Glacier dynamics in the fjords of Svalbard, inferred from submarine landforms and marine sediment cores

Abstract

This thesis presents a reconstruction of the late Weichselian, deglacial and Holocene glacial history of the Svalbard fjords, focusing on eastern Svalbard. The study is based on high-resolution multibeam data, shallow acoustic (chirp) data, marine sediment cores, historical maps and aerial- satellite images. During the Last Glacial Maximum the Svalbard Barents Sea ice sheet reached the shelf edge around Svalbard and was drained by large ice streams along its western and northern margins, located in the same areas as the present day cross-shelf troughs. In northeastern Svalbard, fast- flowing ice converged into the Hinlopen Strait ice stream from the surrounding fjords. Submarine landforms indicate that ice flow velocities increased as ice flowed from the inner- to the outer fjords and the shelf. The deglaciation from the northeastern shelf edge proceeded rapidly by ice lift-off in the troughs and deeper parts of the fjords, whereas the shallower areas experienced slower retreat with minor re-advances. The inner fjords around Nordaustlandet were ice free prior to 11.3-10.5 ka BP years. During early- to mid-Holocene tidewater glaciers in Mohnbukta and Vaigattbogen experienced at least one surge-type advance. These pre-Little Ice Age surges differentiate the east coast glaciers from the west coast glaciers. The early Holocene advance in Mohnbukta has been attributed to rapid climatic and environmental change at the end of the deglaciation, leading to dynamic disequilibrium and an environmentally induced jump into surge-mode. This suggests a more dynamic Holocene glacial history in Svalbard than previously stated, also indicating that the role of climate is more important in the evolution of general surge patterns than previously presumed. Similarly, climatic and environmental changes at the end of the Little Ice Age could explain why many Svalbard glaciers, both on the west and east coasts surged in that time period. Today, the majority of Svalbard’s fjords accommodate tidewater glaciers, of which several have been recorded to surge. Commonly the glaciers have surged at least twice during the Holocene. The surging tidewater glacier landform assemblages share many similarities and can be used to identify past surges in the geological record. In this study the submarine morphology has been used to identify three new surge-type glaciers in Wahlenbergfjorden. The surge history of the Svalbard glaciers is diverse and even though the landform assemblages share many similarities, they all feature differences, suggesting that local conditions are important in the evolution of glacial surges.