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3. Quantitative Assessment of Factors Contributing to Variations in Sea Surface pCO2 in the Pacific Sector of the Arctic Ocean.

Author

Tozawa, Manami, Nomura, Daiki, Matsuura, Mirai, Hatta, Mariko, Fujiwara, Amane, Yasunaka, Sayaka, and Murata, Akihiko

Subjects
ATMOSPHERIC carbon dioxide, OCEAN, PARTIAL pressure, LANGUAGE ability testing, WATER chemistry, SEA ice, CARBON dioxide
Abstract

To quantitatively assess seasonal variations in the partial pressure of carbon dioxide (pCO2) in the Pacific sector of the Arctic Ocean (Canada Basin and Chukchi Sea) in 2021, water temperature, salinity, chlorophyll‐a, pCO2, dissolved inorganic carbon (DIC), total alkalinity (TA), and nutrients were measured. During summer 2021, surface water pCO2 in our study area (315 ± 41 μatm) was undersaturated with respect to the atmosphere (404 ± 4 μatm), and the ocean was a sink for atmospheric CO2 (−10.5 ± 11.0 mmol C m−2 day−1). Using DIC, TA, and nutrients in the temperature minimum layer, we estimated the under‐ice pCO2 in the water during the previous winter and calculated changes in pCO2 (δpCO2) due to temperature changes, freshwater inflow, biological activity, and other factors (gas exchange and advection) from winter to summer. In the Chukchi Sea, biological activity and temperature changes had significant impacts on pCO2, whereas in the Canada Basin, the influx of freshwater caused a significant decrease in pCO2. Our results suggested that different types of freshwaters had different effects on pCO2, with sea ice meltwater having a greater effect on reducing pCO2 than river water or snowmelt water. We therefore emphasize the importance of freshwater type and proportion, as well as freshwater supply, for prediction of future pCO2 changes. Plain Language Summary: Assessment of the factors that cause ocean CO2 to vary is important in the Arctic Ocean, which acts as an atmospheric CO2 sink that will change significantly because of global warming. Seawater and sea ice samples were collected in the Pacific sector of the Arctic Ocean to investigate the carbonate chemistry. The partial pressure of carbon dioxide (pCO2) was lower on the sea surface than in the atmosphere during summer, and the ocean absorbed atmospheric CO2. The decreases of pCO2 from winter to summer were driven primarily by biological activity in the Chukchi Sea (partially offset by temperature increases) and by freshwater additions in the Canada Basin. Sea ice meltwater, snow meltwater, and river water had different effects on pCO2, even though all of them diluted the carbonate concentrations of surface water, because of differences in the alkalinity and carbonate chemistry among these freshwater sources. Key Points: The Pacific sector of the Arctic Ocean absorbed atmospheric CO2 in summerIn the Chukchi Sea, biological activity and temperature changed pCO2, while in the Canada Basin, the freshwater caused a decrease in pCO2Sea ice meltwater had a greater effect on reducing pCO2 than river water or snow meltwater [ABSTRACT FROM AUTHOR]

Published
2024
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5. An Assessment of CO2 Uptake in the Arctic Ocean From 1985 to 2018

Author

Yasunaka, Sayaka, primary, Manizza, Manfredi, additional, Terhaar, Jens, additional, Olsen, Are, additional, Yamaguchi, Ryohei, additional, Landschützer, Peter, additional, Watanabe, Eiji, additional, Carroll, Dustin, additional, Adiwira, Hanani, additional, Müller, Jens Daniel, additional, and Hauck, Judith, additional

Published
2023
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6. Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

Author

DeVries, Tim, primary, Yamamoto, Kana, additional, Wanninkhof, Rik, additional, Gruber, Nicolas, additional, Hauck, Judith, additional, Müller, Jens Daniel, additional, Bopp, Laurent, additional, Carroll, Dustin, additional, Carter, Brendan, additional, Chau, Thi‐Tuyet‐Trang, additional, Doney, Scott C., additional, Gehlen, Marion, additional, Gloege, Lucas, additional, Gregor, Luke, additional, Henson, Stephanie, additional, Kim, Ji Hyun, additional, Iida, Yosuke, additional, Ilyina, Tatiana, additional, Landschützer, Peter, additional, Le Quéré, Corinne, additional, Munro, David, additional, Nissen, Cara, additional, Patara, Lavinia, additional, Pérez, Fiz F., additional, Resplandy, Laure, additional, Rodgers, Keith B., additional, Schwinger, Jörg, additional, Séférian, Roland, additional, Sicardi, Valentina, additional, Terhaar, Jens, additional, Triñanes, Joaquin, additional, Tsujino, Hiroyuki, additional, Watson, Andrew, additional, Yasunaka, Sayaka, additional, and Zeng, Jiye, additional

Published
2023
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8. An assessment of sea-air CO2 flux in the Arctic Ocean from 1985 to 2018

Author

Yasunaka, Sayaka, primary, Manizza, Manfredi, additional, Terhaar, Jens, additional, Olsen, Are, additional, Yamaguchi, Ryohei, additional, Landschützer, Peter, additional, Watanabe, Eiji, additional, Carroll, Dustin, additional, Adiwira, Hanani, additional, Müller, Jens, additional, and Hauck, Judith, additional

Published
2023
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9. An Assessment of CO2 Uptake in the Arctic Ocean From 1985 to 2018

Author

Yasunaka, Sayaka, Manizza, Manfredi, Terhaar, Jens, Olsen, Are, Yamaguchi, Ryohei, Landschützer, Peter, Watanabe, Eiji, Carroll, Dustin, Adiwira, Hanani, Müller, Jens Daniel, Hauck, Judith, Yasunaka, Sayaka, Manizza, Manfredi, Terhaar, Jens, Olsen, Are, Yamaguchi, Ryohei, Landschützer, Peter, Watanabe, Eiji, Carroll, Dustin, Adiwira, Hanani, Müller, Jens Daniel, and Hauck, Judith

Abstract

As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of Arctic Ocean sea-air CO2 fluxes and their uncertainties from surface ocean pCO2-observation products, ocean biogeochemical hindcast and data assimilation models, and atmospheric inversions. For the period of 1985–2018, the Arctic Ocean was a net sink of CO2 of 116 ± 4 TgC yr−1 in the pCO2 products, 92 ± 30 TgC yr−1 in the models, and 91 ± 21 TgC yr−1 in the atmospheric inversions. The CO2 uptake peaks in late summer and early autumn, and is low in winter when sea ice inhibits sea-air fluxes. The long-term mean CO2 uptake in the Arctic Ocean is primarily caused by steady-state fluxes of natural carbon (70% ± 15%), and enhanced by the atmospheric CO2 increase (19% ± 5%) and climate change (11% ± 18%). The annual mean CO2 uptake increased from 1985 to 2018 at a rate of 31 ± 13 TgC yr−1 dec−1 in the pCO2 products, 10 ± 4 TgC yr−1 dec−1 in the models, and 32 ± 16 TgC yr−1 dec−1 in the atmospheric inversions. Moreover, 77% ± 38% of the trend in the net CO2 uptake over time is caused by climate change, primarily due to rapid sea ice loss in recent years. Furthermore, true uncertainties may be larger than the given ensemble standard deviations due to common structural biases across all individual estimates.

