Browsing by Author "Cai, Wei-Jun"
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Item A multi-decade record of high-quality fCO(2) data in version 3 of the Surface Ocean CO2 Atlas (SOCAT)(Copernicus Gesellschaft MBH, 9/15/16) Bakker,Dorothee C. E.; Pfeil,Benjamin; Landa,Camilla S.; Metzl,Nicolas; O'Brien,Kevin M.; Olsen,Are; Smith,Karl; Cosca,Cathy; Harasawa,Sumiko; Jones,Stephen D.; Nakaoka,Shin-ichiro; Nojiri,Yukihiro; Schuster,Ute; Steinhoff,Tobias; Sweeney,Colm; Takahashi,Taro; Tilbrook,Bronte; Wada,Chisato; Wanninkhof,Rik; Alin,Simone R.; Balestrini,Carlos F.; Barbero,Leticia; Bates,Nicholas R.; Bianchi,Alejandro A.; Bonou,Frederic; Boutin,Jacqueline; Bozec,Yann; Burger,Eugene F.; Cai,Wei-Jun; Castle,Robert D.; Chen,Liqi; Chierici,Melissa; Currie,Kim; Evans,Wiley; Featherstone,Charles; Feely,Richard A.; Fransson,Agneta; Goyet,Catherine; Greenwood,Naomi; Gregor,Luke; Hankin,Steven; Hardman-Mountford,Nick J.; Harlay,Jerome; Hauck,Judith; Hoppema,Mario; Humphreys,Matthew P.; Hunt,ChristopherW; Huss,Betty; Ibanhez,J. Severino P.; Johannessen,Truls; Keeling,Ralph; Kitidis,Vassilis; Koertzinger,Arne; Kozyr,Alex; Krasakopoulou,Evangelia; Kuwata,Akira; Landschuetzer,Peter; Lauvset,Siv K.; Lefevre,Nathalie; Lo Monaco,Claire; Manke,Ansley; Mathis,Jeremy T.; Merlivat,Liliane; Millero,Frank J.; Monteiro,Pedro M. S.; Munro,David R.; Murata,Akihiko; Newberger,Timothy; Omar,Abdirahman M.; Ono,Tsuneo; Paterson,Kristina; Pearce,David; Pierrot,Denis; Robbins,Lisa L.; Saito,Shu; Salisbury,Joe; Schlitzer,Reiner; Schneider,Bernd; Schweitzer,Roland; Sieger,Rainer; Skjelvan,Ingunn; Sullivan,Kevin F.; Sutherland,Stewart C.; Sutton,Adrienne J.; Tadokoro,Kazuaki; Telszewski,Maciej; Tuma,Matthias; van Heuven,Steven M. A. C.; Vandemark,Doug; Ward,Brian; Watson,Andrew J.; Xu,Suqing; Dorothee C. E. Bakker, Benjamin Pfeil, Camilla S. Landa, Nicolas Metzl, Kevin M. OBrien,Are Olsen, Karl Smith, Cathy Cosca, Sumiko Harasawa, Stephen D. Jones,Shin-ichiro Nakaoka, Yukihiro Nojiri, Ute Schuster, Tobias Steinhoff, Colm Sweeney, Taro Takahashi, Bronte Tilbrook, Chisato Wada, Rik Wanninkhof, Simone R. Alin,Carlos F. Balestrini, Leticia Barbero, Nicholas R. Bates, Alejandro A. Bianchi,Fr_d_ric Bonou, Jacqueline Boutin, Yann Bozec21, Eugene F. Burger5, Wei-Jun Cai,Robert D. Castle, Liqi Chen, Melissa Chierici, Kim Currie, Wiley Evans, Charles Featherstone, Richard A. Feely, Agneta Fransson, Catherine Goyet,Naomi Greenwood, Luke Gregor, Steven Hankin, Nick J. Hardman-Mountford, J_rome Harlay, Judith Hauck, Mario Hoppema, Matthew P. Humphreys,ChristopherW. Hunt, Betty Huss, J. Severino P. Ibanhez, Truls Johannessen, Ralph Keeling, Vassilis Kitidis, Arne K_rtzinger, Alex Kozyr, Evangelia Krasakopoulou,Akira Kuwata, Peter Landschuetzer, Siv K. Lauvset, Nathalie Lefevre, Claire Lo Monaco,Ansley Manke, Jeremy T. Mathis, Liliane Merlivat, Frank J. Millero, Pedro M. S. Monteiro,David R. Munro, Akihiko Murata, Timothy Newberger, Abdirahman M. Omar,Tsuneo Ono, Kristina Paterson, David Pearce, Denis Pierrot, Lisa L. Robbins, Shu Saito, Joe Salisbury, Reiner Schlitzer, Bernd Schneider, Roland Schweitzer, Rainer Sieger,Ingunn Skjelvan, Kevin F. Sullivan, Stewart C. Sutherland, Adrienne J. Sutton,Kazuaki Tadokoro, Maciej Telszewski, Matthias Tuma, Steven M. A. C. van Heuven,Doug Vandemark, Brian Ward, Andrew J. Watson, and Suqing Xu; Cai, Wei-JunThe Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO(2) (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million fCO(2) values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million fCO(2) values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO(2) values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO(2) has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "living data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014).Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770. The gridded products are available here: doi: 10.3334/CDIAC/OTG.SOCAT_V3_GRID.Item A roadmap for Ocean Negative Carbon Emission eco-engineering in sea-farming fields(The Innovation Geoscience, 2023-09-14) Jiao, Nianzhi; Zhu, Chenba; Liu, Jihua; Luo, Tingwei; Bai, Mindong; Yu, Zhiming; Chen, Quanrui; Rinkevich, Buki; Weinbauer, Markus; Thomas, Helmuth; Fernández-Méndez, Mar; López-Abbate, Celeste; Signori, Camila Negrão; Nagappa, Ramaiah; Koblížek, Michal; Kaartokallio, Hermanni; Hyun, Jung-Ho; Jiao, Fanglue; Chen, Feng; Cai, Wei-JunCarbon neutralization has become a significant, inevitable, and urgent strategy for both adaptation and mitigation of global warming caused by anthropogenic CO2 emissions, and its environmental consequences such as ocean acidification. However, the reduction of anthropogenic CO2 emissions often conflicts with economic development. In contrast, environmentally-friendly negative carbon emissions can be a way of killing two birds with one stone, capturing carbon dioxide and ensuring economic development, and therefore become imperative to achieve carbon-neutral goals.Item Agents of change and temporal nutrient dynamics in the Altamaha River Watershed(Ecological Society of America, 2017-01-23) Takagi, Kimberly K.; Hunter, Kimberley S.; Cai, Wei-Jun; Joye, Samantha B.; Kimberly K. Takagi, Kimberley S. Hunter, Wei-Jun Cai, and Samantha B. Joye; Cai, Wei-JunNutrient and carbon dynamics in river ecosystems are shifting, and climate change is likely a driving factor; however, some previous studies indicate anthropogenic modification of natural resources may supersede the effects of climate. To understand temporal changes in river ecosystems, consideration of how these agents act independently and collectively to affect watershed biogeochemistry is necessary. Through the Georgia Coastal Ecosystems Long-Term Ecological Research Project, we assessed nutrient (phosphorus, nitrogen, silicate) and carbon dynamics, with specific regard to import and export, in the Altamaha River Basin from 2000 to 2012. This is the first study in the region to document the biogeochemical patterns in the Altamaha’s four main tributaries, the Little Ocmulgee, Ocmulgee, Oconee, and Ohoopee rivers, and the relationships between biogeochemistry and historical precipitation and discharge patterns as well as agricultural and population census data. As discharge patterns are a primary driver of nutrient loads, we determined that water use was a dominant factor in the shifting ecosystem dynamics. Dissolved inorganic nitrogen loads were primarily driven by population density and dissolved inorganic phosphorus loads were strongly influenced by livestock biomass. Taken together, we conclude that both the transportation and biogeochemical cycling of nutrients within the Altamaha River Watershed were highly impacted by anthropogenic influences, which were then further exacerbated by continued climate change. Furthermore, the N-and P-loads in the Altamaha River and tributaries were dominated by dissolved organic nitrogen and dissolved organic phosphorus, emphasizing a need to further study the bioavailability of these species and the mechanisms driving their potential ecological impacts.Item And on top of all that…: Coping with ocean acidification in the midst of many stressors(The Oceanography Society., 2015-06-01) Breitburg, Denise L.; Salisbury, Joseph; Bernhard, Joan M.; Cai, Wei-Jun; Dupont, Sam; Doney, Scott C.; Kroeker, Kristy J.; Levin, Lisa A.; Long, Christopher; Milke, Lisa M.; Miller, Seth H.; Phelan, Beth; Passow, Uta; Seibel, Brad A.; Todgham, Anne E.; Tarrant, Ann M.; Denise L. Breitburg, Joseph Salisbury, Joan M. Bernhard, Wei-Jun Cai, Sam Dupont, Scott C. Doney, Kristy J. Kroeker, Lisa A. Levin, W. Christopher Long, Lisa M. Milke, Seth H. Miller, Beth Phelan, Uta Passow, Brad A. Seibel, Anne E. Todgham, and Ann M. Tarrant; Cai, Wei-JunOceanic and coastal waters are acidifying due to processes dominated in the open ocean by increasing atmospheric CO2 and dominated in estuaries and some coastal waters by nutrient-fueled respiration. The patterns and severity of acidification, as well as its effects, are modified by the host of stressors related to human activities that also influence these habitats. Temperature, deoxygenation, and changes in food webs are particularly important co-stressors because they are pervasive, and both their causes and effects are often mechanistically linked to