The Benguela Upwelling System (BUS) is the most productive of all eastern boundary upwelling ecos... more The Benguela Upwelling System (BUS) is the most productive of all eastern boundary upwelling ecosystems and it hosts a well-developed oxygen minimum zone. As such, the BUS is a potential hotspot for production of N 2 O, a potent greenhouse gas derived from microbially driven decay of sinking organic matter. Yet, the extent at which near-surface waters emit N 2 O to the atmosphere in the BUS is highly uncertain. Here we present the first high-resolution surface measurements of N 2 O across the northern part of the BUS (nBUS). We found strong gradients with a threefold increase in N 2 O concentrations near the coast as compared with open ocean waters. Our observations show enhanced sea-to-air fluxes of N 2 O (up to 1.67 nmol m −2 s −1) in association with local upwelling cells. Based on our data we suggest that the nBUS can account for 13% of the total coastal upwelling source of N 2 O to the atmosphere. Plain Language Summary Nitrous oxide (N 2 O), commonly known as "laughing gas," is a potent greenhouse gas that contributes both to Earth's warming and to the depletion of ozone in the stratosphere. Typically, N 2 O is produced in the water column as a result of microbial decay of organic matter (under low oxygen conditions) and then it is transferred to the atmosphere at the air-sea interface. Hence, high productive regions associated with low oxygen waters could create "hotspots" for N 2 O production. Yet, emission estimates might have underestimated the potential of coastal regions due to data sparcity. We focus on the northern Benguela region, which is the most productive of four major coastal upwelling ecosystems. Here we aim to answer: what is the large-scale distribution and variability of air-sea fluxes of N 2 O? What is the impact of small-scale oceanographic features in N 2 O variability? and Do regional emissions of N 2 O need to be revisited? Based on the analysis of continuous highly resolved measurements, we suggest that the share of this region to the total N 2 O emitted by the global ocean is higher than previously thought. Considering that this region represents only 0.06% of the ocean surface, we argue that the marine budget of this gas might need revision. Eastern Boundary Upwelling Systems (EBUS) include some of the most productive regions of the ocean, accounting for about 11% of the global new production (Chavez & Toggweiler, 1995). The high productivity RESEARCH LETTER
Direct dimethyl sulfide (DMS) flux measurements using eddy covariance have shown a suppression of... more Direct dimethyl sulfide (DMS) flux measurements using eddy covariance have shown a suppression of gas transfer at medium to high wind speed. However, not all eddy covariance measurements show evidence of this suppression. Processes, such as wave-wind interaction and surfactants, have been postulated to cause this suppression. We measured DMS and carbon dioxide eddy covariance fluxes during the Asian summer monsoon in the western tropical Indian Ocean (July and August 2014). Both fluxes and their respective gas transfer velocities show signs of a gas transfer suppression above 10 m/s. Using a wind-wave interaction, we describe a flow separation process that could be responsible for a suppression of gas transfer. As a result we provide a Reynolds number-based parameterization, which states the likelihood of a gas transfer suppression for this cruise and previously published gas transfer data. Additionally, we compute the difference in the gas transfer velocities of DMS and CO 2 to estimate the bubble-mediated gas transfer using a hybrid model with three whitecap parameterizations.
The tropical Atlantic exerts a major influence in climate variability through strong air-sea inte... more The tropical Atlantic exerts a major influence in climate variability through strong air-sea interactions. Within this region, the eastern side of the equatorial band is characterized by strong seasonality, whereby the most prominent feature is the annual development of the Atlantic cold tongue (ACT). This band of low sea surface temperatures (22-238C) is typically associated with upwelling-driven enhancement of surface nutrient concentrations and primary production. Based on a detailed investigation of the distribution and sea-to-air fluxes of N 2 O in the eastern equatorial Atlantic (EEA), we show that the onset and seasonal development of the ACT can be clearly observed in surface N 2 O concentrations, which increase progressively as the cooling in the equatorial region proceeds during spring-summer. We observed a strong influence of the surface currents of the EEA on the N 2 O distribution, which allowed identifying ''high'' and ''low'' concentration regimes that were, in turn, spatially delimited by the extent of the warm eastwardflowing North Equatorial Countercurrent and the cold westward-flowing South Equatorial Current. Estimated sea-to-air fluxes of N 2 O from the ACT (mean 5.18 6 2.59 lmol m 22 d 21) suggest that in May-July 2011 this cold-water band doubled the N 2 O efflux to the atmosphere with respect to the adjacent regions, highlighting its relevance for marine tropical emissions of N 2 O.