Published
2023

10. Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

Author

DeVries, Tim, Yamamoto, Kana, Wanninkhof, Rik, Gruber, Nicolas, Hauck, Judith, Müller, Jens Daniel, Bopp, Laurent, Carroll, Dustin, Carter, Brendan, Chau, Thi‐Tuyet‐Trang, Doney, Scott C, Gehlen, Marion, Gloege, Lucas, Gregor, Luke, Henson, Stephanie, Kim, Ji Hyun, Iida, Yosuke, Ilyina, Tatiana, Landschützer, Peter, Le Quéré, Corinne, Munro, David, Nissen, Cara, Patara, Lavinia, Pérez, Fiz F, Resplandy, Laure, Rodgers, Keith B, Schwinger, Jörg, Séférian, Roland, Sicardi, Valentina, Terhaar, Jens, Triñanes, Joaquin, Tsujino, Hiroyuki, Watson, Andrew, Yasunaka, Sayaka, Zeng, Jiye, DeVries, Tim, Yamamoto, Kana, Wanninkhof, Rik, Gruber, Nicolas, Hauck, Judith, Müller, Jens Daniel, Bopp, Laurent, Carroll, Dustin, Carter, Brendan, Chau, Thi‐Tuyet‐Trang, Doney, Scott C, Gehlen, Marion, Gloege, Lucas, Gregor, Luke, Henson, Stephanie, Kim, Ji Hyun, Iida, Yosuke, Ilyina, Tatiana, Landschützer, Peter, Le Quéré, Corinne, Munro, David, Nissen, Cara, Patara, Lavinia, Pérez, Fiz F, Resplandy, Laure, Rodgers, Keith B, Schwinger, Jörg, Séférian, Roland, Sicardi, Valentina, Terhaar, Jens, Triñanes, Joaquin, Tsujino, Hiroyuki, Watson, Andrew, Yasunaka, Sayaka, and Zeng, Jiye

Abstract

This contribution to the RECCAP2 (REgional Carbon Cycle Assessment and Processes) assessment analyzes the processes that determine the global ocean carbon sink, and its trends and variability over the period 1985–2018, using a combination of models and observation-based products. The mean sea-air CO2 flux from 1985 to 2018 is −1.6 ± 0.2 PgC yr−1 based on an ensemble of reconstructions of the history of sea surface pCO2 (pCO2 products). Models indicate that the dominant component of this flux is the net oceanic uptake of anthropogenic CO2, which is estimated at −2.1 ± 0.3 PgC yr−1 by an ensemble of ocean biogeochemical models, and −2.4 ± 0.1 PgC yr−1 by two ocean circulation inverse models. The ocean also degasses about 0.65 ± 0.3 PgC yr−1 of terrestrially derived CO2, but this process is not fully resolved by any of the models used here. From 2001 to 2018, the pCO2 products reconstruct a trend in the ocean carbon sink of −0.61 ± 0.12 PgC yr−1 decade−1, while biogeochemical models and inverse models diagnose an anthropogenic CO2-driven trend of −0.34 ± 0.06 and −0.41 ± 0.03 PgC yr−1 decade−1, respectively. This implies a climate-forced acceleration of the ocean carbon sink in recent decades, but there are still large uncertainties on the magnitude and cause of this trend. The interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate-driven variability exceeding the CO2-forced variability by 2–3 times. These results suggest that anthropogenic CO2 dominates the ocean CO2 sink, while climate-driven variability is potentially large but highly uncertain and not consistently captured across different methods.

Published
2023

11. Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

Author

National Science Foundation (US), National Oceanic and Atmospheric Administration (US), European Commission, Helmholtz Association, National Aeronautics and Space Administration (US), Research Foundation - Flanders, German Research Foundation, Ministerio de Ciencia e Innovación (España), Research Council of Norway, Swiss National Science Foundation, Royal Society (UK), Devries, Timothy, Yamamoto, Kama, Wanninkhof, Rik, Gruber, Nicolas, Hauck, Judith, Müller, Jens Daniel, Bopp, Laurent, Carroll, Dustin, Carter, Brendan R., Chau, Thi-Tuyet-Trang, Doney, Scott C., Gehlen, Marion, Gloege, Lucas, Gregor, Luke, Henson, Stephanie, Kim, Ji Hyun, Iida, Yosuke, Ilyina, Tatiana, Landschützer, Peter, Le Quéré, Corinne, Munro, David R., Nissen, Cara, Patara, Lavinia, Pérez, Fiz F., Resplandy, Laure, Rodgers, Keith B., Schwinger, Jörg, Séférian, Roland, Sicardi, Valentina, Terhaar, Jens, Triñanes, Joaquin, Tsujino, Hiroyuki, Watson, Andrew J., Yasunaka, Sayaka, Zeng, Jiye, National Science Foundation (US), National Oceanic and Atmospheric Administration (US), European Commission, Helmholtz Association, National Aeronautics and Space Administration (US), Research Foundation - Flanders, German Research Foundation, Ministerio de Ciencia e Innovación (España), Research Council of Norway, Swiss National Science Foundation, Royal Society (UK), Devries, Timothy, Yamamoto, Kama, Wanninkhof, Rik, Gruber, Nicolas, Hauck, Judith, Müller, Jens Daniel, Bopp, Laurent, Carroll, Dustin, Carter, Brendan R., Chau, Thi-Tuyet-Trang, Doney, Scott C., Gehlen, Marion, Gloege, Lucas, Gregor, Luke, Henson, Stephanie, Kim, Ji Hyun, Iida, Yosuke, Ilyina, Tatiana, Landschützer, Peter, Le Quéré, Corinne, Munro, David R., Nissen, Cara, Patara, Lavinia, Pérez, Fiz F., Resplandy, Laure, Rodgers, Keith B., Schwinger, Jörg, Séférian, Roland, Sicardi, Valentina, Terhaar, Jens, Triñanes, Joaquin, Tsujino, Hiroyuki, Watson, Andrew J., Yasunaka, Sayaka, and Zeng, Jiye