acidification. Development of a theoretical underpinning to multiple stressor research that considers physiological, ecological, and evolutionary perspectives is needed because testing all combinations of stressors and stressor intensities experimentally is impossible. Nevertheless, use of a wide variety of research approaches is a logical and promising strategy for improving understanding of acidification and its effects. Future research that focuses on spatial and temporal patterns of stressor interactions and on identifying mechanisms by which multiple stressors affect individuals, populations, and ecosystems is critical. It is also necessary to incorporate consideration of multiple stressors into management, mitigation, and adaptation to acidification and to increase public and policy recognition of the importance of addressing acidification in the context of the suite of other stressors with which it potentially interacts.Item Carbonate Parameter Estimation and Its Application in Revealing Temporal and Spatial Variation in the South and Mid-Atlantic Bight, USA(Journal of Geophysical Research: Oceans, 2022-06-22) Li, Xinyu; Xu, Yuan-Yuan; Kirchman, David L.; Cai, Wei-JunTo overcome the limitations due to sporadic carbonate parameter data, this study developed and evaluated empirical multiple linear regression (MLR) models for dissolved inorganic carbon (DIC), pH in total scale (pHT), and aragonite carbonate saturation state (ΩAr) using hydrographic data (temperature, salinity, and oxygen) measured during 2007–2018 in the South Atlantic Bight (SAB) and Mid-Atlantic Bight (MAB) along the U.S. East Coast. We first reviewed the assumptions and routines of MLR models and then generated MLR models for each cruise for all three carbonate parameters in each region and assessed model performance. Models derived from measured spectrophotometric pH have smaller uncertainties than pHT models based on pH calculated from total alkalinity (TA) and DIC. The regional differences of carbonate parameters between MAB and SAB are reflected in the coefficients of the empirical models. The MLR model temporal consistency indicates that the effect of the atmospheric CO2 increase on seawater carbonate parameters cannot be unequivocally resolved for the period of this study in the regions. Therefore, we combined different cruises to build composite models for each region. The composite models can capture the key features in the SAB and MAB. To further assess the model applicability, we applied our models to Biogeochemical-Argo data to reconstruct carbonate parameters. The algorithm in this study helps to reconstruct seawater carbonate chemistry using proxy data of high spatial and temporal resolution, which will enhance our understanding of physical and biological processes on carbon cycle and the long-term anthropogenic carbon inputs in coastal oceans. Key Points: - pH estimation models based on measured pH have smaller uncertainties than those based on pH calculated from other carbonate parameters - Models differ between the Mid and South Atlantic Bights, and their temporal changes due to atmospheric CO2 are limited over 10 years - Multiple linear regression models provide a promising tool for reconstructing carbonate parameters using data from autonomous platforms Plain Language Summary: Coastal ocean carbon cycling is a complex process that is influenced by various physical and biological processes. Sporadic carbonate data challenges our understanding of carbon cycling in coastal areas. We first reviewed the assumptions and routines in developing coastal empirical models, and then built linear regression models with frequently measured seawater properties, such as temperature, salinity, and O2, to estimate the carbonate variables along the U.S. East Coast. The key features of seawater carbonate parameters are captured by the empirical models. The sub-regional differences are reflected in the coefficients of the empirical models. We also found that the effect of anthropogenic carbon dioxide increase on the DIC is limited over 10 years. This study helps to reconstruct seawater carbonate chemistry where data are limited, predict future