of high-intensity gas seeps in the Black Sea to methane emission to the
The innovative aspects of the project
Graphical presentation of the project's components
CRIMEA project aims at establishing a budget of methane release to the atmosphere
related to high-intensity outbursts of methane at the seafloor of the Black
Sea, and at modelling the effects of the methane release to the atmosphere.
A large number of data sets related to physical and chemical processes connected
to the outburst and ascent of methane will be generated. All datasets will
be integrated in a geographically-related database that will be distributed
on the Internet.
The project proposes an integrated, multidisciplinary study, addressing
the following topics:
margin of this study, the project will generate important data for environmental
and climatic issues in the Black Sea region:
ORIGIN OF HIGH-INTENSITY METHANE SEEPS AND OUTBURSTS: as the destabilisation
of gas hydrates has been considered as a major source of submarine methane,
the relation between gas hydrate destabilisation and methane outbursts
will be investigated. In the project two sites where high-intensity
seeps occur will be studied, one shallow site that is located outside
the stability field of gas hydrates, another deep site that is located
within the gas hydrate stability field.
THE METHANE FLUX FROM THE SEAFLOOR, IN THE WATER COLUMN AND AT THE SEA
SURFACE TO THE ATMOSPHERE: the quantity of methane released at the seafloor
will be measured in two seep areas. The physical characteristics of
injected methane clouds will be analysed: bubble characteristics, concentration
of dissolved methane and transformation during vertical transport in
the water column and at the anoxic/oxic interface.
The chemical characteristics of the injected gasses will be determined
and the concentrations at several levels throughout the water column
and at the sea/atmosphere interface will be measured. Also the role
of the bacteria will be investigated and their role as a methane sink
will be quantified. The results will be combined to quantify the methane
losses and transformation during vertical transport and to quantify
the flux resulting from methane injections to the atmosphere.Physical
and chemical changes in the water mass caused by ascending methane clouds
will be quantified.
THE SIGNIFICANCE OF SUBMARINE OUTBURSTS AS A CAUSE OF ATMOSPHERIC CHANGES:
the changes in the oxidizing capacity of the atmosphere above the Black
Sea will be calculated in box models on basis of the established methane
flux from submarine high-intensity seeps at the sea surface.
gas release causes extreme eutrophication of the water mass. The boundary
between anoxic and oxic water layers oscillates between 150 m and 180
m below the sea surface. The maximum depth of the Black Sea being 2212
m, it represents the largest anoxic water mass on Earth. Measurements
suggest that the oxic-anoxic interface is shallowing, which has catastrophic
effects for fisheries, etc.
Black Sea is a key region for South European climate, the source of
South European rainfall. Changes in climate in the Black Sea region
have immediate effects on climate conditions in southern Europe.
global climate change is steered by pulses of increased concentration
of greenhouse gases, one of the most important natural gases is methane:
information already is known about methane in the Black Sea. Several studies
have been dealing with the methane content in the seawater. Methane fluxes
at the sea surface have been measured and evaluations of the methane release
have been made for several areas. Outbursts of methane at the seafloor have
been well documented. The presence of gas hydrates in the sub-bottom sediments
is becoming a popular topic for investigation: several on-going projects
or ready to start are dealing with the processes of destabilization of gas
hydrates and their effects on the methane content in the seawater.
is a powerful greenhouse gas, 25 times more efficient than carbon dioxide
at trapping heat but has a shorter residence time in the atmosphere
(10 years compared to 100 years for CO2).
release in large quantities to the atmosphere may cause a sudden warming
of the global climate and trigger rapid global climate change
of increased atmospheric methane levels has been found in ice cores
and ocean-bottom sediment cores coincident with periods of rapid climate
change, e.g. Late Palaeocene Thermal Maximum, etc
case of the LPTM, large amounts of methane -assumed to be derived from
massive destabilisation of marine hydrate deposits- were injected from
the seafloor into the ocean and the atmosphere, causing warming of ocean
waters and atmosphere, changes in the ocean currents and extinction
of many benthic species.