Abstract

This contribution to the RECCAP2 (REgional Carbon Cycle Assessment and Processes) assessment analyzes the processes that determine the global ocean carbon sink, and its trends and variability over the period 1985–2018, using a combination of models and observation-based products. The mean sea-air CO2 flux from 1985 to 2018 is −1.6 ± 0.2 PgC yr−1 based on an ensemble of reconstructions of the history of sea surface pCO2 (pCO2 products). Models indicate that the dominant component of this flux is the net oceanic uptake of anthropogenic CO2, which is estimated at −2.1 ± 0.3 PgC yr−1 by an ensemble of ocean biogeochemical models, and −2.4 ± 0.1 PgC yr−1 by two ocean circulation inverse models. The ocean also degasses about 0.65 ± 0.3 PgC yr−1 of terrestrially derived CO2, but this process is not fully resolved by any of the models used here. From 2001 to 2018, the pCO2 products reconstruct a trend in the ocean carbon sink of −0.61 ± 0.12 PgC yr−1 decade−1, while biogeochemical models and inverse models diagnose an anthropogenic CO2-driven trend of −0.34 ± 0.06 and −0.41 ± 0.03 PgC yr−1 decade−1, respectively. This implies a climate-forced acceleration of the ocean carbon sink in recent decades, but there are still large uncertainties on the magnitude and cause of this trend. The interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate-driven variability exceeding the CO2-forced variability by 2–3 times. These results suggest that anthropogenic CO2 dominates the ocean CO2 sink, while climate-driven variability is potentially large but highly uncertain and not consistently captured across different methods

Published
2023

12. Constraining regional and global ocean carbon fluxes 1985 to 2018 in RECCAP2

Author

Hauck, Judith, Gruber, Nicolas, Ishii, Masao, Müller, Jens Daniel, Carter, Brendan R., Dai, Minhan, Devries, Timothy, Doney, Scott C., Fassbender, Andrea J., Gehlen, Marion, Goris, Nadine, Gregor, Luke, Henson, Stephanie, Lachkar; Zouhair, Landschützer, Peter, Laruelle, Goulven, Manizza, Manfredi, Olsen, Are, Pérez, Fiz F., Regnier, Pierre, Resplandy, Laure, Rodgers, Keith B., Sarma, V. V. S. S., Schwinger, Jörg, Terhaar, Jens, Tjiputra, Jerry, Wanninkhof, Rik, Yasunaka, Sayaka, Canadell, Josep G., Hauck, Judith, Gruber, Nicolas, Ishii, Masao, Müller, Jens Daniel, Carter, Brendan R., Dai, Minhan, Devries, Timothy, Doney, Scott C., Fassbender, Andrea J., Gehlen, Marion, Goris, Nadine, Gregor, Luke, Henson, Stephanie, Lachkar; Zouhair, Landschützer, Peter, Laruelle, Goulven, Manizza, Manfredi, Olsen, Are, Pérez, Fiz F., Regnier, Pierre, Resplandy, Laure, Rodgers, Keith B., Sarma, V. V. S. S., Schwinger, Jörg, Terhaar, Jens, Tjiputra, Jerry, Wanninkhof, Rik, Yasunaka, Sayaka, and Canadell, Josep G.

Abstract

Keeping global warming in line with the Paris Agreement requires rapid reductions in CO2 emissions. Tracking these reductions demands a thorough bookkeeping of natural and anthropogenic carbon fluxes. The second REgional Carbon Cycle Assessment and Processes (RECCAP2) activity of the Global Carbon Project aims to accurately assess land and ocean CO2 sources and sinks through the efforts of hundreds of scientists around the globe. For the ocean component, regional budgets are developed for the global ocean and five large regions for the period 1980-2018. In addition, four ‘special focus’ themes, namely the biological carbon pump, the seasonal cycle, the coastal ocean and model evaluation are addressed. We use state-of-the-art ocean models and observation-based datasets to provide robust estimates of regional CO2 budgets and constrain their uncertainties. Here, we will provide an overview of RECCAP2 activities, and showcase key results focusing on mean ocean carbon fluxes, and their trends and variability

Published
2023

13. RECCAP2-ocean: Regional Carbon Cycle Assessment and Processes Phase 2

Author

Müller, Jens Daniel, Hauck, Judith, Gruber, Nicolas, Ishii, Masao, Carter, Brendan R., Dai, Minhan, Devries, Timothy, Doney, Scott C., Fassbender, Andrea J., Gehlen, Marion, Goris, Nadine, Gregor, Luke, Henson, Stephanie, Lachkar; Zouhair, Landschützer, Peter, Laruelle, Goulven, Manizza, Manfredi, Olsen, Are, Pérez, Fiz F., Regnier, Pierre, Resplandy, Laure, Rodgers, Keith B., Sarma, V. V. S. S., Schwinger, Jörg, Terhaar, Jens, Tjiputra, Jerry, Wanninkhof, Rik, Yasunaka, Sayaka, Bastos, Ana, Poulter, Benjamin, Canadell, Josep G., Müller, Jens Daniel, Hauck, Judith, Gruber, Nicolas, Ishii, Masao, Carter, Brendan R., Dai, Minhan, Devries, Timothy, Doney, Scott C., Fassbender, Andrea J., Gehlen, Marion, Goris, Nadine, Gregor, Luke, Henson, Stephanie, Lachkar; Zouhair, Landschützer, Peter, Laruelle, Goulven, Manizza, Manfredi, Olsen, Are, Pérez, Fiz F., Regnier, Pierre, Resplandy, Laure, Rodgers, Keith B., Sarma, V. V. S. S., Schwinger, Jörg, Terhaar, Jens, Tjiputra, Jerry, Wanninkhof, Rik, Yasunaka, Sayaka, Bastos, Ana, Poulter, Benjamin, and Canadell, Josep G.

