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| Titel |
Characterising marine and lacustrine methane macro-seeps in 14 steps |
| VerfasserIn |
Martin Hovland, Christine Fichler |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046858
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| Zusammenfassung |
| The two main factors characterising marine and lacustrine methane macro-seeps are 1)
ebullition through holes in the sea- or lake-bed, and, 2) hydroacoustic “flares” in the water
column. After having reviewed multi-year, multi-scale, and multi-discipline results from
several methane macro-seeps in the North Sea and elsewhere, a series of up to 12 additional
factors of such seeps have been identified. This means that it may be possible to provide a
quantitative number (“sum of factors”) by which to characterise each methane-macro seep
location.
The additional identified factors that characterise methane macro-seeps are as follows:
3) high CH4-levels in water and pore-water, 4) visual and chemical aureole, 5) chemical and
temperature anomalies, 6) topographical effects, 7) methane derived authigenic carbonate,
MDAC, development, 8) bacterial mats and blooms, 9) upwelling seawater, 10) down-welling
seawater into sub-surface conduits, 11) sea-surface effects, 12) slicks and nutrients on surface
/birds feeding, 13) attraction of fish and other macro-fauna, 14) methane anomalies in lower
atmosphere. With such a list of factors at hand, it should not only be possible to quantify
and rank the seeps, but also to provide a methodology or guideline on how best to
study such seeps in a comprehensive manner. The attached table suggests how
one seep location in the North Sea (Tommeliten) can be quantified with a “sum”.
The higher this sum, the more influential and significant the seep is expected to
be.
The total Sum for this methane macro-seep is found by adding all the scores, i.e., the
Tommeliten A seep sum is 24. As more information from macro-seeps is gained in
future surveys, it is expected that new observations will add new factors, one of
which is expected to be magnetic susceptibility. Thus, the table presented here, just
represents a methodological suggestion for how seeps can be compared in a quantifiable
manner.
# Factor Score
1 Ebullition 2
2 Flare 3
3 CH4 anomaly 3
4 Aureole 2
5 Temp/Chem 1
6 Topography 1
7 MDAC 2
8 Bact. mats 3
9 Upwelling 1
10 Downwelling 1
11 Sea-Surf. 1
12 Nutrients 2
13 Fish attract. 1
14 Atmosph CH4 1
Total sum: 24 |
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