Analyzing basin-scale sedimentary processes in Lake Midsommer to reconstruct Holocene glacial dynamics in northern Greenland

Project description

Motivation
Rapid Arctic warming has not only led to increased melt from the Greenland Ice Sheet, but also from glaciers and ice caps at the periphery of the ice sheet (Carrivick et al., 2023). Ice loss in these glacial systems has been particularly notable throughout northern sectors of Greenland (Carrivick et al., 2019; Khan et al., 2022). In order to contextualize recent ice retreat, longer term records of glacier dynamics are needed to constrain changes over a broader range of climate conditions. This project will focus on reconstructing changes in glacier input to Lake Nedre Midsommersø in the Wandel Dal valley of northern Greenland. The lake is located in the High Arctic of northern Greenland and receives runoff from the Greenland Ice Sheet and several small ice caps. Limited information is known about the ice history of this region since deglaciation of the valley c. 8 ka BP and this project will explore the characteristics and timing of sedimentary changes identified in sediment cores from the lake.

Nedre Midsommersø is a large, multi-basin lake with a surface area of 30-km2. Inferring past climate conditions from sediment records from large lacustrine systems can be challenging because of the greater number of influences on sedimentation as compared to smaller, single-basin systems. Sedimentation in Nedre Midsommersø is complicated by having multiple inlets that drain different sub-watersheds, a range of water column properties within basins of varying depths, and different biological vs. minerogenic inputs across a basin. In order to develop paleoclimate information from Lake Midsommersø sediment cores, high-resolution computed tomography (CT) scanning will be performed to rapidly characterize sediments, fingerprint depositional processes, and quantify sediment properties. This project will focus on the application of CT scanning to a suite of four sediment sequences recovered from the lake. The goal of the project will be to characterize basin-wide sedimentary changes driven by varying degrees of glacial inputs since deglaciation of the basin (c. 8 ka BP) and during the Neoglacial period (c. 3-4 ka BP). Interpretations will primarily be based on CT scanning data in conjunction with measurements of other physical properties. The project will contribute to developing paleoclimate information from Midsommersø and advance the application of CT scanning to the evaluation of sedimentation in large lacustrine systems.

Research Questions
How do changes in glacial inputs to Nedre Midsommersø relate to regional climate conditions during the Holocene?
What is the signature of glacially-derived sediment inferred from CT data?
How do basin-scale processes influence sedimentation throughout Nedre Midsommersø?

Work Plan & Methods 
Nedre Midsommer sediment cores will be CT scanned at the UiB EARTHLAB facility. Data will be processed to quantify sedimentary changes and characterize 3D morphometry of specific layers within lithologic units. Age-depth models will be developed based on radiocarbon dating, analysis of short-lived isotopes (210Pb, 137Cs), and analysis of paleosecular variations. Additional physical sedimentary data will be collected as needed and may include: grain size analysis, X-ray fluorescence (XRF) for geochemical fingerprinting, surface magnetic susceptibility, and bulk density.

Proposed course plan during the master's degree (60 ECTS):
GEOV217 / Geofarer (høst, 10 stp.)
GEOV222 / Paleoklimatologi (høst, 10 stp.)
GEOV336 / Lab- og metodekurs i kvartærgeologi (høst, 10 stp.)
GEOV225 / Feltkurs i kvartærgeologi og paleoklima (vår, 10 stp.)
GEOV302 / Dataanalyse i geovitenskap (vår, 10 stp.)

Prerequisites
The thesis must be written in English du to a supervisor from the US.

Field- lab and analysis
Three months of work on CT images.