Oceans are a net source of molecular hydrogen (H<sub>2</sub>) to the atmosphere. The ... more Oceans are a net source of molecular hydrogen (H<sub>2</sub>) to the atmosphere. The production of marine H<sub>2</sub> is assumed to be mainly biological by N<sub>2</sub> fixation, but photochemical pathways are also discussed. We present measurements of mole fraction and isotopic composition of dissolved and atmospheric H<sub>2</sub> from the southern and northern Atlantic between 2008 and 2010. In total almost 400 samples were taken during five cruises along a transect between Punta Arenas (Chile) and Bremerhaven (Germany), as well as at the coast of Mauretania. <br><br> The isotopic source signatures of dissolved H<sub>2</sub> extracted from surface water are highly deuterium-depleted and correlate negatively with temperature, showing δD values of (−629 ± 54) ‰ for water temperatures at (27 ± 3) °C and (−249 ± 88) ‰ below (19 ± 1) °C. The results for warmer water masses are consiste...
Accurate assessment of anthropogenic carbon dioxide (CO<sub>2</sub>) emissions and th... more Accurate assessment of anthropogenic carbon dioxide (CO<sub>2</sub>) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates as well as consistency within and among components, alongside methodology and data limitations. CO<sub>2</sub> emissions from fossil fuels and industry (<i>E</i><sub>FF</sub>) are based on energy statistics and cement production data, while emissions from land-use change…
Due to their high biological productivity coastal upwelling regions are important for biogeochemi... more Due to their high biological productivity coastal upwelling regions are important for biogeochemical cycles in the ocean and for fisheries. Upwelled water is not only enriched in nutrients but also supersaturated with respect to atmospheric CO 2 and N 2 O and undersaturated for O 2. We present a novel approach to estimate carbon based net community production (NCP) using surface ocean data for CO 2 , O 2 and N 2 O from three cruises to the Mauritanian upwelling region (Northwest Africa) that were conducted in different seasons. Through combination of the saturation patterns of CO 2 , O 2 and N 2 O effects of air-sea gas exchange and NCP could be separated. NCP values ranges from 0.6 ± 0.1 g C m −2 d −1 during times of weak upwelling to 1.6 ± 0.4 g C m −2 d −1 during strong upwelling. The estimated NCP values show a strong relationship with a wind derived upwelling index, which was used to estimate annual NCP.
Although hydrogen (H2) is considered as one of the most important future energy carriers, little ... more Although hydrogen (H2) is considered as one of the most important future energy carriers, little is known about the global biogeochemical cycle of this trace gas (Rhee et al. 2006). In order to assess the potential impact of expected increasing H2 concentrations to the atmosphere a fundamental understanding of the global H2 cycle is indispensable (Tromp et al. 2003, Warwick et al. 2004). Oceans are one source of atmospheric H2, produced by biological processes such as fermentation and N2-fixation and abiotic photochemical processes (Punshon and Moore 2008 and references herein). Further information can be obtained by studying the isotope composition of H2. However, the isotopic ratio of oceanic released H2 is unknown and has so far only been estimated from thermodynamic equilibrium. We investigated the atmospheric D/H isotopic ratio of H2 in the Atlantic Ocean. First results of atmospheric H2 isotope ratios from the West African coast of Mauritania and from a meridional transect over the Atlantic Ocean will be presented. Samples were taken onboard the German research vessel "Poseidon" in February 2007 associated to SOPRAN and during the cruise Ant XXIV-4 with the German research vessel "Polarstern" in April 2008 between Punta Arenas (Chile) and Bremerhaven (Germany).
Accurate assessment of anthropogenic carbon dioxide (CO 2) emissions and their redistribution amo... more Accurate assessment of anthropogenic carbon dioxide (CO 2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere-the "global carbon budget"-is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. CO 2 emissions from fossil fuels and industry (E FF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (E LUC), mainly deforestation, are based on land-cover change data and bookkeeping models. The global atmospheric CO 2 concentration is measured directly and its rate of growth (G ATM) is computed from the annual changes in concentration. The ocean CO 2 sink (S OCEAN) and terrestrial CO 2 sink (S LAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (B IM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2007-2016), E FF was 9.4 ± 0.
