Effect of climate change on greenhouse gas fluxes from marine Artic regions

Project Information

GreenFlux

Grant agreement ID: 101060851

DOI

10.3030/101060851

Project terminated on 15 May 2025

EC signature date 17 June 2022

Start date 1 March 2023

End date 31 May 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 230 774,40

Coordinated by

AARHUS UNIVERSITET
Denmark

Periodic Reporting for period 1 - GreenFlux (Effect of climate change on greenhouse gas fluxes from marine Artic regions)

Reporting period: 2023-03-01 to 2025-05-31

Summary of the context and overall objectives of the project

Which role do greenhouse gasses emitted from the sea floor play in climate change? GreenFlux is an original investigation into the contribution of high-latitude continental margins and shelf seas to global greenhouse gas emissions by assessing the sensitivity of sub-seafloor permafrost and gas hydrates to climate change. With innovative and integrated approaches, I evaluated how the environmental changes since the Last Glacial Maximum (LGM; about twenty thousand years ago) impacted gas release from the seafloor and which helps to assess how the Arctic may develop in a future warmer world.

Rising concentrations of greenhouse gases in the atmosphere since pre-industrial times cause the Arctic to warm at a faster pace compared to the planet. This is known as Artic amplification and causes an exacerbation of climatic effects such as the melting of the Greenland ice sheet. Particularly in the Arctic, key players that likely have a strong impact on global climate are permafrost soils and marine gas hydrates, because both host large amounts of carbon. Permafrost in marine sediments has likely developed in aerially exposed areas during the extreme cold (-20°C annual mean temperature) and low sea level (-120 m) of the Late Pleistocene. These conditions (high-pressure/low-temperature) were also favorable for gas hydrate formation. Thus, “relic” permafrost and gas hydrate may exist in the Arctic to present water depths of 120 m (Figure 1). Current global warming may cause an increase in melting of permafrost and gas hydrates and thus release more greenhouse gases into the ocean or even the atmosphere (climatic feedback). However, the sensitivity of permafrost and gas hydrates to rising temperatures is poorly constrained. Our understanding of the involved geologic processes in the Arctic predominantly relies on observations from natural cold seeps offshore Svalbard. In and around Northeast (NE) Greenland, these cold seeps have received very little attention and it thus remains a “white gap” on the map. This is partly because of a lack of data and insufficient mapping at high resolution, in particular for the NE Greenland shelf. Because NE Greenland is a white gap, current compilations may significantly mis-predict the carbon budget in the Arctic.

My project “Effect of climate change on greenhouse gas fluxes from marine Artic regions” (GreenFlux) aims to provide groundbreaking scientific basis on the underlying geologic processes of greenhouse gas emissions from marine sediments.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

To meet the project objectives, I applied integrated, interdisciplinary approaches combining paleo-oceanographic data from sediment cores with geophysical observations from the subsurface, seafloor, water column, and atmosphere. My focus was on the interaction between past and present climate change and fluid flow systems on the NE Greenland Shelf, where GreenFlux yielded groundbreaking insights.

I documented the current status of permafrost and gas hydrates using a broad range of data from the shelf. Areas of elevated subsurface fluid flux were mapped using bottom-simulating reflections (BSRs), amplitude anomalies (e.g. acoustic blanking from free gas or permafrost), and gas flares, based on ~2,820 km of sub-bottom profiler and ~60,000 km of seismic data. Collaborations with the University of Tromso, GEUS (Copenhagen), VBER (Oslo)and TGS (Oslo) further enhanced data access and interpretation. The combination of seismic, hydroacoustic, and sedimentological data from all partners enabled me to do a detailed analyses of fluid sources, migration pathways, and seepage sites. However, no clear evidence of permafrost was found, and BSR observations remained inconclusive. A major component of the project was integrating sediment cores and multi-scale seismic data into a regional stratigraphic framework. I used multi-proxy records to reconstruct paleo-landscapes and Quaternary climate conditions. A recent resource assessment by GEUS, NUNAOIL, and MRA allowed linkage of seepage signals to local Jurassic and Cretaceous source rocks, tracing fluids from source to sea surface. This enabled assessment of gas hydrate stability over time. In collaboration with Shubhangi Gupta (MSCA Fellow, University of Malta), I applied a numerical fluid flow model, constrained by my stratigraphic framework and environmental parameters, to simulate hydrate evolution and seepage behavior over time.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

I combined seismic, hydroacoustic, sediment core, and remote sensing data to present the first evidence of fluid migration and natural hydrocarbon seepage from a large, active petroleum system on the NE Greenland Shelf. This region, eroded by intense glacial cycles that removed cap rocks, shows high hydrocarbon potential. Sediment cores indicate that seepage relates to Late Jurassic to Early Cretaceous source rocks. Flares detected via water column imaging and satellite imaging of oil slicks at the sea surface confirm active seepage offshore Northeast Greenland. Given the limited area surveyed, seepage is likely far more widespread. The potential release of such large amounts of hydrocarbons at the seafloor would impact on the overall functioning of the marine ecosystem and shift involved biogeochemical cycles. Implications would involve enhanced oxygen depletion and increased ocean acidification. In turn, the release of fluids with dissolved nutrients at natural cold seeps can enhance primary production. As a result, natural seepage sites on the Northeast Greenland shelf have the potential to be ‘oases of life beneath the ice’, that will use the sustained release of fluids as the base for the food web and thereby act as ‘benthic filter’.

Despite these findings, the environmental and climatic impact of fluid seepage on the NE Greenland Shelf remains poorly understood. My discoveries represent a major advance in identifying Arctic geological processes but also reveal large knowledge gaps in the geochemical and biological consequences of seepage across the region. Critical questions remain for the broader Arctic: What role do gas hydrates play? How does fluid flow respond to external forces like ocean warming or ice retreat? What governs flow in a warmer future, and what are the implications for marine systems and the global climate?