Methane dynamics a key for climate studies

Figure 1: Camille and Martin at a meeting in UIT, presenting the first results of isotopic records in the MeBo cores.
The Norcrust project attracting French students: Here is the story from two interns about Arctic paleoclimates and fluid-flow dynamic.

By Camille Labrousse and Martin Renoult

In a global warming context, the understanding of the methane dynamic in the Arctic is a key for climate studies. Focusing on the past million years, we compare the regional climatic changes with methane release events.

Our names are Martin and Camille and we are two master students from France, respectively studying in Bordeaux and Perpignan. Four months ago, we had the pleasure to be invited to work as intern students at the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) of UiT-The Arctic University of Norway in Tromsø under the supervision of Pierre-Antoine Dessandier and Giuliana Panieri (Fig. 1).

The motor of climate

As the Arctic Ocean is the motor of climate and ocean’s dynamics on Earth, it is today very important to study the impact of Climate Change in the North Pole. Thus, it is a key area to understand past and future changes, as this region is very sensitive.

We are working on the NORCRUST Project, which aims to reconstruct paleoenvironmental and paleoclimatologic conditions related to methane seepages in the Arctic Ocean. Precisely, we are studying sediment cores taken using the MeBo drilling system from Vestnesa Ridge, off the west coast of Svalbard (Fig.2). Our goal is to assess small emissions of methane by using foraminiferal assemblages and isotopic composition. Indeed, their carbonated test is built in equilibrium with pore water and record climatic and environmental changes. In methane seep sites, it can be also affected by secondary overgrowth of calcium carbonate, which is due to the interaction between the sulfate of the ocean water and methane.

Figure 2: Location map of the gravitu cores and MeBO cores on the Vestnesa Ridge (west-Svalbard).

We use a mass spectrometer to measure the isotopic values of foraminiferal tests. We are using three species: Neogloboquadrina pachyderma sinistral, Cassidulina neoteretis and Melonis barleeanum (Fig. 3) and we are looking for extremely low values of δ13C, which are directly related to methane seepages. We also investigate foraminiferal assemblages to reconstruct the distribution of fauna through time. Our work covers several millions of years and allows us to complete previous studies in this region. In order to assess the triggering processes of methane release in the region, we will compare a reference record out of the active seepage pockmarks (MeBo 126) and a gravity core (GC3) to acquire a non-affected signal of the first meters (Fig. 2). This record will provide information on regional environmental and climatic changes. The MeBo cores 125 and 127 as well as the gravity core GC2 will provide the chronology of the different methane release events that will be linked to climatic or tectonic changes.

We are enthusiastic of taking part in this project as it gives us the opportunity of getting involved in the research world and it permits us to exchange in English with scientists from different fields.

Figure 3: Melonis barleeanus, picture taken under stereoscopic microscope.