As a response to public demand for a welldocumented, quality controlled, publically available, gl... more As a response to public demand for a welldocumented, quality controlled, publically available, global surface ocean carbon dioxide (CO 2) data set, the international marine carbon science community developed the Surface Ocean CO 2 Atlas (SOCAT). The first SOCAT product is a collection of 6.3 million quality controlled surface CO 2 data from the global oceans and coastal seas, spanning four decades (1968-2007). The SOCAT gridded data presented here is the second data product to come from the SOCAT project. Recognizing that some groups may have trouble working with millions of measurements, the SOCAT gridded product was generated to provide a robust, regularly spaced CO 2 fugacity (f CO 2) product with minimal spatial and temporal interpolation, which should be easier to work with for many applications. Gridded SOCAT is rich with information that has not been fully explored yet (e.g., regional differences in the seasonal cycles), but also contains biases and limitations that the user needs to recognize and address (e.g., local influences on values in some coastal regions).
The oceans are a major sink for atmospheric carbon dioxide (CO 2). Historically, observations hav... more The oceans are a major sink for atmospheric carbon dioxide (CO 2). Historically, observations have been too sparse to allow accurate tracking of changes in rates of CO 2 uptake over ocean basins, so little is known about how these vary. Here, we show observations indicating substantial variability in the CO 2 uptake by the North Atlantic on time scales of a few years. Further, we use measurements from a coordinated network of instrumented commercial ships to define the annual flux into the North Atlantic, for the year 2005, to a precision of about 10%. This approach offers the prospect of accurately monitoring the changing ocean CO 2 sink for those ocean basins that are well covered by shipping routes.
A new system for continuous, highly-resolved oceanic and atmospheric measurements of N 2 O, CO an... more A new system for continuous, highly-resolved oceanic and atmospheric measurements of N 2 O, CO and CO 2 is described. The system is based upon off-axis integrated cavity output spectroscopy (OA-ICOS) and a non-dispersive infrared analyzer (NDIR) both coupled to a Weiss-type equilibrator. Performance of the combined setup was evaluated by testing its precision, accuracy, long-term stability, linearity and response time. Furthermore, the setup was tested during two oceanographic campaigns in the equatorial Atlantic Ocean in order to explore its potential for autonomous deployment onboard voluntary observing ships (VOS). Improved equilibrator response times for N 2 O (2.5 min) and CO (45 min) were achieved in comparison to response times from similar
The role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the ... more The role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the flux strengths between the ocean and the atmosphere can be quantified by measuring the fugacity of CO 2 (ƒCO 2) as well as the dissolved inorganic carbon (DIC) concentration and its isotopic composition in surface seawater. In this work, the potential of continuous wave cavity ringdown spectroscopy (cw-CRDS) for autonomous underway measurements of ƒCO 2 and the stable carbon isotope ratio of DIC [δ 13 C(DIC)] is explored. For the first time, by using a conventional air-sea equilibrator setup, both quantities were continuously and simultaneously recorded during a field deployment on two research cruises following meridional transects across the Atlantic Ocean (Bremerhaven, Germany-Punta Arenas, Chile). Data are compared against reference measurements by an established underway CO 2 monitoring system and isotope ratio mass spectrometric analysis of individual water samples. Agreement within ΔƒCO 2 = 0.35 μatm for atmospheric and ΔƒCO 2 = 2.5 μatm and Δδ 13 C(DIC) = 0.33‰ for seawater measurements have been achieved. Whereas "calibration-free" ƒCO 2 monitoring is feasible, the measurement of accurate isotope ratios relies on running reference standards on a daily basis. Overall, the installed CRDS/equilibrator system was shown to be capable of reliable online monitoring of ƒCO 2 , equilibrium δ 13 C(CO 2), δ 13 C(DIC), and pO 2 aboard moving research vessels, thus making possible corresponding measurements with high spatial and temporal resolution.
