Steven van Heuven

University of Groningen

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Mario Hoppema

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Are Olsen

University of Bergen

Robert M. Key

Princeton University

Toste Tanhua

GEOMAR Helmholtz Centre for Ocean Research Kiel

A. Velo

Instituto de Investigacións Mariñas

Siv K. Lauvset

NORCE Norwegian Research Centre

H. J. W. de Baar

Ecosystem Sciences

Rik Wanninkhof

NOAA Atlantic Oceanographic and Meteorological Laboratories

Fı́z F. Pérez

Instituto de Investigacións Mariñas

Carsten Schirnick

GEOMAR Helmholtz Centre for Ocean Research Kiel

Cooperative Institutions

Centre National de la Recherche Scientifique

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Royal Netherlands Institute for Sea Research

Woods Hole Oceanographic Institution

National Oceanic and Atmospheric Administration

Utrecht University

Institut de Recherche pour le Développement

GEOMAR Helmholtz Centre for Ocean Research Kiel

National Oceanography Centre

Lamont-Doherty Earth Observatory

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Arctic Ocean CO2 uptake: an improved multi-year estimate of the air–sea CO2 flux incorporating chlorophyll-a concentrations

Sayaka Yasunaka Eko Siswanto Are Olsen Mario Hoppema Eiji Watanabe

Abstract. We estimated monthly air–sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of 60° N from 1997 to 2014, after mapping partial pressure of CO2 in the surface water (pCO2w) using a self-organizing map (SOM) technique incorporating chlorophyll-a concentration (Chl-a), sea surface temperature, sea surface salinity, sea ice concentration, atmospheric CO2 mixing ratio, and geographical position. The overall relationship between pCO2w and Chl-a is negative in most regions when Chl-a ≤ 1 mg m−3, whereas there is no significant relationship when Chl-a > 1 mg m−3. In the Kara Sea and the East Siberian Sea and the Bering Strait, however, the relationship is typically positive in summer. The addition of Chl-a as a parameter in the SOM process enabled us to improve the estimate of pCO2w via better representation of its decline in spring, which resulted from biologically mediated pCO2w reduction. Mainly as a result of the inclusion of Chl-a, the uncertainty in the CO2 flux estimate was reduced, and a net annual Arctic Ocean CO2 uptake of 180 ± 130 TgC y−1 was determined to be significant.

10.5194/bg-2017-320

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Quantifying functional consequences of habitat degradation on a Caribbean coral reef

Biogeosciences (2021)

Alice E. Webb Didier M. de Bakker Karline Soetaert Tamara da Costa Steven van Heuven

Abstract. Coral reefs are declining worldwide. The abundance of corals has decreased alongside a rise of filter feeders, turf, and algae in response to intensifying human pressures. This shift in prevalence of functional groups alters the biogeochemical processes in tropical water ecosystems, thereby influencing reef functioning. An urgent challenge is to understand the functional consequences of these shifts to develop suitable management strategies that aim at preserving the biological functions of reefs. Here, we quantify biogeochemical processes supporting key reef functions (i.e. net community calcification (NCC) and production (NCP) and nutrient recycling) in situ for five different benthic assemblages currently dominating shallow degraded Caribbean reef habitats. To this end, a transparent custom-made enclosure was placed over communities dominated by either one of five functional groups – coral, turf and macroalgae, bioeroding sponges, cyanobacterial mats, or sand – to determine chemical fluxes between these communities and the overlying water, during both day and night. To account for the simultaneous influence that distinct biogeochemical processes have on measured variables, the rates were then derived by solving a model consisting of differential equations describing the contribution of each process to the measured chemical fluxes. Inferred rates were low compared to those known for reef flats worldwide. Reduced accretion potential was recorded, with negative or very modest net community calcification rates for all communities. Net production during the day was also low, suggesting limited accumulation of biomass through photosynthesis and remineralisation of organic matter at night was relatively high in comparison, resulting in net heterotrophy over the survey period for most communities. Estimated recycling processes (i.e. nitrification and denitrification) were high but did not fully counterbalance nutrient release from aerobic mineralisation, rendering all substrates sources of nitrogen. Results suggest similar directions and magnitudes of key biogeochemical processes of distinct communities on this shallow Curaçaoan reef. We infer that the amount and type of organic matter released by abundant algal turfs and cyanobacterial mats on this reef likely enhances heterotroph activity and stimulates the proliferation of less diverse copiotrophic microbial populations, rendering the studied reef net heterotrophic and drawing the biogeochemical “behaviour” of distinct communities closer to each other.

