RRS James Clark Ross JR20110715 (JR253)
Cruise summary report
| Cruise Info. | |
| Ship name (ship code) | RRS James Clark Ross (74JC) |
| Cruise identifier | JR20110715 (JR253) |
| Cruise period | 2011-07-26 — 2011-08-25 |
| Status | Completed |
| Port of departure | Glasgow, United Kingdom |
| Port of return | Longyearbyen, Svalbard and Jan Mayen |
| Purpose | Research |
| Objectives | 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 predict warming of shallow Arctic seas by +5C and +14C 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 ~+1C increase between 1998 and 2006. Recent marine geophysical research has identified methane hydrate in the Arctic Ocean (including west of Svalbard) and determined some bounds of their thermodynamic stability. Recent discoveries show the Svalbard site to be venting methane as free gas (into at least the lower water-column) where the hydrate outcrops at the seafloor at a water-depth of 350-400 m. A crucial unknown science question is to determine whether there is a causative effect of warming shallow Arctic seas that will perturb the stability of sub-seabed gas hydrates leading to different / faster dissociation fluxes and / or processes?
The critical unknowns in methane dissociation processes in shallow Arctic seas are: (1) what is the volume / inventory of sub-seabed methane hydrate of Arctic continental shelf and slopes? (2) what is the volume / inventory of free methane gas beneath the hydrate? (3) what are the mechanisms, and physical - chemical processes that releases free gas from hydrate? (4) what is the flux, physical state, and chemical fate of methane vented from the seafloor? (5) what is the flux of free methane venting to the atmosphere? Within the Arctic, the western Svalbard shelf and slope is sited at a critical location. The site is bathed by a northward flowing filament of the North Atlantic Current that is a crucial "barometer" of global ocean warming, which shows evidence of warming (and localised cooling) over time scales of years, and is an area of known methane venting with over 250 individual gas bubble plumes ascending through the water-column (with the pre-dominant majority located at the immediate landward edge of the gas hydrate stability zone at ~396 m water depth). The main JCR253 cruise objectives were to: (1) service the AOEM / MASOX seafloor lander with data downloading and installation of replacement batteries and subsequent redeployment at the site (2) undertake acoustic mapping of ascending gas plumes along the western Svalbard slope (3) undertake seafloor ROV and side-scan mapping of seafloor "vent" sites along the western Svalbard slope (4) undertake CTD survey and biogeochemical analysis of water-column around AOEM site and along the western Svalbard slope (5) undertake sediment coring and biogeochemical analysis of sediments and pore-water around AOEM site and along the western Svalbard slope (6) undertake ship-board meteorological and air-sampling measurements during the cruise. The cruise completed all objectives with the recovery and redeployment of the AOEM / MASOX lander, deployment and recovery of the BOB lander for a 17 day experiment, integrated seafloor and water-column sampling along three transects that cross the known gas - hydrate stability zone boundary at the 400 m water-depth, and extensive hydro-acoustic mapping of new methane gas flares where acoustic bubble plumes ascend to the sea-surface - with this newly discovered shallow venting extensively sampled with water-column sampling, sea-surface air sampling, and HyBIS video imaging of the seafloor venting. |
| Chief scientist | Ian Wright (National Oceanography Centre, Southampton) |
| Project | Oceans2025 and ESONET |
| Coordinating body | Natural Environment Research Council 9NERC) and European Union (EU) |
| Cruise report |  (17.32 MB) |
| Ocean/sea areas | |
| General | Norwegian Sea Arctic Ocean |
| Specific | Northern Norwegian Sea and Arctic Ocean |
| Measurements | |
| Physical oceanography | |
| Water bottle stations | Quantity: number of profiles = 58 Description: CTD and water sampling. CTD measures conductivity, temperature and depth. Nature of data: chemical composition of seawater samples. Parameters measured: methane, ammonia and oxygen concentration. Further analysis: nutrient concentrations. |
| CTD stations | Quantity: number of profiles = 58 Description: CTD and water sampling. CTD measures conductivity, temperature and depth. Nature of data: chemical composition of seawater samples. Parameters measured: methane, ammonia and oxygen concentration. Further analysis: nutrient concentrations. |
| Current profiler (eg ADCP) | Quantity: activity duration in hours = 250 Description: Broadband ADCP. Frequency: 75kHz. Parameter measured: vertical current profiler, continuous recording. |
| Meteorology | |
| Atmospheric chemistry | Quantity: number of samples = 36 Description: Air sampling. Frequency: daily. Nature of data: methane concentration and carbon isotope composition. Parameters measured: wind speed and direction, air temperature, air pressure. |
| Geology and geophysics | |
| Grab | Quantity: number of cores = 13 Description: Box coring, discrete sampling for chemical composition of sediment and porefluids. Parameters measured: methane, alkalinity, ammonia concentration in porefluid. Further analysis: concentration of anion and cations in porefluid; chemical composition of sediments. |
| Core - soft bottom | Quantity: number of cores = 20 Description: 6 gravity and 14 piston cores, discrete sampling for chemical composition of sediment and porefluids. Parameters measured: methane, alkalinity, ammonia concentration in porefluid. Further analysis: concentration of anion and cations in porefluid; chemical composition of sediments. Gravity coring was use while piston core was being fixed. |
| Bottom photography | Quantity: number of dives = 24 Description: Tethered HyBIS / ROV dives. One dive has the purpose of checking the system and purging the air from hydraulic system; one dive was meant to look for MASOX lander; 4 dives were for recovering the lander, one to examine BOB site, one to lay the thermistor string from MASOX lander and 13 to perform video mapping discovery dives on plume sites and undertake vent fluid sampling and bubble counting, and 4 dives to undertake video transect mapping and grab sampling. . For 10 of them the video was recording. All dives had one or more HyBIS video cameras recording |
| Single-beam echosounding | Quantity: number of profiles = 20 Description: 10 hours. TOPAS. Frequency: 3-6 kHz. Parameter measured: continuous sub-bottom vertical acoustic signal profiler. |
| Single-beam echosounding | Quantity: number of profiles = 220 Description: 530 hours. EK60. Frequency: 38, 120 and 200 kHz. Parameter measured: single beam continuous water column vertical profiler. |
| Multi-beam echosounding | Quantity: number of profiles = 201 Description: 650 hours. EM122. Frequency: 12 kHz. Parameters measured: multi-beam continuous water column vertical profiler and bathymetry measurement. |
| Moorings, landers, buoys | |
| Geology and geophysics | |
| In-situ seafloor measurement/sampling | 78° 33' 16" N 9° 28' 35" E — BOB (Bubble Observatory): Autonomous free lander to monitor bubble sources with an ER60 120kHz echo-sounder. Deployed on August 6th at 17:00 GMT in 387 m water-depth and successfully recovered on August 23th 2011 |
| Single-beam echosounding | 78° 33' 16" N 9° 28' 35" E — BOB (Bubble Observatory): Autonomous free lander to monitor bubble sources with an ER60 120kHz echo-sounder. Deployed on August 6th at 17:00 GMT in 387 m water-depth and successfully recovered on August 23th 2011 |