Gross photosynthetic O 2 production (GOP) rates in the subpolar North Atlantic Ocean were estimat... more Gross photosynthetic O 2 production (GOP) rates in the subpolar North Atlantic Ocean were estimated using the measured isotopic composition of dissolved oxygen in the surface layer on samples collected on nine transits of a container ship between Great Britain and Canada during March 2007 to June 2008. The mean basin-wide GOP rate of 226 AE 48 mmol O 2 m À2 d À1 during summer was double the winter rate of 107 AE 41 mmol O 2 m À2 d À1. Converting these GOP rates to equivalent 14 C-based PP (14 C-PP eqv) yielded rates of 1005 AE 216 and 476 AE 183 mg C m À2 d À1 in summer and winter, respectively, that generally agreed well with previous 14 C-based PP estimates in the region. The 14 C-PP eqv estimates were 1-1.6Â concurrent satellite-based PP estimates along the cruise track. A net community production rate (NCP) of 87 AE 12 mmol O 2 m À2 d À1 (62 AE 9 mmol C m À2 d À1) and NCP/GOP of 0.35 AE 0.06 in the mixed layer was estimated from O 2 /Ar and 17 D measurements (61 N 26 W) during spring bloom conditions in May 2008. Contrastingly, a much lower long-term annual mean NCP or organic carbon export rate of 2.8 AE 2.7 mol C m À2 yr À1 (8 AE 7 mmol C m À2 d À1) and NCP/GOP of 0.07 AE 0.06 at the winter mixed layer depth was estimated from 15 years of surface O 2 data in the subpolar N. Atlantic collected during the CARINA program.
Deep Sea Research Part II: Topical Studies in Oceanography, 2009
Corrigendum to Climatological mean and decadal change in surface ocean pCO 2 , and net seaair C... more Corrigendum to Climatological mean and decadal change in surface ocean pCO 2 , and net seaair CO 2 flux over the global oceans [Deep Sea Res. II 56 (2009) 554577] Deep Sea Research Part I: Oceanographic Research Papers, Volume 56, Issue 11, November 2009, Pages ...
Deep Sea Research Part I: Oceanographic Research Papers, 2009
Corrigendum to ''Climatological mean and decadal change in surface ocean pCO 2 , and net sea-air ... more Corrigendum to ''Climatological mean and decadal change in surface ocean pCO 2 , and net sea-air CO 2 flux over the global oceans'' [Deep Sea Res. II 56 (2009) 554-577]
Here we present an equation for the estimation of nitrate in surface waters of the North Atlantic... more Here we present an equation for the estimation of nitrate in surface waters of the North Atlantic Ocean (40 • N to 52 • N, 10 • W to 60 • W). The equation was derived by multiple linear regression (MLR) from nitrate, sea surface temperature (SST) observational data and model mixed layer depth (MLD) data. The observational data were taken from merchant vessels that have crossed the North Atlantic on a regular basis in 2002/2003 and from 2005 to the present. It is important to find a robust and realistic estimate of MLD because the deepening of the mixed layer is crucial for nitrate supply to the surface. We compared model data from two models (FOAM and Mercator) with MLD derived from float data (using various criteria). The Mercator model gives a MLD estimate that is close to the MLD derived from floats. MLR was established using SST, MLD from Mercator, time and latitude as predictors. Additionally a neural network was trained with the same dataset and the results were validated against both model data as a "ground truth" and an independent observational dataset. This validation produced RMS errors of the same order for MLR and the neural network approach. We conclude that it is possible to estimate nitrate concentrations with an uncertainty of ±1.4 µmol L −1 in the North Atlantic.
