| 1. |
- Olsen, Are, 1972, et al.
(author)
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Nordic seas transit time distributions and anthropogenic CO2
- 2010
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In: Journal of Geophysical Research Oceans. - 0148-0227. ; 115
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Journal article (peer-reviewed)abstract
- The distribution and inventory of anthropogenic carbon (DICant) in the Nordic seas are determined using the transit time distribution (TTD) approach. To constrain the shape of the TTDs in the Nordic seas, CO2 is introduced as an age tracer and used in combination with water age estimates determined from CFC-12 data. CO2 and CFC-12 tracer ages constitute a very powerful pair for constraining the shape of TTDs. The highest concentrations of DICant appear in the warm and well-ventilated Atlantic water that flows into the region from the south, and concentrations are typically lower moving west into the colder Arctic surface waters. The depth distribution of DICant reflects the extent of ventilation in the different areas. The Nordic seas DICant inventory for 2002 was constrained to between 0.9 and 1.4 Gt DICant, corresponding to ∼1% of the global ocean DICant inventory. The TTD-derived DICant estimates were compared with estimates derived using four other approaches, revealing significant differences with respect to the TTD-derived estimates, which can be related to issues with some of the underlying assumptions of these other approaches. Specifically, the Tracer combining Oxygen, inorganic Carbon and total Alkalinity (TrOCA) method appears to underestimate DICant in the Nordic seas, the ΔC* shortcut and the approach of Jutterström et al. (2008) appear to overestimate DICant at most depths in this area, and finally the approach of Tanhua et al. (2007) appears to underestimate Nordic seas DICant below 3000 m and overestimate it above 1000 m.
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| 2. |
- Olsen, Are, 1972, et al.
(author)
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Overview of the Nordic Seas CARINA data and salinity measurements
- 2009
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In: Earth System Science Data Discussions. - 1866-3591. ; 2, s. 1-25
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Journal article (peer-reviewed)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.
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| 3. |
- Chierici, Melissa, 1968, et al.
(author)
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Algorithms to estimate carbon dioxide in the upper subarctic North Atlantic using observations, satellite and ocean analysis data
- 2009
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In: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645. ; 56, s. 630-639
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Journal article (peer-reviewed)abstract
- Observations of the surface-water fugacity of carbon dioxide (fCO2sw) measured during 2005 in the subpolar North Atlantic Ocean (58–62°N, 10–40°W) were used together with in situ ocean data and remotely sensed data to develop algorithms to estimate fCO2sw. Based on multiple regression we found that sea-surface temperature (SST), mixed-layer depth (MLD), and chlorophyll a (chl a) contributed significantly to the fit. Two algorithms were developed for periods depending on the presence of chl a data. The correlation coefficient (r2) and the root-mean-square deviation (rms) for the best fit in the period when chl a was observed (20 March–15 October) were 0.720 and ±10.8 μatm, respectively. The best fit for the algorithm for the period when no chl a was present (16 October–19 March) resulted in a r2 of 0.774 and a rms of ±5.6 μatm. Based on these algorithms we estimated seasonal fields of fCO2sw and the air–sea CO2 flux. The estimated net annual CO2 sink was 0.0058 Gt C yr−1 or 0.6 mol C m−2 yr−1.
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| 4. |
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| 5. |
- Chierici, Melissa, 1968, et al.
(author)
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Surface water fCO2 algorithms for the high-latitude Pacific sector of the Southern Ocean
- 2012
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In: Remote Sensing of Environment. - : Elsevier BV. - 0034-4257. ; 119, s. 184-196
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Journal article (peer-reviewed)abstract
- The feasibility of using remotely sensed data jointly with shipboard measurements to estimate the carbon dioxide fugacity in the surface water (fCO2sw) of the Pacific sector of the Southern Polar Ocean (S > 60°S) is evaluated using a data set obtained during austral summer 2006. A comparison between remotely sensed chlorophyll a (chl a) and sea-surface temperature (SST) with in-situ measurements, reveals the largest bias in areas with rapid and large concentration changes such as at the ice edge, the polar front and in the Ross Sea Polynya. The correlation between fCO2sw and SST, chl a, biological productivity estimates and mixed layer depth (MLD) are evaluated, and single and multiple regression methods are used to develop fCO2sw algorithms. Single regressions between the study parameters and fCO2sw show that most of the fCO2sw variability is explained by chl a. The Multi-Parameter Linear regressions were used to create fCO2sw algorithms derived from field measurements, and using solely remote-sensing products. Based on the best fits from the two data sets fCO2sw estimates have a root means square deviation of ± 14 μatm and coefficient of determination of 0.82. The addition of satellite derived estimates of biological productivity in the algorithm does not significantly improve the fit. We use the algorithm with remotely sensed chl a and SST data to produce an fCO2sw map for the entire high-latitude Southern Ocean south of 55°S. We analyze and discuss the seasonal and spatial robustness of the algorithm based on the remotely sensed data and compare with climatologic fCO2sw data.
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| 6. |
- Jutterström, Sara, 1975, et al.
(author)
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Arctic Ocean data in CARINA
- 2009
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In: Earth Syst. Sci. Data Discuss.. - : Copernicus GmbH. ; 2, s. 281-308
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Journal article (peer-reviewed)abstract
- The paper describes the steps taken for quality controlling chosen parameters within the Arctic Ocean data included in the CARINA data set and checking for offsets between the individual cruises. The evaluated parameters are the inorganic carbon parameters (total dissolved inorganic carbon, total alkalinity and pH), oxygen and nutrients: nitrate, phosphate and silicate. More parameters can be found in the CARINA data product, but were not subject to a secondary quality control. The main method in determining offsets between cruises was regional multi-linear regression, after a first rough basin-wide deep-water estimate of each parameter. Lastly, the results of the secondary quality control are discussed as well as suggested adjustments.
