Azores Observatory – Atlantic Ocean
The Azores and Mid-Atlantic Ridge area has special habitats associated with hydrothermal
vents and sea floor morphology is distinct with recent crust spreading from the mid ocean
ridge axis.
Scientific context and relevance
The MOMAR (“Monitoring the Mid-Atlantic Ridge”) project was initiated by the international
InterRidge Programme, to study active mid-ocean ridge processes along a slow-spreading ridge
segment (Lisbon, 1998). The goal is to promote and establish a coordinated and multidisciplinary
long-term study of hydrothermal environments at the Mid-Atlantic Ridge (MAR) near the Azores
(35°N to 40°N).
Hydrothermal circulation at mid-ocean ridges is a fundamental process that impacts the transfer of
energy and matter from the interior of the Earth to the crust, hydrosphere and biosphere. Seawater
circulates through the permeable upper oceanic crust at mid-ocean ridges, exchanges chemicals with
the surrounding rocks, and is heated up to temperatures of a few hundred degrees Celsius. This hot
fluid flows up and is expelled at hydrothermal sites, in the form of black smokers, or diffuse vents.
The unique faunal communities that develop near these vents are sustained by chemosynthetic
microbes that use the chemicals in the hot fluids as a source of energy.
Scientific objectives
The objective of the MOMAR project is to study the temporal variability in active processes such as
hydrothermalism, ecosystem dynamics, volcanism, seismicity and ground deformation, in order to
constrain the dynamics of mid-ocean ridge hydrothermal ecosystems:
•
What are the feed-backs between volcanism, deformation, seismicity, and hydrothermalism?
•
How does the ecosystem couple with sub-surface processes?
•
What are the mass, energy and biological fluxes at hydrothermal vent fields?
The implementation plan includes a multi-scale approach, ranging from the regional (>100 km) scale
for seismicity, oceanography, and biological dispersion, to local (1 km) and very local (<1m) scales
for the vent field and its ecosystem. The regional scale approach adresses fundamental issues such
as:
. the relation between intermediate depth hydrothermal fields, seamount ecosystems, and the
evolution of fishing resources in the Azores area,
. seismic and volcanic risks to populated areas in the Azores Islands,
. and the movement of deep water masses and the consequences of changing thermohaline
circulation in the North Atlantic on climate and on biodiversity.
The planned regional seafloor system of geophysical observing sites will also be an important
European contribution to the global network of seismic and magnetic observatories that is currently
implemented to study the physics and chemistry of the Earth’s deep interior.
The MAR near the Azores is ideally located for this marine multidisciplinary observatory project: it
is near port (Horta on Faial Island; Figure 2), allowing for short transit times for the deployment and
retrieval of tools, and making cable connection to shore an option for later stages of implementation
of the project.
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Azores Observatory – Atlantic Ocean
The MAR near the Azores comprises 4 known hydrothermal vent fields, each with its own specific
geological, chemical, hydrothermal, volcanic and biological characteristics (Lucky Strike, Rainbow,
Menez Gwen, and Saldanha). It has been the focus of a great number of cruises in the past few years,
as part of the FARA program (French-American Ridge Atlantic), the MARFLUX (MAST II EC
program), AMORES and ASIMOV (MAST III EC program) and VENTOX (Framework V),
EXOCET/D (Sarradin et al, 2005) and MoMARNET (Framework VI; Cannat et al., 2006) European
projects. The geological-geophysical background of this region is well constrained, as are the
general characteristics of the known hydrothermal vents, and the broad diversity of the associated
ecosystems.
The II and III MoMAR Workshops that took place in Horta, Azores (June 2002) (Santos et al, 2002),
and in Lisbon (April 2005) provided an implementation plan for integrated studies and long-term
observations in the MoMAR area. A list of critical experiments and an adequate order for
implementation were established (all MOMAR workshop reports are available at www.momar.org).
Following the II Workshop, the European scientific community coordinated several cruise
proposals, and two EC proposals that have since been funded, one for development of observatory
sensors (EXOCET/D; Sarradin et al., 2005), and the other a research and training EC network
(MoMARnet; Cannat et al., 2006). A more recently funded FP6 project, NERIES, also includes
MoMAR as one of its target sites for the long-term installation of a broad band Ocean Bottom
Seismometer.