Biogeochemical Cycle

10.5194/bg-18-6501-2021

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Increasing carbon inventory of the intermediate layers of the Arctic Ocean

Journal of Geophysical Research Oceans (2014)

Ylva Ericson Adam Ulfsbo Steven van Heuven Gerhard Kattner Leif G. Anderson

Concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA), nutrients, and oxygen in subsurface waters of the central Arctic Ocean have been investigated for conceivable time trends over the last two decades. Data from six cruises (1991–2011) that cover the Nansen, Amundsen, and Makarov Basins were included in this analysis. In waters deeper than 2000 m, no statistically significant trend could be observed for DIC, TA, phosphate, or nitrate, but a small rate of increase in apparent oxygen utilization (AOU) was noticeable. For the individual stations, differences in concentration of each property were computed between the mean concentrations in the Arctic Atlantic Water (AAW) or the upper Polar Deep Water (uPDW), i.e., between about 150 and 1400 m depth, and in the deep water (assumed invariable over time). In these shallower water layers, we observe significant above-zero time trends for DIC, in the range of 0.6–0.9 μmol kg−1 yr−1 (for AAW) and 0.4–0.6 µmol kg−1 yr−1 (for uPDW). No time trend in nutrients could be observed, indicating no change in the rate of organic matter mineralization within this depth range. Consequently, the buildup of DIC is attributed to increasing concentrations of anthropogenic carbon in the waters flowing into these depth layers of the Arctic Ocean. The resulting rate of increase of the column inventory of anthropogenic CO2 is estimated to be between 0.6 and 0.9 mol C m−2 yr−1, with distinct differences between basins.

Alkalinity

Total inorganic carbon

Carbon fibers

10.1002/2013jc009514

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Citations (18)

CO2, nutrients, manganese and iron in the upper ocean: the Atlantic sector of the Southern Ocean

Mario Hoppema Rob Middag Steven van Heuven

Geotraces

Ocean chemistry

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CARINA TCO2 data in the Atlantic Ocean

Earth system science data (2010)

Denis Pierrot Peter J. Brown Steven van Heuven Toste Tanhua Ute Schuster

Abstract. Water column data of carbon and carbon-relevant hydrographic and hydrochemical parameters from 188 cruises in the Arctic Mediterranean Seas, Atlantic and Southern Ocean have been retrieved and merged in a new data base: the CARINA (CARbon IN the Atlantic) Project. These data have gone through rigorous quality control (QC) procedures so as to improve the quality and consistency of the data as much as possible. Secondary quality control, which involved objective study of data in order to quantify systematic differences in the reported values, was performed for the pertinent parameters in the CARINA data base. Systematic biases in the data have been tentatively corrected in the data products. The products are three merged data files with measured, adjusted and interpolated data of all cruises for each of the three CARINA regions (Arctic Mediterranean Seas, Atlantic and Southern Ocean). Ninety-eight cruises were conducted in the "Atlantic" defined as the region south of the Greenland-Iceland-Scotland Ridge and north of about 30° S. Here we report the details of the secondary QC which was done on the total dissolved inorganic carbon (TCO2) data and the adjustments that were applied to yield the final data product in the Atlantic. Procedures of quality control – including crossover analysis between stations and inversion analysis of all crossover data – are briefly described. Adjustments were applied to TCO2 measurements for 17 of the cruises in the Atlantic Ocean region. With these adjustments, the CARINA data base is consistent both internally as well as with GLODAP data, an oceanographic data set based on the WOCE Hydrographic Program in the 1990s, and is now suitable for accurate assessments of, for example, regional oceanic carbon inventories, uptake rates and model validation.