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| 7. |
- Metzl, Nicolas, et al.
(author)
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Recent acceleration of the sea surface fCO2 growth rate in the North Atlantic subpolar gyre (1993–2008) revealed by winter observations
- 2010
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In: GLOBAL BIOGEOCHEMICAL CYCLES. - 0886-6236. ; 24
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Journal article (peer-reviewed)abstract
- Recent studies based on ocean and atmospheric carbon dioxide (CO2) observations, suggesting that the ocean carbon uptake has been reduced, may help explain the increase in the fraction of anthropogenic CO2 emissions that remain in the atmosphere. Is it a response to climate change or a signal of ocean natural variability or both? Regional process analyses are needed to follow the ocean carbon uptake and to enable better attributions of the observed changes. Here, we describe the evolution of the surface ocean CO2 fugacity (fCO2 oc) over the period 1993–2008 in the North Atlantic subpolar gyre (NASPG). This analysis is based primarily on observations of dissolved inorganic carbon (DIC) and total alkalinity (TA) conducted at different seasons in the NASPG between Iceland and Canada. The fCO2 oc trends based on DIC and TA data are also compared with direct fCO2 measurements obtained between 2003 and 2007 in the same region. During winters 1993–2003, the fCO2 oc growth rate was 3.7 (±0.6) matm yr−1, higher than in the atmosphere, 1.8 (±0.1) matm yr−1. This translates to a reduction of the ocean carbon uptake primarily explained by sea surface warming, up to 0.24 (±0.04) °C yr−1. This warming is a consequence of advection of warm water northward from the North Atlantic into the Irminger basin, which occurred as the North Atlantic Oscillation (NAO) index moved into a negative phase in winter 1995/1996. In winter 2001–2008, the fCO2 oc rise was particularly fast, between 5.8 (±1.1) and 7.2 (±1.3) matm yr−1 depending on the region, more than twice the atmospheric growth rate of 2.1 (±0.2) matm yr−1, and in the winter of 2007–2008 the area was supersaturated with CO2. As opposed to the 1990s, this appears to be almost entirely due to changes in seawater carbonate chemistry, the combination of increasing DIC and decreasing of TA. The rapid fCO2 oc increase was not only driven by regional uptake of anthropogenic CO2 but was also likely controlled by a recent increase in convective processes‐vertical mixing in the NASPG and cannot be directly associated with NAO variability. The fCO2 oc increase observed in 2001–2008 leads to a significant drop in pH of −0.069 (±0.007) decade−1.
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| 8. |
- Nondal, Gisle, et al.
(author)
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Optimal evaluation of the surface ocean CO2 system in the northern North Atlantic using data from voluntary observing ships
- 2009
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In: Limnology and Oceanography : Methods. - 1541-5856. ; 7, s. 109-118
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Journal article (peer-reviewed)abstract
- This work evaluates whether an accurate calculation of the entire CO2 system in the northern North Atlantic can be carried out using a combination of in situ fugacity of CO2 (fCO2) and ancillary data often measured on Voluntary Observing Ships (VOS), i.e., sea surface temperature (SST) and sea surface salinity (SSS), as well as nitrate (NO3 –). Two approaches are tested: (I) determination of At from SSS and then calculating Ct from measured fCO2 and estimated At; and (II) determination of Ct from SSS, SST, and NO3 – and then calculating At from measured fCO2 and estimated Ct. The optimal approach was found to be determination of At from SSS and then calculating Ct from measured fCO2 and estimated At. This allowed At to be determined with a mean bias of –1.8 μmol kg–1 and root mean square (rms) deviation 6.2 μmol kg–1 and then Ct to be calculated with a mean bias of –1.0 μmol kg–1 and standard error of calculation of 7.4 μmol kg–1, as validated using independent data sets.
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| 9. |
- Olsen, Are, 1972
(author)
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Nordic Seas total dissolved inorganic carbon data in CARINA
- 2009
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In: Earth System Science Data. - 1866-3508 .- 1866-3516. ; 1, s. 35-43
-
Journal article (peer-reviewed)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 presents an account of the quality control of the total dissolved inorganic carbon (TCO2) data from the Nordic Seas in CARINA. Out of the 35 cruises from the Nordic Seas included in CARINA, 25 had TCO2 data. The data from 7 of these were found to be of low quality and should not be used, thus the final CARINA data product contains TCO2 data from 18 cruises from the Nordic Seas. These data appear consistent to at least 4 μmol kg−1.
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| 10. |
- Olsen, Are, 1972, et al.
(author)
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Sea-surface CO2 partial pressure in the subpolar North Atlantic
- 2008
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In: Biogeosciences. ; 5, s. 535-547
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Journal article (peer-reviewed)abstract
- We present the first year-long subpolar trans-Atlantic set of surface seawater CO2 fugacity (fCO2sw) data. The data were obtained aboard the MV Nuka Arctica in 2005 and provide a quasi-continuous picture of the fCO2sw variability between Denmark and Greenland. Complementary real-time high-resolution data of surface chlorophyll-a (chl-a) concentrations and mixed layer depth (MLD) estimates have been collocated with the fCO2sw data. Off-shelf fCO2sw data exhibit a pronounced seasonal cycle. In winter, surface waters are saturated to slightly supersaturated over a wide range of temperatures. Through spring and summer, fCO2sw decreases by approximately 60 μatm, due to biological carbon consumption, which is not fully counteracted by the fCO2sw increase due to summer warming. The changes are synchronous with changes in chl-a concentrations and MLD, both of which are exponentially correlated with fCO2sw in off-shelf regions.
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