MASOX - Monitoring Arctic Seafloor - Ocean Exchange

Objectives

The Arctic ESONET / EMSO site is where methane hydrate is actively dissociating. Monitoring this methane dissociation is imperative because release of methane from gas hydrate has been proposed as a key causative process for climate change and catastrophic continental margin collapse. Recent multidisciplinary research on the western Svalbard continental shelf and slope (between 78° and 80° N in the western Fram Strait) has discovered more than 250 plumes of free methane gas bubbles venting from the seabed, immediately landward of the edge of the gas hydrate stability zone (which presently lies at ~396 m water depth)(Westbrook et al., submitted). The central science objective of MASOX is to determine whether there is a causative effect of warming shallow Arctic seas conducting heat into the seafloor and subseafloor sediments that will further perturb the thermodynamic stability zone of methane hydrate, increasing the release of free and dissolved methane gas (and CO2 via redox reactions) into the ocean and atmosphere, with consequences for benthic ecology and biogeochemical cycles.

MASOX comprises research groups from AWI, IFMGEOMAR, NOC, IMR-Bergen, and University of Tromsø, bringing an integrated multi-disciplinary approach to record the physical heat flux between the ocean and sediment, the sub-seafloor hydrate phase change, and the exchange of gas and fluids between the sediment and the ocean, and associated chemical reactions. MASOX will integrate measurements of convective heat-flow and temperature recorded by CTDs and current meters, sediment heat conduction using sub-seafloor heat-flow probes, seafloor and nearbottom pH, Eh, and dissolved chemical sensors to record biogeochemistry changes, bubble detection sector scanning echo-sounders and upward looking ADCPs to document the bubble plume free-gas flux, seafloor cameras and benthic chambers to record changes in benthic ecology and chemistry, and finally, a surface buoy weather station to transmit data in realtime to shore.

 

Cartoon showing and the position of the gas hydrate stability zone (GHSZ) offshore W-Svalbard at the present day. Also shown are pathways for methane release into the water column.

Geophysical experiments will focus on the physical controls on the rate of gas venting, and apparent pulsating behaviour of the bubble plumes. Geochemical analysis of pore-waters and the water-column will assess the source of methane from dissociation and thermogenic sources, and subsequent chemical transformations that may lead to reduced levels of dissolved oxygen and increased ocean acidity. Biological experiments will assess the response of metazoan life to longterm exposure to acidic conditions at these unique methane seepage habitat sites, including a survey of non-endemic species and benthic chamber experiments. We believe this will be a world-first in sustained time-series observing of a dissociating seafloor hydrate deposit and associated chemosynthetic habitats. Most of the required sensor technology is available and proven, as is the new IMR-developed “Arctic” seafloor lander system and surface buoy system developed and used by StatoilHydro that will form the core of the observatory. Data and sensor integration will be the principal challenge of this demonstration mission, but once complete will produce a multidisciplinary, time-synchronized set of geophysical, geochemical, oceanographic, and biological data of dissociating hydrate. A key aspect of the project is the real-time serving of these data via a new project website. Such real-time data transmission, coupled with the shallow water-depth (350-400 m), offers excellent opportunities as a test-bed for “cold-seep” sensor development as it progresses from experimental design and laboratory testing to full ocean depth deployment.

The MASOX Project is planned to run for 40 months between March 2009 and August 2012, including three at-sea deployments between July 2010 and June 2012. The ESONET Demonstration Mission part of the MASOX project will extend for 20 months between March 2009 and October 2010 which includes final lander design, sensor integration, first deployment, and the first three months of the at-sea monitoring with associated real-time data serving via the web.

Relevance to objectives of ESONET NoE

The MASOX project (western Svalbard) will advance a number of the core objectives of ESONET. It will underpin the development of a seafloor observatory in the Arctic, a globally important region that is uniquely sensitive to global climate change. It will explore the links between gas hydrate stability, global climate, biogeochemical cycles, and marine ecology. It integrates cutting-edge lander technology provided by an existing ESONET partner with state-of-the-art sensor systems. It involves a substantial in-kind contribution from an industrial partner that will ensure a high degree of standardisation and interoperability between academia and industry. It will demonstrate the capability of seafloor monitoring with realtime data transmission, via satellite, from remote, high-latitude sites. Finally it adds significant value to an existing designated ESONET site and will provide “critical mass” of multi-disciplinary research worthy of installing a future multi-node, cabled observatory system as envisaged by EMSO.

