Partners are “CAGE – Center for Arctic Gas Hydrate, Environment, and Climate” at the University of Tromsø, Migris AS, Statoil ASA, Lundin Norway AS, and ENI Norge.
NORCRUST aims to study natural methane seepage sites at the seabed of the Norwegian-Barents seas by integrating geological, geochemical, and biological data. NORCRUST wants to understand the dynamics and history of these fluid flow systems and its control factors.
This requires knowledge of timing of hydrocarbon migration to the seafloor, ability to distinguish hydrocarbon origin from shallow biogenic and deep thermogenic sources, and reliable assessment of the temperature and depth of hydrocarbon formation.
NORCRUST will provide this knowledge by applying recent technological and scientific advances on methane-derived carbonate crusts formed at seepage sites and gas-impregnated sediments during active leakage of hydrocarbons. We have been using remotely operating vehicles (ROV) to inspect the seafloor and sample carbonate crusts, gas bubbles released from the seafloor and surrounding sediments.
In 2017, NORCRUST will explore recently discovered canyons along the Lofoten margin on board research vessel G.O. Sars. The video recorded from a natural methane seepage site northwest off Svalbard illustrates the technical operations during the seafloor sampling. From the ROV, we sample natural methane seep sites which are evident on the seafloor by the presence of methane oxidizing bacteria (white spots). Parallel we sample carbonate crusts, which are visible at the seafloor apparently as hard rocks colonized by various organisms, however, formed during the bacterial consumption of sulphate and methane close to the seafloor. The abundance of high methane concentration below the seafloor is evident by the release of free gas bubbling into the water column during sampling . All sampled material is collected in baskets at the seafloor and will be brought up to the research vessel for further inspection and detailed analysis.
The expected results will help to better characterize the origin of the seeping methane and the geological history, why and when methane was released into the water column and eventually to the atmosphere.
NORCRUST collaborates with world-leading research institution in the field of stable isotope geochemistry, U-Th geochronology, mineralogy and petrography. The principal researchers within NORCRUST are Jochen Knies, Aivo Lepland, Terje Thorsnes (NGU), and Giuliana Panieri (CAGE-UiT). Post Doc fellows are Tobias Himmler, Wei-Li Hong, and Pierre Antoine Dessandier. The project started in 2016 and will last until 2020.
Norcrust-cruise with G.O Sars:
G.O. Sars cruise "NGU PL-1710, logbook.
Day 6, 12.08.17
Finally, after 5 quite successful days the drama started on the last day. The ROV was supposed to be launched at around midnight when the weather said STOP. Strong winds and >3 m high waves made the operation impossible. The ROV crew stopped the operation and we decided to leave the Hola area and steamed back home to Tromsø. The immediate reaction was disappointment, but we realized immediately that this was the right decision. We arrived in Tromsø at lunch time. Cleaning the lab (Figure 1), group photo (Figure 2), unloading equipment and samples kept us busy for the rest of the day. The cruise officially ended in the afternoon and I am grateful to the captain Hans Troland and his crew and the ROV crew with Stig Vågenes for a wonderful and intense week on G.O. Sars.
Best wishes, Jochen
Day 5, 11.08.2017
On day 5 of our scientific program, we mapped a second canyon with the multibeam system mounted on ROV Ægir 6000. Also in this canyon we found evidence for lithified sandstones cropping out along the steep walls of the canyons. The sandstones were sampled in the first canyon and will be prepared for age determination in our laboratories. The canyon walls are plastered with bacterial mats, carbonates and a biological community known from other seep sites in the Arctic (Figure 1).
Unfortunately, these steep walls were difficult to sample and only two push cores were retrieved. We focused the sampling program on easily accessible areas within the canyon and took a number of carbonate crust samples and push cores. The program in the study area was concluded by a shallow seismic (TOPAS) survey.
Now, we are heading north and will stop at the Hola seep site off the Vesterålen coast. There we will perform a detailed multibeam survey and try to get a free gas sample from the bubbling seabed. In the meantime, the discussion of how to proceed with the new push cores and what measurements will be conducted in the future is on (Figure 2)!.
This is far from being easy and keeping the overview is apparently my most important job during these exciting days ().
