Improving constraints on the hydroclimate variability of northern Greenland

Project description

Motivation
The rapid warming of the Arctic in recent decades has been accompanied by significant changes in the regional hydrologic cycle. Hydroclimate changes are manifested in shifting seasonality of precipitation, more precipitation falling as rain rather than snow, and greater frequency of heavy rainfall events. The magnitude and characteristics of change vary across the Arctic, but collectively, have substantial implications for landscapes, ecosystems, human-environment interactions, as well as infrastructure. Despite these ramifications, future evolution of the Artic hydrological cycle remains poorly understood. In order to improve understanding of Arctic hydroclimate, longer term perspectives are needed that characterize a range of climatic regimes and that can be used to test future climate model scenarios.

The goal of this project is to improve constraints on hydroclimate variability of northern Greenland over the last c. 8000 years by analyzing lake sediment cores from Lake Midsommer in the Wandel Dal valley. Nearby weather station data indicate a rise in mean annual air temperatures of c. 0.6°C/decade and a two-fold increase in total precipitation since the 1960s, demonstrating the sensitivity of this area to climate change and justifying the need for longer term records. Detailed sediment characteristics will be used to interpret the nature and timing of changes in runoff to the lake driven by snowmelt and rainfall, which have likely varied significantly since deglaciation of the valley c. 8000 cal yr BP. In addition, the Wandel Dal valley was an important location for some of the earliest human settlements in Greenland and contains archaeological evidence for several phases of settlement and abandonment over the last 4500 years. Paleoclimate records developed as part of this project will also provide climate context for prehistoric human colonization of the region.

Research Questions
How do the frequency and magnitude of runoff/flood events vary throughout the Holocene?
Can the timing of runoff/flood events in northern Greenland be correlated to regional climate system dynamics?
How do they past variations in runoff/flood events compare with historic or projected future hydroclimate conditions?

Work Plan & Methods
This project will involve the analysis of sediment cores from Nedre Midsommersø to develop chronologic control and generate a detailed assessment of physical sediment characteristics. Age-depth models will be developed based on radiocarbon dating, analysis of short-lived isotopes (210Pb, 137Cs), and analysis of paleosecular variations. A multi-proxy approach will be applied to characterize the depositional signatures of sediment inputs to the basin. Analyses will include: X-ray fluorescence (XRF) for geochemical fingerprinting, surface magnetic susceptibility for core correlation and quantification of inorganic sediments, grain size analysis to quantify sorting and potential event layers, and 3D morphometry based on CT scans. Data will be analyzed using statistical approaches to quantify the dominant trends and shared variability, and will be compared to other time series records from throughout the region to interpret paleoclimate connections.

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
Master theis must be written in English due to co-supervisor from US.

Felt- lab- og analysearbeid
Three months with laboratory work.