Here we present monthly, basin-wide maps of the partial pressure of carbon dioxide (pCO 2) for th... more Here we present monthly, basin-wide maps of the partial pressure of carbon dioxide (pCO 2) for the North Atlantic on a 1 • latitude by 1 • longitude grid for years 2004 through 2006 inclusive. The maps have been computed using a neural network technique which reconstructs the non-linear relationships between three biogeochemical parameters and marine pCO 2. A self organizing map (SOM) neural network has been trained using 389 000 triplets of the SeaWiFS-MODIS chlorophyll-a concentration, the NCEP/NCAR reanalysis sea surface temperature, and the FOAM mixed layer depth. The trained SOM was labelled with 137 000 underway pCO 2 measurements collected in situ during 2004, 2005 and 2006 in the North Atlantic, spanning the range of 208 to 437 µatm. The root mean square error (RMSE) of the neural network fit to the data is 11.6 µatm, which equals to just above 3 per cent of an average pCO 2 value in the in situ dataset. The seasonal pCO 2 cycle as well as estimates of the interannual variability in the major biogeochemical provinces are presented and discussed. High resolution combined with basin-wide coverage makes the maps a useful tool
The Benguela Upwelling System (BUS) is the most productive of all eastern boundary upwelling ecos... more The Benguela Upwelling System (BUS) is the most productive of all eastern boundary upwelling ecosystems and it hosts a well-developed oxygen minimum zone. As such, the BUS is a potential hotspot for production of N 2 O, a potent greenhouse gas derived from microbially driven decay of sinking organic matter. Yet, the extent at which near-surface waters emit N 2 O to the atmosphere in the BUS is highly uncertain. Here we present the first high-resolution surface measurements of N 2 O across the northern part of the BUS (nBUS). We found strong gradients with a threefold increase in N 2 O concentrations near the coast as compared with open ocean waters. Our observations show enhanced sea-to-air fluxes of N 2 O (up to 1.67 nmol m −2 s −1) in association with local upwelling cells. Based on our data we suggest that the nBUS can account for 13% of the total coastal upwelling source of N 2 O to the atmosphere. Plain Language Summary Nitrous oxide (N 2 O), commonly known as "laughing gas," is a potent greenhouse gas that contributes both to Earth's warming and to the depletion of ozone in the stratosphere. Typically, N 2 O is produced in the water column as a result of microbial decay of organic matter (under low oxygen conditions) and then it is transferred to the atmosphere at the air-sea interface. Hence, high productive regions associated with low oxygen waters could create "hotspots" for N 2 O production. Yet, emission estimates might have underestimated the potential of coastal regions due to data sparcity. We focus on the northern Benguela region, which is the most productive of four major coastal upwelling ecosystems. Here we aim to answer: what is the large-scale distribution and variability of air-sea fluxes of N 2 O? What is the impact of small-scale oceanographic features in N 2 O variability? and Do regional emissions of N 2 O need to be revisited? Based on the analysis of continuous highly resolved measurements, we suggest that the share of this region to the total N 2 O emitted by the global ocean is higher than previously thought. Considering that this region represents only 0.06% of the ocean surface, we argue that the marine budget of this gas might need revision. Eastern Boundary Upwelling Systems (EBUS) include some of the most productive regions of the ocean, accounting for about 11% of the global new production (Chavez & Toggweiler, 1995). The high productivity RESEARCH LETTER
Direct dimethyl sulfide (DMS) flux measurements using eddy covariance have shown a suppression of... more Direct dimethyl sulfide (DMS) flux measurements using eddy covariance have shown a suppression of gas transfer at medium to high wind speed. However, not all eddy covariance measurements show evidence of this suppression. Processes, such as wave-wind interaction and surfactants, have been postulated to cause this suppression. We measured DMS and carbon dioxide eddy covariance fluxes during the Asian summer monsoon in the western tropical Indian Ocean (July and August 2014). Both fluxes and their respective gas transfer velocities show signs of a gas transfer suppression above 10 m/s. Using a wind-wave interaction, we describe a flow separation process that could be responsible for a suppression of gas transfer. As a result we provide a Reynolds number-based parameterization, which states the likelihood of a gas transfer suppression for this cruise and previously published gas transfer data. Additionally, we compute the difference in the gas transfer velocities of DMS and CO 2 to estimate the bubble-mediated gas transfer using a hybrid model with three whitecap parameterizations.
The tropical Atlantic exerts a major influence in climate variability through strong air-sea inte... more The tropical Atlantic exerts a major influence in climate variability through strong air-sea interactions. Within this region, the eastern side of the equatorial band is characterized by strong seasonality, whereby the most prominent feature is the annual development of the Atlantic cold tongue (ACT). This band of low sea surface temperatures (22-238C) is typically associated with upwelling-driven enhancement of surface nutrient concentrations and primary production. Based on a detailed investigation of the distribution and sea-to-air fluxes of N 2 O in the eastern equatorial Atlantic (EEA), we show that the onset and seasonal development of the ACT can be clearly observed in surface N 2 O concentrations, which increase progressively as the cooling in the equatorial region proceeds during spring-summer. We observed a strong influence of the surface currents of the EEA on the N 2 O distribution, which allowed identifying ''high'' and ''low'' concentration regimes that were, in turn, spatially delimited by the extent of the warm eastwardflowing North Equatorial Countercurrent and the cold westward-flowing South Equatorial Current. Estimated sea-to-air fluxes of N 2 O from the ACT (mean 5.18 6 2.59 lmol m 22 d 21) suggest that in May-July 2011 this cold-water band doubled the N 2 O efflux to the atmosphere with respect to the adjacent regions, highlighting its relevance for marine tropical emissions of N 2 O.