The MoMAR ESONET node. Outline of the implementation plan
Inside the MoMAR area, the Lucky Strike hydrothermal field (~37°37’N / 32°17’W) is the main
target of the MoMAR ESONET node. Discovered in the nineties (Langmuir et al., 1997) this field
has since been the object of many cruises, addressing its geological and geophysical characteristics
(Detric et al., 1995; Cannat et al., 1999; Escartin et al., 2001; Miranda et al., 2005; Fouquet et al.,
1995; Ondreas et al., 1997), as well as fluid chemistry and vent field biology (Desbruyères et al,
2001). Over 100 hydrothermal vents are distributed on the summit of a large axial volcano. Vent
fluid temperatures range from the 330º C of black smokers, to low (200-212ºC), and very low (<
20ºC) temperature fluids (Von Damm et al., 1998; Cooper et al., 2000). Fluid temperatures at some
vents appear to be very stable over a time scale of a few years (i.e., Tour Eiffel, 324±1°C), while
others show variability of >10°C (Statue of Liberty, 202-185°C; Sintra, 176-215°C; Charlou et al.,
personal communication). A recent seismic exploration (SISMOMAR cruise; PI W Crawford) was
able to identify the seismic signature of the axial magma chamber below the hydrothermal field,
which is most likely the heat source for the Lucky Strike hydrothermal system.
Long-term acoustic monitoring of the seismic activity (since 1999) of the Mid-Atlantic Ridge by
networks of autonomous hydrophones moored in the SOFAR channel has demonstrated the
usefulness of acoustic monitoring sensors deployed in the water column (e.g. Smith et al. 2002,
Goslin et al. 2004). On average, due to the low attenuation of acoustic waves along their paths in the
SOFAR channel, hydrophones are able detect 20 to 50 times more earthquakes than land-based
networks (Figure 13) and provide better accuracy on their location (1-2 km error for events located
within an hydrophone array). In July 2005, a network of 4 hydrophones has been specially deployed
for a continuous monitoring of the low-magnitude seismic activity in the MoMAR sector at a
regional scale (from 32°N to 39°N). This array will be turned-over in April 2006 for another year of
monitoring (MARCHE cruises, PI J. Goslin). This hydroacoustic monitoring effort will provide the
first long time-series of observation from the MoMAR observatory. Beyond 2007, real-time
seismoacoustic monitoring will be a key issue for assessing the tectonic/magmatic/hydrothermal
potential of future earthquake activity.
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Azores Observatory – Atlantic Ocean
The objective for the Lucky Strike MoMAR node is to set up a permanent seafloor observatory to
record and relate seismicity, seafloor deformation, fluid flow, temperature and composition, with the
dynamics of vent communities (including microbes).
Implementation of the Lucky Strike MoMAR observatory has begun in 2005-2006 for seafloor
deformation, near vents faunal communities monitoring, vent fluid temperature, and seismicity, with
cruises funded primarily through the French system, with additional support from the EC FP6
EXOCET/D, and NERIES projects.
In a first stage, sensors will be autonomous or linked acoustically to an ASSEM junction box
equipped with messengers for periodic satellite data transmission to shore (Stage 1).
Observatory experiments are presently planned for periods of 2 to 5 years, but decadal monitoring is
aimed at, as it is the most adapted to the time scale of active processes in this ridge environment.
Figure 1 : Earthquake epicenters identified along the Mid-Atlantic Ridge north and south of the Azores
Plateau between June 1, 2002 and March 15, 2003. Black dots are the 1906 events recorded by the networks of
autonomous hydrophones (deployment sites are the yellow stars and circles); white triangles are the 40 events
recorded by land-based networks during the same period (NEIC catalog). As part of the MoMAR observatory, a
network of 4 hydrophones was deployed around the MoMAR site (37N, 32W) in July 2005 for a period of two
years (MARCHE cruises, PI J. Goslin).
The longer term objective (>2008) is to implement an integrated monitoring infrastructure with real
time data satellite transmission (stage 2), followed (>2012) by cable energy supply and data
transmission (stage 3). It is envisioned that these later phases of the project should see an extension
of real time monitoring to volcanic, hydrothermal and biological processes on the Azores Platform.
This extension to nearer to shore active volcanic domains and biological hot spots will address the
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Azores Observatory – Atlantic Ocean
issues of volcanic and seismic hazard to the densely populated areas of the Azores Islands, and assist
the Azores region for the durable management of its fishing resources.