All global climate change scenarios (with CO2 concentration increasing to at least 500 ppm), forecast large and irreversible change in the Arctic Ocean. Coupled ocean – atmosphere modelling (e.g., the CHIME model) predicts warming of shallow Arctic seas by +5°C and +14°C for surface-waters by the year 2100. Indeed, direct observations of upper-waters (at 250 m water-depth) in the western Fram Strait, record a ~+1°C increase between 1998 and 2006 (Schauer et al., 2008). Recent marine geophysical research has identified methane hydrate in the Arctic Ocean (including west of Svalbard) (e.g., Posewang and Mienert, 1999), and determined some bounds of their thermodynamic stability (Haacke et al., 2008). Recent discoveries show the Svalbard site to be venting methane as free gas where the hydrate outcrops at the seafloor at a water-depth of 350-400 m (Westbrook et al., submitted).

 

 

Warming of West Svalbard Current (WSC) of ~+1°C from 1998-2006

Arctic ESONET/EMSO site (yellow circle), western Fram Strait, and proposed MASOX site.

The central science objective of MASOX is to determine whether there is a causative effect of warming shallow Arctic seas conducting heat into seafloor and sub-seafloor sediments at such a rate that the thermodynamic stability field of methane hydrate will be perturbed, increasing the release of free and dissolved methane gas (and CO2 via redox reactions) into the ocean. The impacts of methane release on benthic ecosystems and ocean biogeochemical cycles will also be assessed. Such causal relationships between climate change and catastrophic methane release have been proposed for the geological past (e.g., Kennett et al. 2003) and for changes in atmospheric methane in the northern hemisphere in particular over the last 45 kyrs (Maslin et al., 2004). Tackling such a science question requires a multidisciplinary approach over an extended time interval to record the physical heat flux from ocean to sediment, the sub-seafloor hydrate phase change, and then the reversal of the physical flux (as free gas plumes) from the sediment to the ocean, together with associated chemical reactions. Accordingly, MASOX will integrate measurements of convective ocean-flow and temperature using CTDs and current meters, sediment heat conduction using sub-seafloor heat-flow probes, seafloor and near-bottom pH, Eh, and other chemical sensors to monitor chemical fluxes and transformations, bubble detection sector scanning echo-sounders and upward looking ADCP’s to document the bubble plume free-gas flux, seafloor cameras and benthic chambers to record changes in benthic biota, and finally a surface buoy weather station to transmit data in real-time.

This is an ambitious integrative science project to document state transformations and physical / chemical fluxes between the lithosphere and hydrosphere. We believe this project will be a world-first in sustained seafloor monitoring of a dissociating methane hydrate deposit. Most of the required sensor technology is available and proven, but considerable effort and coordination will be required to integrate all these sensor systems within a linked seafloor lander – surface buoy system, that includes the necessary data and power management systems, sampling methodologies, and data transmission protocols. Data integration will be one of the main challenges of this demonstration mission, but also probably the most effective tool to speed scientific integration between the teams. The end product will be a multidisciplinary, synchronized, time-series of set of data produced by connected and autonomous instruments, with time as the only common variable. These data will allow us to identify variations in methane hydrate dissociation and to determine relationships of methane release and impact to climate change. Though we plan to run MASOX for at least two years (contingent on success in ship-funding requests), with the proposed ESONET Demonstration Mission being the first three months of the two year deployment, we expect to record temporal differences not only on time-scales of years due to climate change, but also effects due to seasonal 1-1.5°C variations in bottom-water temperature. Cognizant of the importance of the science and technology integration required for the MASOX project, five of the seven project workpackages within the project address these issues, comprising WP1 Sensor development and lander infrastructure, WP2 Geophysical experiments, WP3 Geochemical and flux experiments, WP4 Biological / oceanographic experiments, and WP5 Data protocols and management.

An important part of MASOX project is the inclusion of the Institute of Marine Research – Bergen (IMR). IMR have had no previous engagement with ESONET (and are not ESONET partners), though the group are world-leading engineers of lander systems with unique expertise in novel data management IP systems, surface buoy wind generation and battery storage, adaptive sampling strategies and power-use management, high-latitude deployments, and real-time data transmission. The inclusion of IMR in MASOX will widen and integrate the technology base within the ESONET NoE. Similarly, IMR will benefit from the use and adaptation of NOC and GEOMAR sensors into their lander system, with the prospect of enhanced and increased usage in Arctic Ocean observing. Under the auspices of MASOX, IMR will apply to be an ESONET partner, though success of the MASOX project is not contingent on them being so. For the purposes of this proposal and project contracting, IMR will be funded through NOC using accepted EU / ESONET sub-contracting regulation and practice.
Though most technology exists, the MASOX observatory will also offer excellent opportunities as a test-bed for sensor development as sensors progress from experimental design and laboratory testing to full ocean-depth deployment. The relatively shallow depth (350-400 m) and real-time data transmission provide a prime opportunity for staged sensor development and data validation. For example, NOC will add new prototype methane and CO2 sensors to the MASOX lander in the second year of the proposed project programme, before deployment as full ocean-depth sensors and
housings at other sites.