RV Sonne Cruise Report SO196: SUMSUN 2008, Suva – Guam – Okinawa Trough – Manila, February 19 - March 26, 2008.

Rehder, Gregor and Schneider von Deimling, Jens, eds. (2008) RV Sonne Cruise Report SO196: SUMSUN 2008, Suva – Guam – Okinawa Trough – Manila, February 19 - March 26, 2008. . , Warnemünde, 289 pp.

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1.1 SUMSUN Objective
In the frame of the agreement of Kyoto and beyond, the directives of emission trading promoted
by the EU, as well as the research of deposition/dumping of CO2 especially supported by the
U.S.A and Japan, the discharge of CO2 into the ocean is considered as a possibility to reduce
CO2 emission into the atmosphere. The injection of liquid CO2 in midwater or at the seafloor,
which are the major scenarios discussed in the IPCC 2005 special report on CCS for marine
carbon storage, became less likely due to the increasing awareness of ocean acidification. At
the same time, it has been promoted that storage in deep marine sediments might be the safest
option for carbon storage, as density gradients favour migration into the sediment and the
potential to form CO2 hydrates acts as an additional barrier for re-entering of the CO2 into the
ocean/atmosphere system.
The expedition 196 of RV SONNE is the central field campaign of the Project SUMSUN
(“StUdien zur Marinen CO2-Sequestrierung durch Untersuchung natürlicher hydrothermaler
CO2-Austritte im Nördlichen Westpazifik”. The project aims to investigate some of the few
known hydrothermal locations where liquid CO2 is stored in the upper sediment or is escaping
from the seafloor in forms of droplets with CO2 as the main component. Though the geological
and hydrothermal framework resulting in the separation of a CO2-dominated volatile phase is an
interesting topic on its own, this is not in the main focus of the project. SUMSUN aims to
investigate the interaction of liquid CO2 with the seafloor and the water column and potential
impact on seafloor geochemistry and biology. The rationale is to characterize a natural
analogue for proposed scenarios of CO2 deposition in the ocean.

Three of the four locations known today where liquid CO2 generated by hydrothermal activity
interacts with the seafloor and/or emanates into the water column, are located in the Okinawa
Trough. The processes in the vicinity of CO2 injection in case of direct injection or leakage from
subsedimentary storage are poorly defined, mainly because of the complex phase relations
between liquid CO2, sea water, and CO2 hydrate. The ascent of liquid CO2 drops is also subject
to ensemble relations which are not reproducible in the laboratory. The effects of increased CO2
concentration on marine organisms are poorly investigated, in particular thresholds and
adaption ability on longer timescales. Geochemical interactions are crucial because of the pHand
pCO2-sensitivity of a variety of important diagenetic reactions. The overarching objective of
SO196 is thus to investigate the CO2-rich vent sites in the Okinawa Trough to get insights and
draw conclusions for the potential effects involved in the purposeful storage of CO2 at the

Document Type: Report (Cruise Report)
Keywords: SO196 ; RV SONNE ; SUMSUN ; Okinawa Trough
Open Access Journal?: Yes
Date Deposited: 04 Apr 2013 09:37
Last Modified: 04 Apr 2013 09:37
URI: http://oceanrep.geomar.de/id/eprint/20848

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