Existing national and international programs on the site
Teams involved in the MOMAR project belong to 32 leading institutions corresponding to 9
European countries. Most have long experiences in seagoing operations, deep-sea experimentation
and scientific and technological development. For many, the MoMAR project represents the exciting
continuation of ongoing research efforts in the MAR - Azores Triple Junction region, with
significant support through FP3, FP4 and FP5 programs, and from national funding agencies
particularly in Germany, France, UK and Portugal. A few US colleagues are also involved in the
planning, through the InterRidge Program. Although no US proposal has been funded so far, the
involvement of these colleagues could lead to a formal EC-NSF agreement for the funding of the
project in the years to come.
Two EC-FP6 projects directly concern the MoMAR project: one for development of observatory
sensors (EXOCET/D; Sarradin et al., 2005), and the other a research and training EC network
(MoMARnet; Cannat et al., 2006). A more recently funded FP6 project, NERIES, also includes
MoMAR as one of its target sites for the long-term installation of a broad band Ocean Bottom
Seismometer.
A land-based laboratory, LabHorta, is installed at DOP-UAç (Colaço et al, 2002), at close proximity
to the MoMAR area and the active deep-sea vent sites. LabHorta was conceived in view to keep
with live vent animals recovered from acoustically-retrievable cages, developed during VENTOX
project, at the deep-vents of the area. LabHorta is currently being equipped with resident pressure
vessels among other improvements funded through the Portuguese and Azorean research councils.
MoMAR has been identified as a priority project both by Ifremer and by CNRS-INSU in France,
and a french MoMAR steering committee (chaired by M. Cannat) has been nominated in July 2004
to coordinate national initiatives and to link with European and international observatory programs.
Five MoMAR-related french cruises are funded for the 2005-2007 period. Substantial funding for
MoMAR cruises and experiments in France also comes from the newly created Agence Nationale de
la Recherche (ANR).
The MoMAR approach follows the recommendations of the recent Quality Status Report on
ecosystems of the oceanic north Atlantic, issued by the OSPAR´2000, that calls for a coordinated
program of species identification and distribution mapping, all set in the context of a full suite of
environmental and habitat parameterization.
Last but not least, the Regional government of the Azores sponsors an International workshop
involving leading scientists and stakeholders regarding aspects of the hydrothermal vent field
conservation (Santos et al, 2003). In October 2006 the OSPAR WG on Marine Protected Areas
Species and Habitats (MASH) adopted the proposal made by Portugal/Azores in view to include the
deep vent sites Rainbow, Lucky Strike and Menez Gwen (MAR) in the OSPAR network of MPAs.
The sites were proposed “with the aim of promoting knowledge, monitoring and conservation of an
area that best represents species, habitats and ecological processes in deep-sea hydrothermal vents in
the OSPAR area, while enabling sustainable scientific research and promoting education and
environmental public awareness and interest”. This situation creates a unique opportunity to link
science, education and environment protection.
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Azores Observatory – Atlantic Ocean
The proposed research and development effort brings together teams with complementary expertise
in the fields of marine earth, ocean and life sciences, and of marine technology. As such, this project
mobilizes a community that is larger than the forces of any one country within Europe. It takes
advantage of the great opportunities offered by the Azores MAR region and builds upon many years
of research led by European teams in the area. The ESONET NoE will represent a great opportunity
to integrate more fully the wide range of marine scientific and technological expertise that exists
within Europe, and to coordinate the MoMAR initiative with actions planned at other European sub
sea observatory nodes for a greater scientific and societal impact.
Participants:
University of Azores
University of Lisboa
Ifremer
KDM/University of Bremem
Selected References for Node description and participants:
Cannat, M., A. Briais, C. Deplus, J. Escartín, J. Georgen, J. Lin, S. Mercouriev, C. Meyzen, M.
Muller, G. Pouliquen, A.Rabain, and P. da Silva (1999), Mid-Atlantic ridge - Azores hotspot
interactions: Along-axis migration of a hotspot-derived magmatic pulse 14 to 4 myrs ago, Earth
Planet Sci. Lett., 173, 257-269.
