Continuous measurement of methane and carbon dioxide concentrations in surface waters based on off-axis integrated cavity output spectroscopy (ICOS).

Gülzow, W., Rehder, Gregor, Schneider von Deimling, Jens, Sadkowiak, B. and Schneider, B, (2010) Continuous measurement of methane and carbon dioxide concentrations in surface waters based on off-axis integrated cavity output spectroscopy (ICOS). [Talk] In: AGU Fall Meeting 2010. , 13.-17.12.2010, San Francisco, USA .

Full text not available from this repository.

Abstract

Though systems to assess the sea surface concentrations of climate-relevant trace gases were first designed three decades ago, only for carbon dioxide the technology has advanced far enough to allow quasi non-maintained data acquisition based on ships of opportunity. One of the reasons for this is the fact that until now, only for carbon dioxide the concentrations in surface waters are high enough to allow the use of non gas-consuming, IR-spectroscopy-based detection of the gas, usually provided by a LICOR gas detector. This causes problems to estimate the marine fluxes of other important trace gases such as methane or nitrous oxide, which are usually strongly bound to coastal and estuarine zones, and thus would require long-term, spatio-temporal data acquisition for a robust marine source assessment. Here, we present a new system which allows to measure methane and carbon dioxide in surface waters autonomously and continuously using a non-gas consuming optical detection system. The analytical setup consists of a CH4/CO2- Analyzer (MCA; Los Gatos Research) joint with a bubble-type equilibration system. The analyzer uses off-axis integrated cavity output spectroscopy (ICOS) which combines two highly specific band lasers with a set of strongly reflective mirrors to obtain an effective laser path length of several kilometers. While a first system was installed in November 2009 on the cargo ship Finnmaid (Finnpartner) that commutes regularly between Travemünde (Germany) and Helsinki (Finnland) in the Baltic Sea, a 2nd system was build to be used on board of research vessels and successfully monitored the gas concentrations along the ship track during a 3,5 week long research cruise of RV Maria S. Merian (MSM16/1) in the Baltic Sea in August, 2010. Very low post-bloom surface pCO2 values and distinct patterns of surface methane concentrations pointing to local sources were amongst the results of the surface survey. During the expedition, the system was also linked to the outlet of a pump-CTD system which was lowered into the euxinic, methane-enriched part of the water column, revealing a distinct effect of H2S concentrations on the water vapor band, which needs to be assessed before the system is used for this kind of investigations.

Document Type: Conference or Workshop Item (Talk)
Date Deposited: 25 Sep 2012 10:17
Last Modified: 02 Nov 2016 09:30
URI: http://oceanrep.geomar.de/id/eprint/15108

Actions (login required)

View Item View Item