Published
2023

14. An Assessment of CO2 Uptake in the Arctic Ocean From 1985 to 2018.

Author

Yasunaka, Sayaka, Manizza, Manfredi, Terhaar, Jens, Olsen, Are, Yamaguchi, Ryohei, Landschützer, Peter, Watanabe, Eiji, Carroll, Dustin, Adiwira, Hanani, Müller, Jens Daniel, and Hauck, Judith

Subjects
CARBON cycle, ATMOSPHERIC carbon dioxide, COOLING of water, SEA ice, OCEAN, ARCTIC climate, AUTUMN
Abstract

As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of Arctic Ocean sea‐air CO2 fluxes and their uncertainties from surface ocean pCO2‐observation products, ocean biogeochemical hindcast and data assimilation models, and atmospheric inversions. For the period of 1985–2018, the Arctic Ocean was a net sink of CO2 of 116 ± 4 TgC yr−1 in the pCO2 products, 92 ± 30 TgC yr−1 in the models, and 91 ± 21 TgC yr−1 in the atmospheric inversions. The CO2 uptake peaks in late summer and early autumn, and is low in winter when sea ice inhibits sea‐air fluxes. The long‐term mean CO2 uptake in the Arctic Ocean is primarily caused by steady‐state fluxes of natural carbon (70% ± 15%), and enhanced by the atmospheric CO2 increase (19% ± 5%) and climate change (11% ± 18%). The annual mean CO2 uptake increased from 1985 to 2018 at a rate of 31 ± 13 TgC yr−1 dec−1 in the pCO2 products, 10 ± 4 TgC yr−1 dec−1 in the models, and 32 ± 16 TgC yr−1 dec−1 in the atmospheric inversions. Moreover, 77% ± 38% of the trend in the net CO2 uptake over time is caused by climate change, primarily due to rapid sea ice loss in recent years. Furthermore, true uncertainties may be larger than the given ensemble standard deviations due to common structural biases across all individual estimates. Plain Language Summary: The Arctic Ocean is at present a net sink for atmospheric CO2 mainly due to the intense cooling of the inflowing waters from the Atlantic and the Pacific. Global warming is amplified in the Arctic Ocean and it experiences a rapid retreat of sea ice. Here, we present synthesized estimates of the Arctic Ocean CO2 uptake and their uncertainties from estimates obtained using different methods. Almost all estimates suggest that the Arctic Ocean was a net sink of CO2 from 1985 to 2018. The CO2 uptake is strong in late summer and early autumn and weak in winter, corresponding to the seasonal variation of sea ice. CO2 uptake has increased in recent years, especially in regions that have experienced sea ice loss. Compared to the global ocean, the Arctic Ocean is unique because climate change, in particular the change in sea ice cover, has enhanced the ocean CO2 uptake almost as much as the increase in atmospheric CO2 over the past 34 years. Moreover, this climate effect on the Arctic Ocean CO2 uptake has become more important in recent years and is the current main driver for the trend toward an increasing CO2 uptake in the Arctic Ocean. Key Points: The Arctic Ocean is estimated to be a net sink of CO2 of 116 ± 4 TgC yr−1 in pCO2 products and 92 ± 30 TgC yr−1 in ocean modelsThe Arctic Ocean CO2 uptake is explained by a steady‐state natural flux (70%) with atmospheric CO2 increase (19%) and climate change (11%)The CO2 uptake increased (31 ± 13 TgC yr−1 dec−1 in products and 10 ± 4 TgC yr−1 dec−1 in models) mostly by decreasing sea ice [ABSTRACT FROM AUTHOR]

Published
2023
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16. Simulated decadal variations of phytoplankton concentration anomalies in the upstream Kuroshio Extension region with a focus on subsurface maxima

Author

Tozuka, Tomoki, Sasai, Yoshikazu, Yasunaka, Sayaka, Sasaki, Hideharu, and Nonaka, Masami

Abstract

Decadal variations of phytoplankton concentrations in the upstream Kuroshio Extension (KE) region are investigated using outputs from a simple ecosystem model embedded in an eddy-resolving ocean general circulation model, which can well simulate decadal modulations of the KE between stable and unstable states. During the KE stable states, surface phytoplankton concentrations are anomalously suppressed (enhanced) to the south (north) of the KE front. Although the surface phytoplankton concentration anomalies are prominent only during winter to spring as revealed by past studies, it is shown for the first time that significant subsurface anomalies centered around 60 m depth persist even in summer and autumn. Further analyses of nitrogen concentration anomalies suggest that the vertical movement of the isopycnal surfaces, vertical mixing of nutrients, and meridional shifts in the KE jet contribute to the anomalous phytoplankton biomass. Moreover, the remarkable subsurface anomalies in phytoplankton concentration may feedback on to decadal sea surface temperature anomalies by modulating absorption of penetrative shortwave radiation., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023

19. Biological organic carbon export estimated from the annual carbon budget observed in the surface waters of the western subarctic and subtropical North Pacific Ocean from 2004 to 2013

Author

Wakita, Masahide, Honda, Makio C., Matsumoto, Kazuhiko, Fujiki, Tetsuichi, Kawakami, Hajime, Yasunaka, Sayaka, Sasai, Yoshikazu, Sukigara, Chiho, Uchimiya, Mario, Kitamura, Minoru, Kobari, Toru, Mino, Yoshihisa, Nagano, Akira, Watanabe, Shuichi, and Saino, Toshiro

Published
2016
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20. Global distribution and variability of subsurface chlorophyll a concentrations

Author

Yasunaka, Sayaka, Ono, Tsuneo, Sasaoka, Kosei, Sato, Kanako, Yasunaka, Sayaka, Ono, Tsuneo, Sasaoka, Kosei, and Sato, Kanako

Abstract

Chlorophyll a (Chl a) often exhibits a maximum concentration in the subsurface layer rather that at the surface. The depth of the Chl a maximum primarily depends on the balance between light penetration from the surface and the nutrient supply from the deep ocean. However, a global map of subsurface Chl a concentrations based on observations has not been presented yet. In this study, we integrate Chl a concentration data from recent biogeochemical floats and historical ship-based (and other) observations and present global maps of subsurface Chl a concentrations with related variables. The subsurface Chl a maximum was observed globally throughout the oceans: at depths greater than 80m in the subtropics and tropics (30 degrees S to 30 degrees N); in the 40-80m depth range in the tropics, in the Southern Ocean (south of 40 degrees S), and at the midlatitudes (30-40 degrees N/S) in the North Pacific; and at depths of less than 40m in the northern subarctic (north of 40 degrees N). The observed maxima all lie below the mixed-layer depth for the entire year in the subtropics and tropics and during summer in the midlatitudes and the northern subarctic. The depths of the subsurface Chl a maxima are greater than those of the photosynthetically active layer in the subtropics but shallower in the tropics and midlatitudes. In the subtropics, a seasonal increase in oxygen below the mixed layer implies substantial new biological production, which corresponds to 10% of the net primary production in that region. During El Nino, subsurface Chl a concentrations are higher in the middle and eastern equatorial Pacific but lower to the west in comparison with La Nina, a pattern which is opposite to that on the surface. The spatiotemporal variability of the Chl a concentrations described here has implications to not only for the biogeochemical cycling in the ocean but also for understanding the thermal structure and dynamics of the ocean via absorption of shortwave radiation.

