The main objective of Tara-Damocles is to reduce the uncertainty in our understanding of climate change in the Arctic concerning sea-ice cover, atmospheric key process and ocean circulation in order to improve our capability in simulating environmental change. These researches will permit to better evaluate the socio-economics impacts of a drastic retreat of the Arctic perennial sea-ice cover, or even its disappearance in a near future.
During its two-year drift among Arctic pack-ice, Tara will be the spaceship of the Damocles observing system, in charge to collect data related to sea-ice, atmosphere and ocean. Its location, in the heart of Arctic Ocean will allow to service a sophisticated autonomous buoys web, disseminated in a 500km range around the ship.Through an ambitious educational program, it also will be the opportunity to coordinated dissemination (public outreach) of scientific data collected during the whole International Polar Year (2007-2008)
SCIENTIFIC PROGRAMS developed aboard TARA
1) Meteorology and Low Atmosphere Dynamics (contact Jaak Jaagus, TU)
This program concerns the study of low atmosphere layers using two sets: a 10m mast equipped with meteorological sensors, installed on the pack-ice in the vicinity of Tara and an instrumented chain with 5 probes distributed along a 2000m long cable sustained by a 4m3 helium tethered balloon
a) 10 m mast
An Aanderaa Weather Station with sensors dedicated to the measurement and transmission of following parameters:
- Wind (speed and direction) and air temperature at 10 m
- Wind (speed and direction) and air temperature atÂ 5 m
- Wind (speed) and air temperature, atmospheric pressure and humidity at 2 m
- Wind (speed) and air temperature at 0,5 m
b) Two ultrasonic anemometers (3D) are foreseen for heat flow and momentum measurements (Metek) of two distinct zones in the vicinity of Tara.
c) A tethered balloon (Väisälä DigiCORA thethersonde) for the measurement of air temperature, humidity, atmospheric pressure, wind speed and wind direction at 6 different levels from the ice surface to 2 km of altitude. Tethered balloon usable at wind speeds not exceeding 15 m/s.
2) Radiation Balance (contacts Sebastian Gerland NPI and Jaak Jaagus, TU)
This program concerns the study of incident and reflected short, medium and long wave solar radiation and the albedo characterisation at the ice surface. Sensors will be set up on the 10-metre mast.
a) At 2 m: two pyranometers (model PSP Eppley) for the measurement of incident and reflected short wave global radiation. Two radiometers (model PIR Eppley) for the measurement of downward and upward long wave radiation.
b) Two sets of three radiometers (TriOS Ramses ACC VIS type) with a range of 320 to 950 nanometres. One set will be installed in the vicinity of Tara on the 10 metre mast, with two radiometers in the air (one directed upward, the other downward) for measurement of high spectral resolution albedo. The third radiometer will be installed in the water, below the ice, in order to measure their transmissivity through snow and ice.
Collected data will be stored on a data logger situated at the foot of the mast. Although no Argos or Iridium data transmission is presently scheduled, data will be regularly collected and diffused by Tara´s technical platform. Measuring will start in April of 2007, following Polar Night.
The three radiometers are equipped with inclinometers and a sensor dedicated to atmospheric pressure measurement. The orientation of the mast with respect to true North must be monitored regularly. This will be accomplished by positioning GPS beacons on surrounding ice floes, in the vicinity of the mast.
3) Nivology (contacts Georg Heygster UB and Florent Dominé, LGGE)
Measurement of snow density, snow thickness and snow water content.
Measurement of snow thermal conductivity incorporating surface flux in order to understand, and model, ice thickening, and brine formation.
4) Glaciology (contacts Christian Haas, AWI Jari Haapala, FIMR and David Marsan UdS)
This program concerns the dynamic and thermodynamic studies of sea-ice
Ice and snow thicknesses (EM31). A device tested in the Storfjord (Svalbard) will measure weekly ice thickness around Tara. Installed on a sledge, the EM31 device will be towed at low speed (10 km/h) on the snow covered ice floe around Tara.
Ice-mass balance throughout the drift (IMB). A device, developed by CRREL, will monitor the evolution of ice-thickness (at freeboard and keel), using thermal and acoustic sensors.
Tectonics. The aim of the project is to study the deformation (fracturing and episodic, aseismic deformation) of the sea ice cover over the scale range of 1m – 1km, from â€œin situâ€ short and long-period seismic measurements as well as displacement measurements (including GPS), over several days. These small-scale data will be compared to large-scale satellite data (10km – 1000km) to study the scaling laws associated with this deformation. This will allow us to better constrain sea ice modelling as well as the role of sea ice on the global climate. Ice field deformation will also be observed with a radar (10 km range, registration of an image each 10 mn)
5) Oceanography (contact Jean-Claude Gascard, UPMC)
Tara is equipped with a long range winch (4000 m of 5 mm cable) and an acoustic depth-finder (range 4000 m) providing daily profiles from surface to bottom (-50 m) measuring temperature, salinity and pressure and using a portable profiler (CTD Seabird SBE19). This profile will be transmitted weekly via Iridium. At the beginning of its drift, Tara will be in the relatively deep Makarov basin (>2500 m), it will later cross the 1000 m deep Lomonosov ridge and will finish its drift in the deep Amundsen and Nansen basin prior to reaching the Fram Strait.