10.5194/essd-2-177-2010

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The oceanic sink for anthropogenic CO ₂ from 1994 to 2007

Science (2019)

Nicolas Gruber Dominic Clement Brendan R. Carter Richard A. Feely Steven van Heuven

We quantify the oceanic sink for anthropogenic carbon dioxide (CO2) over the period 1994 to 2007 by using observations from the global repeat hydrography program and contrasting them to observations from the 1990s. Using a linear regression-based method, we find a global increase in the anthropogenic CO2 inventory of 34 ± 4 petagrams of carbon (Pg C) between 1994 and 2007. This is equivalent to an average uptake rate of 2.6 ± 0.3 Pg C year-1 and represents 31 ± 4% of the global anthropogenic CO2 emissions over this period. Although this global ocean sink estimate is consistent with the expectation of the ocean uptake having increased in proportion to the rise in atmospheric CO2, substantial regional differences in storage rate are found, likely owing to climate variability-driven changes in ocean circulation.

Sink (geography)

10.1126/science.aau5153

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Rapid invasion of anthropogenic CO₂into the deep circulation of the Weddell Gyre

Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences (2014)

Steven van Heuven Mario Hoppema Elizabeth M. Jones H. J. W. de Baar

Data are presented for total carbon dioxide (TCO2), oxygen and nutrients from 14 cruises covering two repeat sections across the Weddell Gyre, from 1973 to 2010. Assessments of the rate of increase in anthropogenic CO2 (Cant) are made at three locations. Along the Prime Meridian, TCO2 is observed to steadily increase in the bottom water. Accompanying changes in silicate, nitrate and oxygen confirm the non-steady state of the Weddell circulation. The rate of increase in TCO2 of +0.12±0.05 μmol kg(-1) yr(-1) therefore poses an upper limit to the rate of increase in Cant. By contrast, the bottom water located in the central Weddell Sea exhibits no significant increase in TCO2, suggesting that this water is less well ventilated at the southern margins of the Weddell Sea. At the tip of the Antarctic Peninsula (i.e. the formation region of the bottom water found at the Prime Meridian), the high rate of increase in TCO2 over time observed at the lowest temperatures suggests that nearly full equilibration occurs with the anthropogenic CO2 of the atmosphere. This observation constitutes rare evidence for the possibility that ice cover is not a major impediment for uptake of Cant in this prominent deep water formation region.

Antarctic Bottom Water

Circumpolar deep water

10.1098/rsta.2013.0056

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Slowing down of deep and bottom water ventilation and anthropogenic carbon storage in the Weddell Sea

Oliver Huhn Monika Rhein Mario Hoppema Steven van Heuven

Antarctic Bottom Water

Water storage

Carbon fibers

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Ocean Biochemical Cycling and Trace Elements

Encyclopedia of earth sciences series/Encyclopedia of earth sciences (2017)

H. J. W. de Baar Steven van Heuven Rob Middag

Cycling

TRACE (psycholinguistics)

10.1007/978-3-319-39193-9_356-1

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Overview of the Nordic Seas CARINA data and salinity measurements

Are Olsen Robert M. Key Emil Jeansson Eva Falck Jón Ólafsson

Abstract. Water column data of carbon and carbon relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruises in the Arctic, Atlantic, and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon IN the Atlantic). The data have been subject to rigorous quality control (QC) in order to ensure highest possible quality and consistency. The data for most of the parameters included were examined in order to quantify systematic biases in the reported values, i.e. secondary quality control. Significant biases have been corrected for in the data products, i.e. the three merged files with measured, calculated and interpolated values for each of the three CARINA regions; the Arctic Mediterranean Seas (AMS), the Atlantic (ATL) and the Southern Ocean (SO). With the adjustments the CARINA database is consistent both internally as well as with GLODAP (Key et al., 2004) and is suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation. The Arctic Mediterranean Seas includes the Arctic Ocean and the Nordic Seas, and the quality control was carried out separately in these two areas. This contribution provides an overview of the CARINA data from the Nordic Seas and summarises the findings of the QC of the salinity data. One cruise had salinity data that were of questionable quality, and these have been removed from the data product. An evaluation of the consistency of the quality controlled salinity data suggests that they are consistent to at least 0.05.

10.5194/essdd-2-1-2009

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Citations (13)