changes in coastal carbonate chemistry, and enhance our understanding of long-term anthropogenic carbon inputs in the coastal ocean.Item The changing CO2 sink in the western Arctic Ocean from 1994 to 2019(Global Biogeochemical Cycles, 2021-12-28) Ouyang, Zhangxian; Li, Yun; Zhong, Wenli; Murata, Akihiko; Nishino, Shigeto; Wu, Yingxu; Jin, Meibing; Kirchman, David; Chen, Liqi; Cai, Wei-JunThe Arctic Ocean has turned from a perennial ice-covered ocean into a seasonally ice-free ocean in recent decades. Such a shift in the air-ice-sea interface has resulted in substantial changes in the Arctic carbon cycle and related biogeochemical processes. To quantitatively evaluate how the oceanic CO2 sink responds to rapid sea ice loss and to provide a mechanistic explanation, here we examined the air-sea CO2 flux and the regional CO2 sink in the western Arctic Ocean from 1994 to 2019 by two complementary approaches: observation-based estimation and a data-driven box model evaluation. The pCO2 observations and model results showed that summer CO2 uptake significantly increased by about 1.4 ± 0.6 Tg C decade−1 in the Chukchi Sea, primarily due to a longer ice-free period, a larger open area, and an increased primary production. However, no statistically significant increase in CO2 sink was found in the Canada Basin and the Beaufort Sea based on both observations and modeled results. The reduced sea ice coverage in summer in the Canada Basin and the enhanced wind speed in the Beaufort Sea potentially promoted CO2 uptake, which was, however, counteracted by a rapidly decreased air-sea pCO2 gradient therein. Therefore, the current and future Arctic Ocean CO2 uptake trends cannot be sufficiently reflected by the air-sea pCO2 gradient alone because of the sea ice variations and other environmental factors.Item Correcting a major error in assessing organic carbon pollution in natural waters(Science Advances, 2021-04-14) Jiao, Nianzhi; Liu, Jihua; Edwards, Bethanie; Lv, Zongqing; Cai, Ruanhong; Liu,Yongqin; Xiao, Xilin; Wang, Jianning; Jiao, Fanglue; Wang, Rui; Huang, Xingyu; Guo, Bixi; Sun, Jia; Zhang, Rui; Zhang, Yao; Tang, Kai; Zheng, Qiang; Azam, Farooq; Batt, John; Cai, Wei-Jun; He, Chen; Herndl, Gerhard J.; Hill, Paul; Hutchins, David; LaRoche, Julie; Lewis, Marlon; MacIntyre, Hugh; Polimene, Luca; Robinson, Carol; Shi, Quan; Suttle, Curtis A.; Thomas, Helmuth; Wallace, Douglas; Legendre, LouisMicrobial degradation of dissolved organic carbon (DOC) in aquatic environments can cause oxygen depletion, water acidification, and CO2 emissions. These problems are caused by labile DOC (LDOC) and not refractory DOC (RDOC) that resists degradation and is thus a carbon sink. For nearly a century, chemical oxygen demand (COD) has been widely used for assessment of organic pollution in aquatic systems. Here, we show through a multicountry survey and experimental studies that COD is not an appropriate proxy of microbial degradability of organic matter because it oxidizes both LDOC and RDOC, and the latter contributes up to 90% of DOC in high-latitude forested areas. Hence, COD measurements do not provide appropriate scientific information on organic pollution in natural waters and can mislead environmental policies. We propose the replacement of the COD method with an optode-based biological oxygen demand method to accurately and efficiently assess organic pollution in natural aquatic environments.Item Impact of Marine Heatwaves on Air-Sea CO2 Flux Along the US East Coast(Geophysical Research Letters, 2024-01-02) Edwing, Kelsea; Wu, Zelun; Lu, Wenfang; Li, Xinyu; Cai, Wei-Jun; Yan, Xiao-HaiMarine heatwaves (MHWs) are extremely warm ocean temperature events that significantly affect marine environments, but their effects on the coastal carbonate system are still uncertain. In this study, we systematically quantify MHWs' impacts on air-sea carbon dioxide (CO2) flux anomalies (FCO2′) in the Mid-Atlantic Bight (MAB) and South Atlantic Bight (SAB) from 1992 to 2020. During the longest MHW in both regions, oceanic CO2 uptake capabilities substantially decreased, primarily due to significant increases in the seawater partial pressure of