Oceans are a net source of molecular hydrogen (H<sub>2</sub>) to the atmosphere. The ... more Oceans are a net source of molecular hydrogen (H<sub>2</sub>) to the atmosphere. The production of marine H<sub>2</sub> is assumed to be mainly biological by N<sub>2</sub> fixation, but photochemical pathways are also discussed. We present measurements of mole fraction and isotopic composition of dissolved and atmospheric H<sub>2</sub> from the southern and northern Atlantic between 2008 and 2010. In total almost 400 samples were taken during five cruises along a transect between Punta Arenas (Chile) and Bremerhaven (Germany), as well as at the coast of Mauretania. <br><br> The isotopic source signatures of dissolved H<sub>2</sub> extracted from surface water are highly deuterium-depleted and correlate negatively with temperature, showing δD values of (−629 ± 54) ‰ for water temperatures at (27 ± 3) °C and (−249 ± 88) ‰ below (19 ± 1) °C. The results for warmer water masses are consiste...
Accurate assessment of anthropogenic carbon dioxide (CO<sub>2</sub>) emissions and th... more Accurate assessment of anthropogenic carbon dioxide (CO<sub>2</sub>) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates as well as consistency within and among components, alongside methodology and data limitations. CO<sub>2</sub> emissions from fossil fuels and industry (<i>E</i><sub>FF</sub>) are based on energy statistics and cement production data, while emissions from land-use change…
Due to their high biological productivity coastal upwelling regions are important for biogeochemi... more Due to their high biological productivity coastal upwelling regions are important for biogeochemical cycles in the ocean and for fisheries. Upwelled water is not only enriched in nutrients but also supersaturated with respect to atmospheric CO 2 and N 2 O and undersaturated for O 2. We present a novel approach to estimate carbon based net community production (NCP) using surface ocean data for CO 2 , O 2 and N 2 O from three cruises to the Mauritanian upwelling region (Northwest Africa) that were conducted in different seasons. Through combination of the saturation patterns of CO 2 , O 2 and N 2 O effects of air-sea gas exchange and NCP could be separated. NCP values ranges from 0.6 ± 0.1 g C m −2 d −1 during times of weak upwelling to 1.6 ± 0.4 g C m −2 d −1 during strong upwelling. The estimated NCP values show a strong relationship with a wind derived upwelling index, which was used to estimate annual NCP.
Although hydrogen (H2) is considered as one of the most important future energy carriers, little ... more Although hydrogen (H2) is considered as one of the most important future energy carriers, little is known about the global biogeochemical cycle of this trace gas (Rhee et al. 2006). In order to assess the potential impact of expected increasing H2 concentrations to the atmosphere a fundamental understanding of the global H2 cycle is indispensable (Tromp et al. 2003, Warwick et al. 2004). Oceans are one source of atmospheric H2, produced by biological processes such as fermentation and N2-fixation and abiotic photochemical processes (Punshon and Moore 2008 and references herein). Further information can be obtained by studying the isotope composition of H2. However, the isotopic ratio of oceanic released H2 is unknown and has so far only been estimated from thermodynamic equilibrium. We investigated the atmospheric D/H isotopic ratio of H2 in the Atlantic Ocean. First results of atmospheric H2 isotope ratios from the West African coast of Mauritania and from a meridional transect over the Atlantic Ocean will be presented. Samples were taken onboard the German research vessel "Poseidon" in February 2007 associated to SOPRAN and during the cruise Ant XXIV-4 with the German research vessel "Polarstern" in April 2008 between Punta Arenas (Chile) and Bremerhaven (Germany).
Accurate assessment of anthropogenic carbon dioxide (CO 2) emissions and their redistribution amo... more Accurate assessment of anthropogenic carbon dioxide (CO 2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere-the "global carbon budget"-is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. CO 2 emissions from fossil fuels and industry (E FF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (E LUC), mainly deforestation, are based on land-cover change data and bookkeeping models. The global atmospheric CO 2 concentration is measured directly and its rate of growth (G ATM) is computed from the annual changes in concentration. The ocean CO 2 sink (S OCEAN) and terrestrial CO 2 sink (S LAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (B IM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2007-2016), E FF was 9.4 ± 0.
