ALBERT

Description: Recently, measurements of oxygen concentration in the ocean-one of the most classical parameters in chemical oceanography-are experiencing a revival. This is not surprising, given the key role of oxygen for assessing the status of the marine carbon cycle and feeling the pulse of the biological pump. The revival, however, has to a large extent been driven by the availability of robust optical oxygen sensors and their painstakingly thorough characterization. For autonomous observations, oxygen optodes are the sensors of choice: They are used abundantly on Biogeochemical-Argo floats, gliders and other autonomous oceanographic observation platforms. Still, data quality and accuracy are often suboptimal, in some part because sensor and data treatment are not always straightforward and/or sensor characteristics are not adequately taken into account. Here, we want to summarize the current knowledge about oxygen optodes, their working principle as well as their behavior with respect to oxygen, temperature, hydrostatic pressure, and response time. The focus will lie on the most widely used and accepted optodes made by Aanderaa and Sea-Bird. We revisit the essentials and caveats of in-situ in air calibration as well as of time response correction for profiling applications, and provide requirements for a successful field deployment. In addition, all required steps to post-correct oxygen optode data will be discussed. We hope this summary will serve as a comprehensive, yet concise reference to help people get started with oxygen observations, ensure successful sensor deployments and acquisition of highest quality data, and facilitate post-treatment of oxygen data. In the end, we hope that this will lead to more and higher-quality oxygen observations and help to advance our understanding of ocean biogeochemistry in a changing ocean.

Description: Over the past 200 years ~50% of the CO2 released to the atmosphere via the burning of fossil-fuels or changes in land-use (“anthropogenic carbon”) has dissolved in the oceans. This carbon sequestration by natural processes has drastically reduced the global warming effect of mankind’s CO2 emissions. However the dissolution of anthropogenic CO2 in the future ocean is likely to be reduced due to chemical changes associated with higher CO2 levels and, possibly, due to changes in ocean circulation associated with climate change. Critical scientific issues for prediction of future carbon sequestration and hence future atmospheric CO2 levels are the mechanisms underlying ocean CO2 uptake, the regions of the surface ocean that are responsible, and the depth range within the ocean in which the CO2 is being stored. This information is also critical to understanding the effects of CO2-induced ocean acidification.

Description: Meteor 68/3 Der dritte Fahrtabschnitt der 68. Meteor Expedition findet unter Fahrtleitung von Prof. Dr. Arne Körtzinger in der Zeit vom 12.07. bis 06.08.2006 statt Der Abschnitt steht als 2. Deutsche SOLAS-Expedition unter dem programmatischen Rahmen der internationalen „Surface Ocean Lower Atmosphere Study“.Sie bündelt ein breites Spektrum von biologischer, chemischer und physikalischer Ozeanographie sowie Atmosphärenchemie und ist regional auf den Küstenauftrieb vor Mauretanien fokussiert. Diese Region ist durch wichtige SOLAS-relevante Phänomene und Prozesse gekennzeichnet, zu denen atmosphärischer Staubeintrag aber vor allem Auftriebsphänome gehören, die für viele Komponenten (Eisen, Nährstoffe, CO2, flüchtige Halogenkohlenwasserstoffe) und Prozesse (Stickstoff-Fixierung, Ozean-Atmosphäre-Gasaustausch) eine zentrale Rolle spielen. Auftriebsgebiete in Regionen mit starkem Staubeintrag stellen gewissermaßen biogeochemische Reaktoren dar, die gleichzeitig durch vertikale (Makro- und Mikro-) Nährstoffeinträge aus der Atmosphäre und dem Mesopelagial angetrieben werden. Zugleich stellen sie Regionen dar, über die eine rasche Ventilation von unterhalb der Deckschicht produzierten klimarelevanten Spurengasen (CO2, Lachgas, Bromoform etc.) erfolgt. Die zu beobachtenden Ozean-Atmosphäre-Flussdichten liegen zum Teil um Größenordnungen über den im offenen oligotrophen Ozean vorgefundenen Verhältnissen.

Description: This work presents two new methods to estimate oceanic alkalinity (AT), dissolved inorganic carbon (CT), pH, and pCO2 from temperature, salinity, oxygen, and geolocation data. “CANYON-B” is a Bayesian neural network mapping that accurately reproduces GLODAPv2 bottle data and the biogeochemical relations contained therein. “CONTENT” combines and refines the four carbonate system variables to be consistent with carbonate chemistry. Both methods come with a robust uncertainty estimate that incorporates information from the local conditions. They are validated against independent GO-SHIP bottle and sensor data, and compare favorably to other state-of-the-art mapping methods. As “dynamic climatologies” they show comparable performance to classical climatologies on large scales but a much better representation on smaller scales (40–120 d, 500–1,500 km) compared to in situ data. The limits of these mappings are explored with pCO2 estimation in surface waters, i.e., at the edge of the domain with high intrinsic variability. In highly productive areas, there is a tendency for pCO2 overestimation due to decoupling of the O2 and C cycles by air-sea gas exchange, but global surface pCO2 estimates are unbiased compared to a monthly climatology. CANYON-B and CONTENT are highly useful as transfer functions between components of the ocean observing system (GO-SHIP repeat hydrography, BGC-Argo, underway observations) and permit the synergistic use of these highly complementary systems, both in spatial/temporal coverage and number of observations. Through easily and robotically-accessible observations they allow densification of more difficult-to-observe variables (e.g., 15 times denser AT and CT compared to direct measurements). At the same time, they give access to the complete carbonate system. This potential is demonstrated by an observation-based global analysis of the Revelle buffer factor, which shows a significant, high latitude-intensified increase between +0.1 and +0.4 units per decade. This shows the utility that such transfer functions with realistic uncertainty estimates provide to ocean biogeochemistry and global climate change research. In addition, CANYON-B provides robust and accurate estimates of nitrate, phosphate, and silicate. Matlab and R code are available at https://github.com/HCBScienceProducts/. Introduction

Description: The European Research Infrastructure Consortium “Integrated Carbon Observation System” (ICOS) aims at delivering high quality greenhouse gas (GHG) observations and derived data products (e.g., regional GHG-flux maps) for constraining the GHG balance on a European level, on a sustained long-term basis. The marine domain (ICOS-Oceans) currently consists of 11 Ship of Opportunity lines (SOOP – Ship of Opportunity Program) and 10 Fixed Ocean Stations (FOSs) spread across European waters, including the North Atlantic and Arctic Oceans and the Barents, North, Baltic, and Mediterranean Seas. The stations operate in a harmonized and standardized way based on community-proven protocols and methods for ocean GHG observations, improving operational conformity as well as quality control and assurance of the data. This enables the network to focus on long term research into the marine carbon cycle and the anthropogenic carbon sink, while preparing the network to include other GHG fluxes. ICOS data are processed on a near real-time basis and will be published on the ICOS Carbon Portal (CP), allowing monthly estimates of CO2 air-sea exchange to be quantified for European waters. ICOS establishes transparent operational data management routines following the FAIR (Findable, Accessible, Interoperable, and Reusable) guiding principles allowing amongst others reproducibility, interoperability, and traceability. The ICOS-Oceans network is actively integrating with the atmospheric (e.g., improved atmospheric measurements onboard SOOP lines) and ecosystem (e.g., oceanic direct gas flux measurements) domains of ICOS, and utilizes techniques developed by the ICOS Central Facilities and the CP. There is a strong interaction with the international ocean carbon cycle community to enhance interoperability and harmonize data flow. The future vision of ICOS-Oceans includes ship-based ocean survey sections to obtain a three-dimensional understanding of marine carbon cycle processes and optimize the existing network design.