CO2 (pCO2sea). For all cases, MHWs played a more significant role in driving pCO2sea changes in the MAB than the SAB, where non-thermal drivers dominated pCO2sea variability. In the MAB, weakened wind speeds related to wintertime atmospheric perturbations increase ocean temperatures and pCO2sea, further reducing CO2 uptake during winter MHWs. This work is the first to connect extreme temperatures to coastal air-sea CO2 fluxes. The reduction in CO2 absorption noted during MHWs in this study has important implications for coastal regions to act as continued sinks for excess CO2 emissions in the atmosphere. Key Points - Marine heatwaves (MHWs) primarily generated positive sea surface pCO2 (pCO2sea) anomalies in the Mid-Atlantic Bight (MAB) and South Atlantic Bight (SAB) but had a larger impact on air-sea CO2 flux anomalies in the MAB - Reduced wind speeds amplified MHW contributions during CO2 sink months and counteracted them during CO2 source months - In the MAB, wintertime atmospheric perturbations related to zonal shifts in the jet stream produce slower wind speeds which aid in generating air-sea heat flux type MHW events that ultimately reduce oceanic CO2 uptake Plain Language Summary The transfer of carbon dioxide (CO2) between the atmosphere and ocean is sensitive to sea surface temperature (SST) changes because warmer SSTs increase the sea surface partial pressure of CO2 and reduce the ocean's ability to absorb CO2 from the atmosphere. It is, therefore, conceivable that marine heatwaves (MHWs), which are extremely warm ocean temperature events, could modify how carbon moves between the ocean and the atmosphere. This study provides the first attempt to evaluate the impacts of MHWs on the air-sea CO2 flux (FCO2) anomalies along the US East Coast, encompassing the Mid-Atlantic Bight (MAB) and South Atlantic Bight (SAB) during 1992–2020. Both regions experienced reduced CO2 absorption in response to the longest MHWs in each region. These extreme temperatures had a larger impact on CO2 absorption in the MAB compared to the SAB, where non-temperature factors were more influential. The coastal ocean plays an important role in helping to mitigate human-induced climate change by absorbing excess CO2 from the atmosphere. As such, the demonstrated reduced absorption of the ocean associated with MHWs in this study, which might also apply to other coastal locations, has vital implications for the efficiency of the ocean in offsetting global warming impacts.Item Modeling pCO(2) variability in the Gulf of Mexico(Copernicus Gesellschaft Mbh, 8/8/16) Xue,Zuo; He,Ruoying; Fennel,Katja; Cai,Wei-Jun; Lohrenz,Steven; Huang,Wei-Jen; Tian,Hanqin; Ren,Wei; Zang,Zhengchen; Zuo Xue, Ruoying He, Katja Fennel, Wei-Jun Cai, Steven Lohrenz, Wei-Jen Huang, Hanqin Tian, Wei Ren, and Zhengchen Zang; Cai, Wei-JunA three-dimensional coupled physicalbiogeochemical model was used to simulate and examine temporal and spatial variability of sea surface pCO(2) in the Gulf of Mexico (GoM). The model was driven by realistic atmospheric forcing, open boundary conditions from a data-assimilative global ocean circulation model, and observed freshwater and terrestrial nutrient and carbon input from major rivers. A 7-year model hindcast (2004-2010) was performed and validated against ship measurements. Model results revealed clear seasonality in surface pCO(2) and were used to estimate carbon budgets in the Gulf. Based on the average of model simulations, the GoM was a net CO2 sink with a flux of 1.11 +/- 0.84 x 10(12) mol C yr(-1), which, together with the enormous fluvial inorganic carbon input, was comparable to the inorganic carbon export through the Loop Current. Two model sensitivity experiments were performed: one without biological sources and sinks and the other using river input from the 1904-1910 period as simulated by the Dynamic Land Ecosystem Model (DLEM). It was found that biological uptake was the primary driver making GoM an overall CO2 sink and that the carbon flux in the northern GoM was very susceptible to changes in river forcing. Large uncertainties in model simulations warrant further process-based investigations.Item