As a response to public demand for a welldocumented, quality controlled, publically available, gl... more As a response to public demand for a welldocumented, quality controlled, publically available, global surface ocean carbon dioxide (CO 2) data set, the international marine carbon science community developed the Surface Ocean CO 2 Atlas (SOCAT). The first SOCAT product is a collection of 6.3 million quality controlled surface CO 2 data from the global oceans and coastal seas, spanning four decades (1968-2007). The SOCAT gridded data presented here is the second data product to come from the SOCAT project. Recognizing that some groups may have trouble working with millions of measurements, the SOCAT gridded product was generated to provide a robust, regularly spaced CO 2 fugacity (f CO 2) product with minimal spatial and temporal interpolation, which should be easier to work with for many applications. Gridded SOCAT is rich with information that has not been fully explored yet (e.g., regional differences in the seasonal cycles), but also contains biases and limitations that the user needs to recognize and address (e.g., local influences on values in some coastal regions).
The oceans are a major sink for atmospheric carbon dioxide (CO 2). Historically, observations hav... more The oceans are a major sink for atmospheric carbon dioxide (CO 2). Historically, observations have been too sparse to allow accurate tracking of changes in rates of CO 2 uptake over ocean basins, so little is known about how these vary. Here, we show observations indicating substantial variability in the CO 2 uptake by the North Atlantic on time scales of a few years. Further, we use measurements from a coordinated network of instrumented commercial ships to define the annual flux into the North Atlantic, for the year 2005, to a precision of about 10%. This approach offers the prospect of accurately monitoring the changing ocean CO 2 sink for those ocean basins that are well covered by shipping routes.
A new system for continuous, highly-resolved oceanic and atmospheric measurements of N 2 O, CO an... more A new system for continuous, highly-resolved oceanic and atmospheric measurements of N 2 O, CO and CO 2 is described. The system is based upon off-axis integrated cavity output spectroscopy (OA-ICOS) and a non-dispersive infrared analyzer (NDIR) both coupled to a Weiss-type equilibrator. Performance of the combined setup was evaluated by testing its precision, accuracy, long-term stability, linearity and response time. Furthermore, the setup was tested during two oceanographic campaigns in the equatorial Atlantic Ocean in order to explore its potential for autonomous deployment onboard voluntary observing ships (VOS). Improved equilibrator response times for N 2 O (2.5 min) and CO (45 min) were achieved in comparison to response times from similar
The role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the ... more The role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the flux strengths between the ocean and the atmosphere can be quantified by measuring the fugacity of CO 2 (ƒCO 2) as well as the dissolved inorganic carbon (DIC) concentration and its isotopic composition in surface seawater. In this work, the potential of continuous wave cavity ringdown spectroscopy (cw-CRDS) for autonomous underway measurements of ƒCO 2 and the stable carbon isotope ratio of DIC [δ 13 C(DIC)] is explored. For the first time, by using a conventional air-sea equilibrator setup, both quantities were continuously and simultaneously recorded during a field deployment on two research cruises following meridional transects across the Atlantic Ocean (Bremerhaven, Germany-Punta Arenas, Chile). Data are compared against reference measurements by an established underway CO 2 monitoring system and isotope ratio mass spectrometric analysis of individual water samples. Agreement within ΔƒCO 2 = 0.35 μatm for atmospheric and ΔƒCO 2 = 2.5 μatm and Δδ 13 C(DIC) = 0.33‰ for seawater measurements have been achieved. Whereas "calibration-free" ƒCO 2 monitoring is feasible, the measurement of accurate isotope ratios relies on running reference standards on a daily basis. Overall, the installed CRDS/equilibrator system was shown to be capable of reliable online monitoring of ƒCO 2 , equilibrium δ 13 C(CO 2), δ 13 C(DIC), and pO 2 aboard moving research vessels, thus making possible corresponding measurements with high spatial and temporal resolution.