Still in good mood and looking forward to be in Tromsø again on Saturday evening.
Day 4, 10.08.2017
The scientific program of Day 4 started early. Around 4 am the ROV was launched at a spectacular site with a large number of bacterial mats and carbonate crusts (Figure 1).
We collected 9 push cores and several carbonate crusts in a basket that was placed at the seafloor in order to keep the ROV "at work" (Figure 2).
Once the basket was full, it came on deck and the scientific party began (Figure 3).
The push cores are sampled for porewater to trace geochemical processes related to fluid flow processes. Samples are also taken for gas measurements to determine the amount and its sources. The response of the biological community on methane seepage will be analyzed by means of planktic and benthic foraminifera. All carbonate crusts samples were documented onboard, however, the analytical program starts when the samples are in our laboratories. We also tried the gravity coring system to study the longer geological history in the study area. Unfortunately, the seabed in this region is very heterogeneous and no soft sediments were founds. Although the core liner penetrated the sediment surface, only a few sandy-rich carbonate pieces were recovered. Today will most likely be the last day of intense sampling. Tomorrow, we expect a storm in our study area after lunch and no more ROV work will be possible. Despite the long days, the group works very well together.
Day 3, 09.08.2017
On Day 3, we finished the multibeam bathymetric survey of the ROV (Figure 1). The new map revealed interesting features beyond the presence of carbonate crusts, tube worms, and bacterial mats. Our first tentative interpretation indicates that bedrock is cropping out and that fluid flow features are mainly restricted to one area within the canyon. A video mosaic was generated above the fluid flow features to map the biological communities. This work finished early in the morning. Now, the ROV crew around Stig Vågenes is preparing the ROV for the sampling at the seafloor. A basket will be launched together with the ROV in order to store temporarily the collected material. During the first dive, we collected 5 carbonate crusts and 5 sediment push cores (Figure 3). Besides the science, our CAGE communication officer Maja Sojtaric takes care of the public outreach programme. On a sunny day like this, filming the action onboard is a pleasure.
Day 2, 08.08.2017
We reached our target area in the morning of 08.08.2017. The sea is still calm and the weather is excellent for ROV operations. Geochemical and micropaleontogical laboratories are ready for sampling (Figure 1). Here, we will measure the alkalinity and the iron concentration within the porewater samples. This will give us a first glimpse on the activity of the fluid flow system in the canyons. All other measurements including methane gas concentration will be done in laboratories at home and with our NORCRUST partners. Around 09.30 am, the first CTD cast was deployed for calibration purposes of the ROV Ægir 6000 (Figure 2). Thereafter the multibeam bathymetric survey started. The new data will have a resolution of less than 20 cm and will help us to define the sampling sites (Figure 3).
Day 1, 07.08.2017
The scientific party entered G.O. Sars in the early morning of 07.08.2017. We are four scientists from NGU (Jochen Knies, Aivo Lepland, Wei Li Hong, and Tobias Himmler), four scientists from CAGE-UiT (Arunima Sen, Haoyi Yao, Pierre-Antoine Dessandier and Kasia Melaniuk) as well as CAGE communication officer Maja Sojtaric. The Captain Hans Troland briefed us about the security system onboard, while a guided tour was given by the Chief Officer. The morning was used to unpack and store the equipment properly in the laboratories onboard G.O. Sars. A fire drill interrupted the lunch and coffee break. During the afternoon, Jochen introduced the goal and objectives of the cruise. The cruise is sponsored by the NFR Petromaks 2 NORCRUST project and its partners. The target area lies southwest of the Lofoten/Vesterålen and is situated along the continental margin at 750 m water depth. Two small canyons will be inspected for active fluid flow by ROV operation. Active fluid flow has been inferred from the presence of methane-derived authigenic carbonates and bacterial mats recorded in the frame of the MAREANO programme. We spent the afternoon in preparing the multibeam bathymetric survey with the ROV Ægir. Several lines will cover the southernmost canyon where we expect the presence of the fluid flow features. From the new bathymetric map with less than 20 cm resolution we will define the sampling sites for carbonate crust sampling, pushcoring, and free gas sampling. We will also sample the seabed with the gravity coring system onboard G.O. Sars. More exiting stories are soon to be published.