Projected increase in carbon dioxide drawdown and acidification in large estuaries under climate change(Communications Earth & Environment, 2023-03-13) Li, Ming; Guo, Yijun; Cai, Wei-Jun; Testa, Jeremy M.; Shen, Chunqi; Li, Renjian; Su, JianzhongMost estuaries are substantial sources of carbon dioxide (CO2) to the atmosphere. The estimated estuarine CO2 degassing is about 17% of the total oceanic uptake, but the effect of rising atmospheric CO2 on estuarine carbon balance remains unclear. Here we use 3D hydrodynamic-biogeochemical models of a large eutrophic estuary and a box model of two generic, but contrasting estuaries to generalize how climate change affects estuarine carbonate chemistry and CO2 fluxes. We found that small estuaries with short flushing times remain a CO2 source to the atmosphere, but large estuaries with long flushing times may become a greater carbon sink and acidify. In particular, climate downscaling projections for Chesapeake Bay in the mid-21st century showed a near-doubling of CO2 uptake, a pH decline of 0.1–0.3, and >90% expansion of the acidic volume. Our findings suggest that large eutrophic estuaries will become carbon sinks and suffer from accelerated acidification in a changing climate.Item Rapid changes in the surface carbonate system under complex mixing schemes across the Bering Sea: a comparative study of a forward voyage in July and a return voyage in September 2018(Frontiers in Marine Science, 2023-05-02) Yang, Wei; Wu, Yingxu; Cai, Wei-Jun; Ouyang, Zhangxian; Zhuang, Yanpei; Chen, Liqi; Qi, DiRegulated by the rapid changes in temperature, mixing, and biological production during warm seasons, the surface carbonate system in the Bering Sea is subject to significant spatial-temporal variability. However, the seasonal evolution of the carbon cycle and its controls are less clear due to the lack of observations. Here, we present the carbonate data collected during a forward voyage in July and a return voyage in September 2018 across the Bering Sea. For both voyages, we show distinct dissolved inorganic carbon versus total alkalinity (DIC-TA) relationships and partial pressure of CO2 (pCO2) distribution patterns in the Southern Basin (54-57°N), the Northern Basin (57-59°N), the Slope (59-61°N), the Shelf (61-64°N), and the Bering Strait (>64°N). In the Southern Basin, the Northern Basin, and the Slope, surface water was a two end-member mixing of Rainwater and Bering Summer Water (BSW) during the forward voyage and a two end-member mixing of North Pacific Surface Water (NPSW) and BSW during the return voyage. As a result, the observed DIC was almost consistent with the conservative mixing line, with a slight DIC addition/removal of -8.6~5.8 µmol kg-1, suggesting low biological production/respiration during both voyages. Seasonally, the higher factions of NPSW featuring low pCO2 during the return voyage dominated the pCO2 drawdown from July to September in the Southern Basin and the Slope. On the Shelf, the surface water was a two end-member mixing of plume water from the Anadyr River and BSW during both voyages, but the decreased DIC consumption via biological production from 59.9 ± 25.8 µmol kg-1 to 34.8 ± 14.0 µmol kg-1 contributed to the pCO2 increase from July to September. In the Bering Strait, the coastal area was characterized by the influence of plume water from the Anadyr River in July and the coastal upwelling in September. The high biological production in plume water made a strong CO2 sink during the forward voyage, while the upwelling of carbon-enriched subsurface water with minor DIC consumption made the coastal ecosystem a strong CO2 source during the return voyage. In different geographical regions, the observed seawater pCO2 was much lower than the overlying atmospheric CO2, resulting in a net CO2 sink with fluxes of -2.1~-14.0 mmol m-2 d-1 and -2.5~-11.6 mmol m-2 d-1, respectively, during the forward and return voyages. Highlights 1. The mixing of NPSW featuring low pCO2 dominated the pCO2 drawdown from July to September in the Southern Basin and the Slope. 2. pCO2 in the Bering Strait was dominated by the strong biological production in July and the coastal upwelling in September. 