Using lake sediments to constrain the timing and timing of Greenlandic tsunamis

Project description

As glaciers rapidly retreat in the facing of on-going and accelerating climate warming, they leave steep slopes in their wake that are no longer protected (buttressed) by ice. Instability is further promoted by permafrost melt, and an increase in run-off. As demonstrated along glacierized margins around the world, such slopes are prone to landslides. When plunging into a fjord, these events might trigger destructive tsunamis too. This risk is particularly great in Greenland, owing to the scale of the landscape – the largest fjords and glaciers found in the northern hemisphere, as well as the rapid pace of glacier retreat. Indeed, in 2023, a tsunamigenic landslide on the island`s east coast triggered a 200-meter-high wave and a 9-day-long seismic event. Despite the risks they pose, our understanding of the frequency and magnitude of such events is near non-existent. The analysis of sediments from lakes perched above fjords can help us fill this knowledge gap. When sufficiently sheltered, rising wave water may pond in these sites, and allow deposition of suspended sediment. If preserved during subsequent discharge peaks, such so-called slackwater deposits can record the timing and frequency of tsunami floods over thousands of years, while their elevation constrains flood magnitude. This project harnesses the potential of this conceptual framework by targeting slackwater sediments from a strategically located lake in Scoresby Sund in Eastern Greenland. As the world`s largest fjord, abutted by steep slopes with widespread evidence of slope instability, and shaped by rapid glacier retreat, this area is highly promising to look for the traces of past tsunamis. You will analyze material from informally named Screaming Bird Lake, which is perched high above the modern fjord and only flooded during extreme events. You will identify these using a combination of physical properties (density and organic content), grain size, Computed Tomography (CT) and elemental geochemistry (XRF). In addition to these methods, available hydraulic simulations and UAV-derived Digital Elevation Models are available to estimate the magnitude of past floods that inundated the lake. The main goal of this project is to assess whether exceptionally large tsunamis deposited sediments in our study site since the area re-appeared from the melting ice around 10 000 years ago, determine their volume, and assess whether these events occurred during phases of rapid climate change (like today), by dating them using radiocarbon samples. Finally, analysis of the structure of tsunami deposits will unravel the sequence of such events: modern observations reveal that fjord environments are not just struck by one landslide-triggered wave, but by standing waves, as water
sloshes back and forth. Upon completion, this project will deepen our understanding of the relations between fjord tsunamis, climate change, and risk hazard. We therefore envision opportunities for publication, also as planned work is carried out as part of the on-going GLAVE project that is funded by the Polish National Science Center (NCN), which offers exciting opportunities for collaboration (including short stays and conference visits) too.

Proposed course plan during the master's degree (60 ECTS)

GEOV217 - Geohazards (10 ECTS)
GEOV222 - Paleoclimatology (10 ECTS)
GEOV336 - Field and Laboratory Course in Quarternary Geology (10 ECTS)
GEOV225 - Field Course in Quarternary Geology and Palaeoclimate (10 ECTS)
GEOV302 - Data analysis in earth science (10 ECTS)
GEOV331 - Palaeoceanography (5 ECTS)
GEOV300 - Selected topics in Geoscience (5 ECTS)

Felt- lab- og analysearbeid / Field-, lab- and analysis work

You will spend quite a bit of time working in the EARTHLAB sediment lab facility of the department, analyzing the sediments using a range of physical and scanning methods that include X-ray fluorescence (XRF), Computed Tomography (CT), as well as grain size analyses. Additional methods might include remote sensing (the investigation of satellite time series, or photogrammetry models). The sediments are available here in Bergen: we know they contain at least one tsunami deposit.