Tara will also be equipped with a long-range (75 kHz) acoustic Doppler current profiler (ADCP) carrying out current measurements between surface and a 600 m depth. Long range (>100 km) and low frequency (780 H) acoustic propagation measurements will be made during the drift´s first months in order to establish precisely the acoustic propagation range allowing to localise the ULS floats that will be deploy during summer of 2007.
6) Atmospheric chemistry (contacts Jan Bottenheim, Canada and Florent Dominé, LGGE)
Several devices measuring and transmitting data related to surface ozone, mercury and bromide oxide concentration have been installed on Tara. A Multi Axis Differential Optical Absorption Spectroscopy (MAXDOAS) will permanently collect data. This data will contribute to monitoring of ozone and mercury levels which, according to recent observations, dramatically fall off or completely disappear with the advent of Spring. One could refer to these as â€œsurface-based” ozone holes (rather than a stratospheric ozone hole). We are convinced that this is driven by bromine atoms originating from snow or ice, which is the reason why bromine oxide content will also be measured – an excellent marker of the processes that drive these valuable observations.
Halogenated snow balance. A study of ocean-to-snow halogenated substance transfers, via pack-ice or the atmosphere, and Cl/Br fractionation
7) Solid Aerosols Automatic Trapping (contact Nadine Bernard — Besançon Univ.)..
Pollen response during Tara Drift
Pollen collecting during the drift. To carry out aero-palynologic measurements, the aspiration-based, volumetric method (Hirst method) will be performed rather than the gravimetric method based on pollen sedimentation because it allows us to link pollen or seed entrapment to temporal data.
Particles are impacted on an adhesive tape, fastened to a reel rotating at the speed of 2mm/h in front of the captor suction slot.
The pollen analysis is carried out directly on the tape with an optical microscope.
Atmospheric particle sampling and characterisation (including pollutants)
Due to harsh weather conditions, it seems difficult to use a Partisol particles pump which will need a lot of maintenance. We are currently developing an aspiration system capable of collecting and characterizing atmospheric particles (granulometry and composition) during dry and wet depositions.
8) Oceanic Chemistry (contact Catherine Pierre UPMC)
Surface water samples (10 cc) will be collected regularly in order to establish the percentage of 018 contained, thus allowing us to identify surface fresh water origin. The higher the percentage of O18/O16,, the more continental the surface fresh water origin. Surface water samples (1litre) will be also be analysed to monitor for/ determine the presence of Iode 129, released by radioactive waste recycling plants based at la Hague (France) and at Sellafield (UK).
Six to ten Nansen Bottles (1.5 l) will be used to take water samples at different depth.
9) Marine Biology (contact Benoît Quéguimeur and Ifremer)
Biodiversity of bacterial strains in the Arctic ocean
The aims of the program are; (1) to update fundamental knowledge in the field of psychrophile microorganisms (metabolic, phylogenetic, eco-physiological study, etc.) and also (2) to search for novel bioactive molecules (polyunsaturated fatty acids, cold-active enzymes, natural pigments, exopolysaccharides, etc.).
We are studying the possibility of creating a below-ice artificial reef in the vicinity of Tara in order to study the evolution of micro-organisms during spring-time planktonic bloom.
10) Zoology (contact Olivier Gilg, GREA)
a) Avifauna observation
Two sea-birds observation protocols will be realised.
The first carried out at open sea (Fall of 2006 and Summer of 2008) via strip transect, during navigation.
The second, carried out on pack-ice, at an appropriate point allowing for comparison of data with that published by Nansen in 1900.
In both, data will concern 5 species and can be realised by the ornithologist aboard.
In partnership with David Gremillet (CNRS-Centre d´Ecologie et de Physiologie Energétique)
b) Program Ivory Gull
Program developed in parallel, in Greenland and aboard Tara. Our aim is to better our understanding of this rare and discreet species, endangered at medium term due to shrinking summer pack-ice.
Small solar beacons (12g) will be used to track some individuals. In partnership with Adrian Aebischer (Friburg University, CH).
Feathers and/or blood samples will be collected from individuals and analysed by Renaud Scheifler (Besançon Univ) in order to evaluate the contamination rate by certain heavy metals.
c) Sea and Terrestrial Mammal Observation
All sea mammal observations will be documented by members of the scientific crew or, where appropriate, other crew members. In addition to sea mammals such as whale, seal, walrus, the presence of bears and arctic foxes will be documented throughout the drift. Particular attention will be paid to walrus present in the Laptev Sea and to Greenland whales present in the vicinity of the Franz-Joseph Archipelago and off Greenland itself. Biopsies will be carried out (whales) and droppings collected (walrus) for genetic analysis. (by Dr Erik Born (Greenland) and Prof. Oystein Wilg (Norway)
d) Recording Sea-mammals (hydrophone)
Below pack-ice recordings during the drift and automatic analysis of stocked sonograms will be realised. Audio bands will register the presence of right whale, narwhal, beluga whale, walrus and seal sounds. A second band will register ultrasounds (whale “clicks”)
11) Physiological Studies
Telemedicine (Dr Emmanuel Cauchy and Dr Thierry Mansir) and monitoring of the physiological stress generated in hostile and confined environments (contact Benoît Grison) throughout the drift.