Published
2022
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21. Overview: Recent advances in the understanding of the northern Eurasian environments and of the urban air quality in China – a Pan-Eurasian Experiment (PEEX) programme perspective

Author

Lappalainen, Hanna K., primary, Petäjä, Tuukka, additional, Vihma, Timo, additional, Räisänen, Jouni, additional, Baklanov, Alexander, additional, Chalov, Sergey, additional, Esau, Igor, additional, Ezhova, Ekaterina, additional, Leppäranta, Matti, additional, Pozdnyakov, Dmitry, additional, Pumpanen, Jukka, additional, Andreae, Meinrat O., additional, Arshinov, Mikhail, additional, Asmi, Eija, additional, Bai, Jianhui, additional, Bashmachnikov, Igor, additional, Belan, Boris, additional, Bianchi, Federico, additional, Biskaborn, Boris, additional, Boy, Michael, additional, Bäck, Jaana, additional, Cheng, Bin, additional, Chubarova, Natalia, additional, Duplissy, Jonathan, additional, Dyukarev, Egor, additional, Eleftheriadis, Konstantinos, additional, Forsius, Martin, additional, Heimann, Martin, additional, Juhola, Sirkku, additional, Konovalov, Vladimir, additional, Konovalov, Igor, additional, Konstantinov, Pavel, additional, Köster, Kajar, additional, Lapshina, Elena, additional, Lintunen, Anna, additional, Mahura, Alexander, additional, Makkonen, Risto, additional, Malkhazova, Svetlana, additional, Mammarella, Ivan, additional, Mammola, Stefano, additional, Buenrostro Mazon, Stephany, additional, Meinander, Outi, additional, Mikhailov, Eugene, additional, Miles, Victoria, additional, Myslenkov, Stanislav, additional, Orlov, Dmitry, additional, Paris, Jean-Daniel, additional, Pirazzini, Roberta, additional, Popovicheva, Olga, additional, Pulliainen, Jouni, additional, Rautiainen, Kimmo, additional, Sachs, Torsten, additional, Shevchenko, Vladimir, additional, Skorokhod, Andrey, additional, Stohl, Andreas, additional, Suhonen, Elli, additional, Thomson, Erik S., additional, Tsidilina, Marina, additional, Tynkkynen, Veli-Pekka, additional, Uotila, Petteri, additional, Virkkula, Aki, additional, Voropay, Nadezhda, additional, Wolf, Tobias, additional, Yasunaka, Sayaka, additional, Zhang, Jiahua, additional, Qiu, Yubao, additional, Ding, Aijun, additional, Guo, Huadong, additional, Bondur, Valery, additional, Kasimov, Nikolay, additional, Zilitinkevich, Sergej, additional, Kerminen, Veli-Matti, additional, and Kulmala, Markku, additional

Published
2022
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32. Overview: Recent advances on the understanding of the Northern Eurasian environments and of the urban air quality in China - Pan Eurasian Experiment (PEEX) program perspective

Author

Lappalainen, Hanna, primary, Petäjä, Tuukka, additional, Vihma, Timo, additional, Räisänen, Jouni, additional, Baklanov, Alexander, additional, Chalov, Sergey, additional, Esau, Igor, additional, Ezhova, Ekaterina, additional, Leppäranta, Matti, additional, Pozdnyakov, Dmitry, additional, Pumpanen, Jukka, additional, Andreae, Meinrat O., additional, Arshinov, Michael, additional, Asmi, Eija, additional, Bai, Jianhui, additional, Bashmachnikov, Igor, additional, Belan, Boris, additional, Bianchi, Federico, additional, Biskaborn, Boris, additional, Boy, Michael, additional, Bäck, Jaana, additional, Cheng, Bin, additional, Chubarova, Natalia Ye, additional, Duplissy, Jonathan, additional, Dyukarev, Egor, additional, Eleftheriadis, Konstantinos, additional, Forsius, Martin, additional, Heimann, Martin, additional, Juhola, Sirkku, additional, Konovalov, Vladimir, additional, Konovalov, Igor, additional, Konstantinov, Pavel, additional, Koster, Kajar, additional, Lapsina, Elena, additional, Lintunen, Anna, additional, Mahura, Alexander, additional, Makkonen, Risto, additional, Malkhazova, Svetlana, additional, Mammarella, Ivan, additional, Mammola, Stefano, additional, Mazon, Stephany, additional, Meinander, Outi, additional, Mikhailov, Eugene, additional, Miles, Victoria, additional, Myslenko, Stanislav, additional, Orlov, Dimitry, additional, Paris, Jean-Daniel, additional, Pirazzini, Robertta, additional, Popovicheva, Olga, additional, Pulliainen, Jouni, additional, Rautiainen, Kimmo, additional, Sachs, Torsten, additional, Shevchenko, Vladimir, additional, Skorokhod, Andrey, additional, Stohl, Andreas, additional, Suhonen, Elli, additional, Thomson, Erik S., additional, Tsidilina, Marina, additional, Tynkkynen, Veli-Pekka, additional, Uotila, Petteri, additional, Virkkula, Aki, additional, Voropay, Nadezhda, additional, Wolf, Tobias, additional, Yasunaka, Sayaka, additional, Zhang, Jiahua, additional, Qui, Yubao, additional, Ding, Aijun, additional, Guo, Huadong, additional, Bondur, Valery, additional, Kasimov, Nikolay, additional, Zilitinkevich, Sergey, additional, Kerminen, Veli-Matti, additional, and Kulmala, Markku, additional

Published
2021
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34. Second Report of TPOS 2020

Author

Kessler, William S., Wijffels, Susan, Cravatte, Sophie, Smith, Neville, Fujii, Yosuke, Large, William G., Takaya, Yuhei, Hendon, Harry, Penny, Stephen G., Sutton, Adrienne J., Strutton, Peter, Feely, Richard, Kouketsu, Shinya, Yasunaka, Sayaka, Serra, Yolande, Dewitte, Boris, Takahashi, Ken, Xue, Yan, Montes, Ivonne, Clayson, Carol Anne, Cronin, Meghan F., Farrar, Tom, Lee, Tong, Mcgregor, Shayne, Xiangzhou Song, Sprintall, Janet, Wittenberg, Andrew T., Weidong Yu, Ando, Kentaro, Gasparin, Florent, Roemmich, Dean, Masich, Jessica, O'Brien, Kevin, Legler, David, Ueki, Iwao, E. Robert Kursinski, Hill, Katherine, Cobb, Kim M., O'Neill, Larry, Upchurch, Lucia, and Brunner, Shelby

