Holocene. Quaternary Science Reviews 29, 3861-3874.

Authors

Wesley R. Farnsworth^1,2, Anders Schomacker^2,3*, and Ólafur Ingólfsson^1,4

¹The University Centre in Svalbard (UNIS), P.O. Box 156, N-9171, Longyearbyen, Norway

²Department of Geology, UiT The Arctic University of Norway, Postboks 6050 Langnes, N-9037 Tromsø, Norway

³Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K., Denmark

⁴Institute of Earth Sciences, University of Iceland, Askja, Sturlugata 7, IS-101 Reykjavík, Iceland

*Corresponding author. E-mail: anders.schomacker@snm.ku.dk