CRIMEA project will focus on the transfer of methane from the seafloor
through the water column and into the atmosphere from submarine high-intensity
methane seeps and outbursts in the Black Sea. In high-intensity seeps,
methane escapes as free gas in large volumes. Such seeps are more likely
to have a pronounced effect on atmosphere and climate than the "normal"
steady seeps where the larger part of the methane is dissolved and oxidised,
consumed by bacteria or fixed in seafloor carbonate crusts.
density, size and ascending velocity are much larger then in steady,
bubble curtains, or plumes (also flares), can reach up to 200 m high
in the water column or even reach the sea surface where the methane
may inflame. A "burning sea" is not unusual during thunderstorms
over the Black Sea.
methane outbursts emit methane directly from the ocean floor into the
deeper water (>200 m) the flares may not reach the sea surface but
the methane travelled through a large part of the water column before
the methane is dissolved, diluted and eventually oxidized and its contribution
to methane or carbon dioxide emission at the ocean-atmosphere interface
may be significant
INNOVATIVE ASPECTS OF THE PROJECT
It will attempt to quantify the influence on the atmospheric composition
of large outbursts of methane at the seafloor. Indeed, methane from
steady seafloor seeps is partly consumed by bacteria at the emanation
sites, and is further for a large part oxidized at the anoxic/oxic water
interface. Only the methane abruptly erupting at the seafloor and ascending
in plumes in the water column (which is well documented in the proposed
study areas) is able to reach in huge quantities the upper water layers
and the atmosphere. In the Black Sea enormous amounts of methane are
continuously injected into the water at several places. It would be
nearly impossible to perform this study in other areas where outbursts
are significant but occur episodically.
In the research for submarine sources of external methane destabilization
of gas hydrates is often considered the main methane source; it is believed
to be capable of rapidly liberating large amounts of methane. The CRIMEA
project will be able to test this hypothesis by:
- quantifying the real contribution of submarine methane outbursts to
changes in atmospheric composition, and
- studying the role of gas hydrates as a buffer for, or originator of
It builds an interactive and interdisciplinary program to define and
to quantify all the processes involved, from the origin of the methane
in the sub-bottom sediments to its release to the atmosphere:
- methane generation in the sea sediments, and particularly the role
of gas hydrate dissociation as a buffer for, or originator of methane
outbursting in high-energy events
- the physical, chemical and biological processes occurring at the venting
sites, in the water column and at density barriers (e.g. oxic/anoxic
- the methane emanation at the sea surface caused by methane outbursts
compared to other undisturbed areas.
- the influence of this contribution on the atmospheric composition.
To measure and model all involved processes the CRIMEA project makes
use of state-of-the-art technology and mathematical models from different
disciplines and for various applications, combined in an efficient work
adequately study and quantify the methane release from the seafloor and
its contribution to atmospheric methane emission, the project comprises
four main experimental components:
Characterization of methane sources and analysis of migration pathways.
The work to be done will be limited to selected venting areas and seeps,
relying further on the results of nationally funded on-going research
projects dealing with gas hydrate destabilisation and methane seepages;
Characterization and mapping of surface seeps. This component
is mainly based on geophysical techniques;
Characterization and quantification of fluids, gasses and microbiological
activity in the shallow subsurface, at the seafloor in high-intensity
active seeps. This component is mainly based on gas, water and sediment
sampling and analysis combined with remote and in-situ visualisation
Characterization of the physical, chemical and biological processes
related to the fate of methane in the water column. Particular attention
will be paid to the processes acting at the different interfaces: oxic/anoxic
and water/atmosphere. This component relies on in-situ physical and
chemical measurements, and water sampling and analysis.
experiments will be performed in two test areas: at the limit of the shelf
in the NW Ukrainian part of the Black Sea, at depths varying between 100
and 2000 m; in the abyssal plain of the Black Sea, at a water depth of
about 2000 m.
experimental work will be completed by modelling the physical and
chemical processes in the water column connected to methane ascent
in plumes, and by modelling the effects on the atmosphere
of methane release related to these outbursts.
PRESENTATION OF THE PROJECT'S COMPONENTS