Published
2019
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35. Addressing Arctic Challenges Requires a Synoptic Ocean Survey

Author

Paasche, Øyvind, Olsen, Are, Årthun, Marius, Anderson, Leif, Wängberg, Sten-Åke, Ashjian, Carin, Grebmeier, Jacqueline, Kikuchi, Takashi, Nishino, Shigeto, Yasunaka, Sayaka, Kang, Sung-Ho, Cho, Kyoung-Ho, Azetsu-Scott, Kumiko, Williams, William, Carmack, Eddy, Torres-Valdés, Sinhué, Tyrrell, Toby, Edelvang, Karen, He, Jianfeng, Kassens, Heidi, Paasche, Øyvind, Olsen, Are, Årthun, Marius, Anderson, Leif, Wängberg, Sten-Åke, Ashjian, Carin, Grebmeier, Jacqueline, Kikuchi, Takashi, Nishino, Shigeto, Yasunaka, Sayaka, Kang, Sung-Ho, Cho, Kyoung-Ho, Azetsu-Scott, Kumiko, Williams, William, Carmack, Eddy, Torres-Valdés, Sinhué, Tyrrell, Toby, Edelvang, Karen, He, Jianfeng, and Kassens, Heidi

Published
2019

36. Addressing Arctic Challenges Requires a Synoptic Ocean Survey

Author

Paasche, Oeyvind, Olsen, Are, Aarthun, Marius, Anderson, Leif, Wängberg, Sten-Aake, Ashjian, Carin, Grebmeier, Jacqueline, Kikuchi, Takashi, Nishino, Shigeto, Yasunaka, Sayaka, Kang, Sung-Ho, Cho, Kyoung-Ho, Azetsu-Scott, Kumiko, Williams, William, Carmack, Eddy, Torres-Valdes, Sinhue, Tyrrell, Toby, Edelvang, Karen, He, Jianfeng, Kassens, Heidemarie, Paasche, Oeyvind, Olsen, Are, Aarthun, Marius, Anderson, Leif, Wängberg, Sten-Aake, Ashjian, Carin, Grebmeier, Jacqueline, Kikuchi, Takashi, Nishino, Shigeto, Yasunaka, Sayaka, Kang, Sung-Ho, Cho, Kyoung-Ho, Azetsu-Scott, Kumiko, Williams, William, Carmack, Eddy, Torres-Valdes, Sinhue, Tyrrell, Toby, Edelvang, Karen, He, Jianfeng, and Kassens, Heidemarie

Abstract

A coordinated effort involving trailblazing science — and icebreaking ships — from many nations is needed to fill gaps in our understanding of the Arctic Ocean and how it’s changing.

Published
2019
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37. Quantitative Assessment of Factors Contributing to Variations in Sea Surface pCO2in the Pacific Sector of the Arctic Ocean

Author

Tozawa, Manami, Nomura, Daiki, Matsuura, Mirai, Hatta, Mariko, Fujiwara, Amane, Yasunaka, Sayaka, and Murata, Akihiko

Abstract

To quantitatively assess seasonal variations in the partial pressure of carbon dioxide (pCO2) in the Pacific sector of the Arctic Ocean (Canada Basin and Chukchi Sea) in 2021, water temperature, salinity, chlorophyll‐a, pCO2, dissolved inorganic carbon (DIC), total alkalinity (TA), and nutrients were measured. During summer 2021, surface water pCO2in our study area (315 ± 41 μatm) was undersaturated with respect to the atmosphere (404 ± 4 μatm), and the ocean was a sink for atmospheric CO2(−10.5 ± 11.0 mmol C m−2day−1). Using DIC, TA, and nutrients in the temperature minimum layer, we estimated the under‐ice pCO2in the water during the previous winter and calculated changes in pCO2(δpCO2) due to temperature changes, freshwater inflow, biological activity, and other factors (gas exchange and advection) from winter to summer. In the Chukchi Sea, biological activity and temperature changes had significant impacts on pCO2, whereas in the Canada Basin, the influx of freshwater caused a significant decrease in pCO2. Our results suggested that different types of freshwaters had different effects on pCO2, with sea ice meltwater having a greater effect on reducing pCO2than river water or snowmelt water. We therefore emphasize the importance of freshwater type and proportion, as well as freshwater supply, for prediction of future pCO2changes. Assessment of the factors that cause ocean CO2to vary is important in the Arctic Ocean, which acts as an atmospheric CO2sink that will change significantly because of global warming. Seawater and sea ice samples were collected in the Pacific sector of the Arctic Ocean to investigate the carbonate chemistry. The partial pressure of carbon dioxide (pCO2) was lower on the sea surface than in the atmosphere during summer, and the ocean absorbed atmospheric CO2. The decreases of pCO2from winter to summer were driven primarily by biological activity in the Chukchi Sea (partially offset by temperature increases) and by freshwater additions in the Canada Basin. Sea ice meltwater, snow meltwater, and river water had different effects on pCO2, even though all of them diluted the carbonate concentrations of surface water, because of differences in the alkalinity and carbonate chemistry among these freshwater sources. The Pacific sector of the Arctic Ocean absorbed atmospheric CO2in summerIn the Chukchi Sea, biological activity and temperature changed pCO2, while in the Canada Basin, the freshwater caused a decrease in pCO2Sea ice meltwater had a greater effect on reducing pCO2than river water or snow meltwater The Pacific sector of the Arctic Ocean absorbed atmospheric CO2in summer In the Chukchi Sea, biological activity and temperature changed pCO2, while in the Canada Basin, the freshwater caused a decrease in pCO2 Sea ice meltwater had a greater effect on reducing pCO2than river water or snow meltwater

Published
2024
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38. Arctic Ocean CO2 uptake: An improved multiyear estimate of the air-sea CO2 flux incorporating chlorophyll a concentrations

Author

Yasunaka, Sayaka, Siswanto, Eko, Olsen, Are, Hoppema, Mario, Watanabe, Eiji, Fransson, Agneta, Chierici, Melissa, Murata, Akihiko, Lauvset, Siv K., Wanninkhof, Rik, Takahashi, Taro, Kosugi, Naohiro, Omar, Abdirahman M., Heuven, Steven, Mathis, Jeremy T., and Isotope Research