Cannat, M., Le Bris, N., Santos, R., Miranda, J.M., Holm, N., Dubillier, N., Favali, P., Connelly, D.,
Schultz, A., Dando, P., Garcia, R., Dehairs, F., Tarits, P., and F. Gaill. 2006. MoMARnet:
Monitoring deep sea floor hydrothermal environments on the Mid Atlantic Ridge: A Marie Curie
Research Training Network funded by the European Commission. Geophysical Research Abstracts,
EGU SymposiumVienna.
Colaço, A., R.S. Santos & VENTOX party. 2002. LABHORTA - a land-based laboratory for vent
studies. P. 36 in R.S. Santos, J. Escartín, A. Colaço & A. Adamczewska (Eds). 2002. Towards
planning of seafloor observatory programs for the MAR region (Proceedings of the II MoMAR
Workshop). Arquipélago. Life and Marine Sciences. Supplement 3: XII + 64 pp.
Cooper, M. J., H. Elderfield, and A. Schulz (2000), Diffuse hydrothermal fluids from Lucky Strike
hydrothermal vent field: Evidence for a shallow conductively heated system, J. Geophys. Res., 105,
19369-19375.
Desbruyères, D., Biscoito, M., Caprais, J.-C., Comtet, T., Colaço, A., Crassous, P., Fouquet, Y.,
Khripounoff, A., Le Bris, N., Olu, K., Riso, R., Sarradin, P.-M. & Vangriesheim, A. 2001.
Variations in deep-sea hydrothermal vent communities on the mid-Atlantic Ridge when approaching
the Azores Plateau. Deep-Sea Res 48 (5): 1325-1346.
Detrick, R. S., H. D. Needham, and V. Renard (1995), Gravity anomalies and crustal thickness
variations along the Mid-Atlantic ridge between 33°N and 40°N, J. Geophys. Res., 100, 3767-3787.
Escartín, J., M. Cannat, G. Pouliquen, A. Rabain, and J. Lin (2001), Crustal thickness of V-shaped
ridges south of the Azores; interaction of the Mid-Atlantic Ridge (36 degrees -39 degrees N) and the
Azores hot spot, JGR, 106, 21719-21735.
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Fouquet, Y., H. Ondreas, J. L. Charlou, J. P. Donval, J. Radford-Knoery, I. Costa, N. Lourenço, and
M. K. Tivey (1995), Atlantic lava lakes and hot vents, Nature, 377, 201.
Langmuir, C., et al. (1997), Hydrothermal vents near a mantle hot spot: the Lucky Strike vent field
at 37°N on the Mid-Atlantic Ridge, Earth Planet Sci. Lett., 148, 69-91.
Miranda, J. M., J. F. Luis, N. Lourenço, and F. M. Santos (2005), Identification of the magnetization
low of the Lucky Strike hydrothermal vent using surface magnetic data, J. Geophys. Res., 110,
B04103.
Ondreas, H., Y Fouquet, M Voisset, & J. Radford-Knoery (1997), Detailed study three contiguous
segments of Mid-Atlantic Ridge, South of the Azores (37-38.5N), using acoustic imaging coupled
with submersible observations, MGR, 19, 231-255.
Santos, R. S., J. Escartin, A. Colaço & A. Adamczewska (Eds.) 2002. Towards planning of seafloor
observatory programs for the MAR region (Proceedings of the II MoMAR Workshop). ArquipélagoLife and Marine Sciences. Supplement 3: xi + 64pp. (ISBN: 972-8612-11-7)
Santos, R. S., A Colaço & S Christiansen (Eds.) 2003. Planning the Management of Deep-sea
Hydrothermal Vent Fields MPAs in the Azores Triple Junction (Workshop proceedings).
Arquipélago – Life and Marine Sciences, Supplement 4: xi + 64pp. (ISBN: 972-8612-14-1)
Sarradin P.-M., Sarrazin J., Sauter E., Shillito B., Waldmann C., Olu K., Leroy K., Colaço A. & the
Exocet/d consortium, 2005. Extreme ecosystem studies in the deep ocean:technological
developments EXOCET/D Geophysical Research Abstracts, Vol. 7, 03257.
Von Damm, K. L., A. M. Bray, L. G. Buttermore, and S. E. Oosting (1998), The geochemical
controls on vent fluids from the Lucky Strike vent field, Mid-Atlantic Ridge, Earth Planet Sci. Lett.,
160, 521-536.
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