Gross photosynthetic O 2 production (GOP) rates in the subpolar North Atlantic Ocean were estimat... more Gross photosynthetic O 2 production (GOP) rates in the subpolar North Atlantic Ocean were estimated using the measured isotopic composition of dissolved oxygen in the surface layer on samples collected on nine transits of a container ship between Great Britain and Canada during March 2007 to June 2008. The mean basin-wide GOP rate of 226 AE 48 mmol O 2 m À2 d À1 during summer was double the winter rate of 107 AE 41 mmol O 2 m À2 d À1. Converting these GOP rates to equivalent 14 C-based PP (14 C-PP eqv) yielded rates of 1005 AE 216 and 476 AE 183 mg C m À2 d À1 in summer and winter, respectively, that generally agreed well with previous 14 C-based PP estimates in the region. The 14 C-PP eqv estimates were 1-1.6Â concurrent satellite-based PP estimates along the cruise track. A net community production rate (NCP) of 87 AE 12 mmol O 2 m À2 d À1 (62 AE 9 mmol C m À2 d À1) and NCP/GOP of 0.35 AE 0.06 in the mixed layer was estimated from O 2 /Ar and 17 D measurements (61 N 26 W) during spring bloom conditions in May 2008. Contrastingly, a much lower long-term annual mean NCP or organic carbon export rate of 2.8 AE 2.7 mol C m À2 yr À1 (8 AE 7 mmol C m À2 d À1) and NCP/GOP of 0.07 AE 0.06 at the winter mixed layer depth was estimated from 15 years of surface O 2 data in the subpolar N. Atlantic collected during the CARINA program.
Deep Sea Research Part II: Topical Studies in Oceanography, 2009
Corrigendum to Climatological mean and decadal change in surface ocean pCO 2 , and net seaair C... more Corrigendum to Climatological mean and decadal change in surface ocean pCO 2 , and net seaair CO 2 flux over the global oceans [Deep Sea Res. II 56 (2009) 554577] Deep Sea Research Part I: Oceanographic Research Papers, Volume 56, Issue 11, November 2009, Pages ...
Deep Sea Research Part I: Oceanographic Research Papers, 2009
Corrigendum to ''Climatological mean and decadal change in surface ocean pCO 2 , and net sea-air ... more Corrigendum to ''Climatological mean and decadal change in surface ocean pCO 2 , and net sea-air CO 2 flux over the global oceans'' [Deep Sea Res. II 56 (2009) 554-577]
Here we present an equation for the estimation of nitrate in surface waters of the North Atlantic... more Here we present an equation for the estimation of nitrate in surface waters of the North Atlantic Ocean (40 • N to 52 • N, 10 • W to 60 • W). The equation was derived by multiple linear regression (MLR) from nitrate, sea surface temperature (SST) observational data and model mixed layer depth (MLD) data. The observational data were taken from merchant vessels that have crossed the North Atlantic on a regular basis in 2002/2003 and from 2005 to the present. It is important to find a robust and realistic estimate of MLD because the deepening of the mixed layer is crucial for nitrate supply to the surface. We compared model data from two models (FOAM and Mercator) with MLD derived from float data (using various criteria). The Mercator model gives a MLD estimate that is close to the MLD derived from floats. MLR was established using SST, MLD from Mercator, time and latitude as predictors. Additionally a neural network was trained with the same dataset and the results were validated against both model data as a "ground truth" and an independent observational dataset. This validation produced RMS errors of the same order for MLR and the neural network approach. We conclude that it is possible to estimate nitrate concentrations with an uncertainty of ±1.4 µmol L −1 in the North Atlantic.
Here we present monthly, basin-wide maps of the partial pressure of carbon dioxide (pCO 2) for th... more Here we present monthly, basin-wide maps of the partial pressure of carbon dioxide (pCO 2) for the North Atlantic on a 1 • latitude by 1 • longitude grid for years 2004 through 2006 inclusive. The maps have been computed using a neural network technique which reconstructs the non-linear relationships between three biogeochemical parameters and marine pCO 2. A self organizing map (SOM) neural network has been trained using 389 000 triplets of the SeaWiFS-MODIS chlorophyll-a concentration, the NCEP/NCAR reanalysis sea surface temperature, and the FOAM mixed layer depth. The trained SOM was labelled with 137 000 underway pCO 2 measurements collected in situ during 2004, 2005 and 2006 in the North Atlantic, spanning the range of 208 to 437 µatm. The root mean square error (RMSE) of the neural network fit to the data is 11.6 µatm, which equals to just above 3 per cent of an average pCO 2 value in the in situ dataset. The seasonal pCO 2 cycle as well as estimates of the interannual variability in the major biogeochemical provinces are presented and discussed. High resolution combined with basin-wide coverage makes the maps a useful tool
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Papers by T. Steinhoff