Subjects
CARBON-DIOXIDE, TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES, NEURAL-NETWORK, WIND-SPEED, PHYTOPLANKTON BLOOMS, COCCOLITHOPHORE BLOOMS, UPTAKE CAPACITY, INTERANNUAL VARIABILITY, GLOBAL OCEAN, NORTH-ATLANTIC, GAS-EXCHANGE
Abstract

We estimated monthly air–sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of 60∘ N from 1997 to 2014. This was done by 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. We applied new algorithms for extracting Chl a from satellite remote sensing reflectance with close examination of uncertainty of the obtained Chl a values. The overall relationship between pCO2w and Chl a was negative, whereas the relationship varied among seasons and regions. The addition of Chl a as a parameter in the SOM process enabled us to improve the estimate of pCO2w, particularly via better representation of its decline in spring, which resulted from biologically mediated pCO2w reduction. As a result of the inclusion of Chl a, the uncertainty in the CO2 flux estimate was reduced, with a net annual Arctic Ocean CO2 uptake of 180 ± 130 Tg C yr−1. Seasonal to interannual variation in the CO2 influx was also calculated.

Published
2018

39. Addressing Arctic Challenges Requires a Synoptic Ocean Survey

Author

Paasche, �yvind, primary, Olsen, Are, additional, �rthun, Marius, additional, Anderson, Leif, additional, W�ngberg, Sten-�ke, additional, Ashjian, Carin, additional, Grebmeier, Jacqueline, additional, Kikuchi, Takashi, additional, Nishino, Shigeto, additional, Yasunaka, Sayaka, additional, Kang, Sung-Ho, additional, Cho, Kyoung-Ho, additional, Azetsu-Scott, Kumiko, additional, Williams, William, additional, Carmack, Eddy, additional, Torres-Vald�s, Sinhu�, additional, Tyrrell, Toby, additional, Edelvang, Karen, additional, He, Jianfeng, additional, and Kassens, Heidi, additional

Published
2019
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41. Arctic Ocean CO<sub>2</sub> uptake: an improved multiyear estimate of the air–sea CO<sub>2</sub> flux incorporating chlorophyll <i>a</i> concentrations

Author

Yasunaka, Sayaka, primary, Siswanto, Eko, additional, Olsen, Are, additional, Hoppema, Mario, additional, Watanabe, Eiji, additional, Fransson, Agneta, additional, Chierici, Melissa, additional, Murata, Akihiko, additional, Lauvset, Siv K., additional, Wanninkhof, Rik, additional, Takahashi, Taro, additional, Kosugi, Naohiro, additional, Omar, Abdirahman M., additional, van Heuven, Steven, additional, and Mathis, Jeremy T., additional

Published
2018
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42. Arctic Ocean CO2 uptake: an improved multi-year estimate of the air–sea CO2 flux incorporating chlorophyll-a concentrations

Author

Yasunaka, Sayaka, Siswanto, Eko, Olsen, Are, Hoppema, Mario, Watanabe, Eiji, Fransson, Agneta, Chierici, Melissa, Murata, Akihiko, Lauvset, Siv K., Wanninkhof, Rik, Takahashi, Taro, Kosugi, Naohiro, Omar, Abdirahman M., van Heuven, Steven, Mathis, Jeremy T., Yasunaka, Sayaka, Siswanto, Eko, Olsen, Are, Hoppema, Mario, Watanabe, Eiji, Fransson, Agneta, Chierici, Melissa, Murata, Akihiko, Lauvset, Siv K., Wanninkhof, Rik, Takahashi, Taro, Kosugi, Naohiro, Omar, Abdirahman M., van Heuven, Steven, and Mathis, Jeremy T.

Published
2017

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

Author

Yasunaka, Sayaka, primary, Siswanto, Eko, additional, Olsen, Are, additional, Hoppema, Mario, additional, Watanabe, Eiji, additional, Fransson, Agneta, additional, Chierici, Melissa, additional, Murata, Akihiko, additional, Lauvset, Siv K., additional, Wanninkhof, Rik, additional, Takahashi, Taro, additional, Kosugi, Naohiro, additional, Omar, Abdirahman M., additional, van Heuven, Steven, additional, and Mathis, Jeremy T., additional

Published
2017
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44. Mapping of the air–sea CO2 flux in the Arctic Ocean and its adjacent seas: Basin-wide distribution and seasonal to interannual variability

Author

Yasunaka, Sayaka, Murata, Akihiko, Watanabe, Eiji, Chierici, Melissa, Fransson, Agneta, van Heuven, Steven, Hoppema, Mario, Ishii, Masao, Johannessen, Truls, Kosugi, Naohiro, Lauvset, Siv K., Mathis, Jeremy T., Nishino, Shigeto, Omar, Abdirahman M., Olsen, Are, Sasano, Daisuke, Takahashi, Taro, Wanninkhof, Rik, Yasunaka, Sayaka, Murata, Akihiko, Watanabe, Eiji, Chierici, Melissa, Fransson, Agneta, van Heuven, Steven, Hoppema, Mario, Ishii, Masao, Johannessen, Truls, Kosugi, Naohiro, Lauvset, Siv K., Mathis, Jeremy T., Nishino, Shigeto, Omar, Abdirahman M., Olsen, Are, Sasano, Daisuke, Takahashi, Taro, and Wanninkhof, Rik

Published
2016

47. Mapping of the air–sea CO2 flux in the Arctic Ocean and its adjacent seas: Basin-wide distribution and seasonal to interannual variability

Author

Yasunaka, Sayaka, primary, Murata, Akihiko, additional, Watanabe, Eiji, additional, Chierici, Melissa, additional, Fransson, Agneta, additional, van Heuven, Steven, additional, Hoppema, Mario, additional, Ishii, Masao, additional, Johannessen, Truls, additional, Kosugi, Naohiro, additional, Lauvset, Siv K., additional, Mathis, Jeremy T., additional, Nishino, Shigeto, additional, Omar, Abdirahman M., additional, Olsen, Are, additional, Sasano, Daisuke, additional, Takahashi, Taro, additional, and Wanninkhof, Rik, additional

Published
2016
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48. Arctic Ocean CO2 uptake: an improved multiyear estimate of the air-sea CO2 flux incorporating chlorophyll a concentrations.

