Climate-controlled submarine landslides on the Antarctic continental margin

International Ocean Discovery Program (IODP) Expedition 374
Ross Sea Continental Ice Shelf, Antarctica
Funded by: Natural Environment Research Council (NERC)
Date: 2023
Principal Investigator: Dr Jenny Gales , Associate Professor in Hydrography and Ocean Exploration
Part of the International Ocean Discovery Program Expedition 374 (2018–2023), led by Professor Rob McKay, Director of the Antarctic Research Centre at Victoria University of Wellington, Laura De Santis, a researcher at the National Institute of Oceanography and Applied Geophysics.
 
Antarctica's continental margins pose a potential tsunami risk to the Southern Hemisphere that could be caused by submarine landslides. Dr Jenny Gales and the team looked at the major submarine landslides compiled along the eastern Ross Sea continental slope to understand the factors driving slope failure and provide evidence to assess future geohazards. They identified:
  • weak layers beneath three submarine landslides, consisting of interbedded Miocene-to-Pliocene-age diatom oozes and glaciomarine diamicts.
  • the lithological difference – coming from glacial-to-interglacial variations in biological productivity, ice proximity and ocean circulation – saw changes in sediment deposition causing preconditioned slope failure
  • recurrent Antarctic submarine landslides were likely triggered by seismicity associated with glacioisostatic readjustment.
Ongoing climate warming and ice retreat may increase regional glacioisostatic seismicity, triggering Antarctic submarine landslides.
Research vessel JOIDES Resolution surrounded by sea ice as it approaches Antarctica's eastern Ross Sea (Credit: Jenny Gales)

Underwater landslides in Antarctica

Little is known about the probability and potential of the impacts of tsunami waves that could originate from Antarctica because few submarine landslides are documented. A potential geohazard risk, they are particularly sensitive to climate change – warmer Antarctic temperatures, higher sea levels and larger ice sheets – as well as any potential risks from internet cable connections to Antarctica.
Operating on the Iselin Bank, located on the eastern Ross Sea continental shelf, and adjacent to Hillary Canyon in Antarctica, researchers analysed the submarine landslide pre-conditioning and triggering of the Antarctic continental margin, with a high-resolution multidisciplinary analysis integrating downhole-log data with lithologic, chronologic, and seismic data. Through this, multiple weak layers were identified beneath a large submarine landslide complex.
Chronological data indicated that long-term climatic shifts may have played a critical role in the formation of weak layers prone to failure.

The discovery of 'weak layers'

A large submarine landslide complex extends more than 100 kilometres along the Iselin Bank upper slope. It consists of multiple submarine landslide scarps (herein scarps) and headwalls over 100 metres high and is divided into northern and southern regions based on bathymetric data availability. The seafloor is relatively smooth between the scarps, revealing multiple exposed bedding planes.
The southern submarine landslide region has two exposed scarps and one buried scarp. Landward of these scarps, the data showed stratified, parallel amplitude seismic reflectors that can be traced from the shelf edge. The seismic data showed that the slope failed along three parallel and continuous bedding planes, identified as the topmost continuous reflection beneath each scarp – referred to as 'weak layers'.
A revised age model was created of the expedition site (IODP Site U1523), with core-seismic correlations showing that the two weak layers have a minimum age range similar to 2.82 million years and 3.07 million years.

Climate change and ice retreat

The data obtained from the eastern Ross Sea have implications for constraining submarine landslide pre-conditioning and triggering around Antarctica. Large-scale recurrent slope failures have occurred on the Iselin Bank since at least since the middle Miocene Epoch (23.03 to 5.333 million years ago) of the Neogene period, with weak layers identified beneath three submarine landslide scarps.
Researchers propose that global climate changes influenced weak layer formation on the Ross Sea shelf and slop by creating distinct lithological contrasts between the diatomaceous weak layers and overlying diamicts that preconditioned slopes to fail.
This study indicates the importance of climate in preconditioning slope failure and provides insight into geohazards associated with future warming and ice retreat.
Antarctica Jenny Gales
Read the full study: Jenny A. Gales, Robert M. McKay, Laura De Santis, Michele Rebesco, Jan Sverre Laberg, Amelia E Shevenell, David Harwood, R. Mark Leckie, Denise K. Kulhanek, Maxine King, Molly Patterson, Renata G. Lucchi, Sookwan Kim, Sunghan Kim, ustin Dodd, Julia Seidenstein, Catherine Prunella, Giulia M. Ferrante & IODP Expedition 374 Scientists: Climate-controlled submarine landslides on the Antarctic continental margin, https://www.nature.com/articles/s41467-023-38240-y