Author

Yasunaka, Sayaka, Siswanto, Eko, Olsen, Are, Hoppema, Mario, Watanabe, Eiji, Fransson, Agneta, Chierici, Melissa, Murata, Akihiko, Lauvset, Siv K., Wanninkhof, Rik, Takahashi, Taro, Kosugi, Naohiro, Omar, Abdirahman M., van Heuven, Steven, and Mathis, Jeremy T.

Subjects
CARBON dioxide in seawater, CHLOROPHYLL content of seawater, SELF-organizing maps, COMPUTER algorithms, MARINE ecology
Abstract

We estimated monthly air-sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of 60° N from 1997 to 2014. This was done by 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. We applied new algorithms for extracting Chl a from satellite remote sensing reflectance with close examination of uncertainty of the obtained Chl a values. The overall relationship between pCO2w and Chl a was negative, whereas the relationship varied among seasons and regions. The addition of Chl a as a parameter in the SOM process enabled us to improve the estimate of pCO2w, particularly via better representation of its decline in spring, which resulted from biologically mediated pCO2w reduction. As a result of the inclusion of Chl a, the uncertainty in the CO2 flux estimate was reduced, with a net annual Arctic Ocean CO2 uptake of 180±130 TgCyr-1. Seasonal to interannual variation in the CO2 influx was also calculated. [ABSTRACT FROM AUTHOR]

Published
2018
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49. Basin-scale distribution of NH and NO in the Pacific Ocean.

Author

Yasunaka, Sayaka, Nojiri, Yukihiro, Hashioka, Taketo, Yoshikawa, Chisato, Kodama, Taketoshi, Nakaoka, Shin-ichiro, Chiba, Sanae, Hashihama, Fuminori, Wakita, Masahide, Furuya, Ken, Sasano, Daisuke, Murata, Akihiko, Uchida, Hiroshi, and Aoyama, Michio

Subjects
UPWELLING (Oceanography), NUTRIENT cycles, OCEAN circulation, SEASONAL temperature variations, OCEANOGRAPHY
Abstract

We used more than 25,000 nutrient samples to elucidate for the first time basin-scale distributions and seasonal changes of surface ammonium (NH ) and nitrite (NO ) concentrations in the Pacific Ocean. The highest NH , NO , and nitrate (NO ) concentrations were observed north of 40°N, in the coastal upwelling region off the coast of Mexico, and in the Tasman Sea. NH concentrations were elevated during May-October in the western subarctic North Pacific, May-December in the eastern subarctic North Pacific, and June-September in the subtropical South Pacific. NO concentrations were highest in winter in both hemispheres. The seasonal cycle of NH was synchronous with NO , NO , and satellite chlorophyll a concentrations in the western subtropical South Pacific, whereas it was synchronous with chlorophyll- a but out of phase with NO and NO in the subarctic regions. [ABSTRACT FROM AUTHOR]

Published
2018
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50. An Assessment of CO2Uptake in the Arctic Ocean From 1985 to 2018

Author

Yasunaka, Sayaka, Manizza, Manfredi, Terhaar, Jens, Olsen, Are, Yamaguchi, Ryohei, Landschützer, Peter, Watanabe, Eiji, Carroll, Dustin, Adiwira, Hanani, Müller, Jens Daniel, and Hauck, Judith

Abstract

As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of Arctic Ocean sea‐air CO2fluxes and their uncertainties from surface ocean pCO2‐observation products, ocean biogeochemical hindcast and data assimilation models, and atmospheric inversions. For the period of 1985–2018, the Arctic Ocean was a net sink of CO2of 116 ± 4 TgC yr−1in the pCO2products, 92 ± 30 TgC yr−1in the models, and 91 ± 21 TgC yr−1in the atmospheric inversions. The CO2uptake peaks in late summer and early autumn, and is low in winter when sea ice inhibits sea‐air fluxes. The long‐term mean CO2uptake in the Arctic Ocean is primarily caused by steady‐state fluxes of natural carbon (70% ± 15%), and enhanced by the atmospheric CO2increase (19% ± 5%) and climate change (11% ± 18%). The annual mean CO2uptake increased from 1985 to 2018 at a rate of 31 ± 13 TgC yr−1dec−1in the pCO2products, 10 ± 4 TgC yr−1dec−1in the models, and 32 ± 16 TgC yr−1dec−1in the atmospheric inversions. Moreover, 77% ± 38% of the trend in the net CO2uptake over time is caused by climate change, primarily due to rapid sea ice loss in recent years. Furthermore, true uncertainties may be larger than the given ensemble standard deviations due to common structural biases across all individual estimates. The Arctic Ocean is at present a net sink for atmospheric CO2mainly due to the intense cooling of the inflowing waters from the Atlantic and the Pacific. Global warming is amplified in the Arctic Ocean and it experiences a rapid retreat of sea ice. Here, we present synthesized estimates of the Arctic Ocean CO2uptake and their uncertainties from estimates obtained using different methods. Almost all estimates suggest that the Arctic Ocean was a net sink of CO2from 1985 to 2018. The CO2uptake is strong in late summer and early autumn and weak in winter, corresponding to the seasonal variation of sea ice. CO2uptake has increased in recent years, especially in regions that have experienced sea ice loss. Compared to the global ocean, the Arctic Ocean is unique because climate change, in particular the change in sea ice cover, has enhanced the ocean CO2uptake almost as much as the increase in atmospheric CO2over the past 34 years. Moreover, this climate effect on the Arctic Ocean CO2uptake has become more important in recent years and is the current main driver for the trend toward an increasing CO2uptake in the Arctic Ocean. The Arctic Ocean is estimated to be a net sink of CO2of 116 ± 4 TgC yr−1in pCO2products and 92 ± 30 TgC yr−1in ocean modelsThe Arctic Ocean CO2uptake is explained by a steady‐state natural flux (70%) with atmospheric CO2increase (19%) and climate change (11%)The CO2uptake increased (31 ± 13 TgC yr−1dec−1in products and 10 ± 4 TgC yr−1dec−1in models) mostly by decreasing sea ice The Arctic Ocean is estimated to be a net sink of CO2of 116 ± 4 TgC yr−1in pCO2products and 92 ± 30 TgC yr−1in ocean models The Arctic Ocean CO2uptake is explained by a steady‐state natural flux (70%) with atmospheric CO2increase (19%) and climate change (11%) The CO2uptake increased (31 ± 13 TgC yr−1dec−1in products and 10 ± 4 TgC yr−1dec−1in models) mostly by decreasing sea ice

Published
2023
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