3. High DIC consumption via biological production made the Bering Shelf a strong CO2 sink during both voyages.Item Remote Sensing of Sea Surface pCO(2) in the Bering Sea in Summer Based on a Mechanistic Semi-Analytical Algorithm (MeSAA)(MDPI Ag, 6/30/16) Song,Xuelian; Bai,Yan; Cai,Wei-Jun; Chen,Chen-Tung Arthur; Pan,Delu; He,Xianqiang; Zhu,Qiankun; Xuelian Song , Yan Bai, Wei-Jun Cai, Chen-Tung Arthur Chen , Delu Pan, Xianqiang He and Qiankun Zhu; Cai, Wei-JunThe Bering Sea, one of the largest and most productive marginal seas, is a crucial carbon sink for the marine carbonate system. However, restricted by the tough observation conditions, few underway datasets of sea surface partial pressure of carbon dioxide (pCO(2)) have been obtained, with most of them in the eastern areas. Satellite remote sensing data can provide valuable information covered by a large area synchronously with high temporal resolution for assessments of pCO(2) that subsequently allow quantification of air-sea carbon dioxide 2 flux. However, pCO(2) in the Bering Sea is controlled by multiple factors and thus it is hard to Developmentelop a remote sensing algorithm with empirical regression methods. In this paper pCO(2) in the Bering Sea from July to September was derived based on a mechanistic semi-analytical algorithm (MeSAA). It was assumed that the observed pCO(2) can be analytically expressed as the sum of individual components controlled by major factors. First, a reference water mass that was minimally influenced by biology and mixing was identified in the central basin, and then thermodynamic and biological effects were parameterized for the entire area. Finally, we estimated pCO(2) with satellite temperature and chlorophyll data. Satellite results agreed well with the underway observations. Our study suggested that throughout the Bering Sea the biological effect on pCO(2) was more than twice as important as temperature, and contributions of other effects were relatively small. Furthermore, satellite observations demonstrate that the spring phytoplankton bloom had a delayed effect on summer pCO(2) but that the influence of this biological event varied regionally; it was more significant on the continental slope, with a later bloom, than that on the shelf with an early bloom. Overall, the MeSAA algorithm was not only able to estimate pCO(2) in the Bering Sea for the first time, but also provided a quantitative analysis of the contribution of various processes that influence pCO(2).Item Sea-ice loss accelerates carbon cycling and enhances seasonal extremes of acidification in the Arctic Chukchi Sea(Limnology and Oceanography Letters, 2024-02-05) Zhang, Yixing; Wu, Yingxu; Cai, Wei-Jun; Yi, Xiangqi; Gao, Xiang; Bi, Haibo; Zhuang, Yanpei; Chen, Liqi; Qi, DiThe Chukchi Sea shelf (CSS) is a highly productive region in the Arctic Ocean and it is highly efficient for absorbing atmospheric carbon dioxide and exporting and retaining carbon in the deep sea. However, with global warming, the carbon retention time in CSS may decrease, leading to less efficient carbon export. Here, we investigate the seasonal variability of carbonate chemistry in CSS using three sets of late- vs. early-summer reoccupations of the same transect. Our findings demonstrate substantially increased and rapid degradation of biologically produced organic matter and therefore acidification over time in the southern CSS due to earlier sea-ice retreat, resulting in significantly shorter carbon retention time. In sharp contrast, no increased degradation has been observed in the northern CSS where photosynthesis has just commenced. In the future, climate change would further diminish the carbon export capacity and exacerbate seasonal acidification not only within CSS but also across other polar coastal oceans. Scientific Significance Statement The Arctic Chukchi Sea shelf (CSS) is a prominent site for the biological drawdown of atmospheric carbon dioxide, which can subsequently be transported to the deep sea in the Arctic Ocean. The efficiency of carbon export is influenced by seasonal sea-ice formation and retreat: longer period of sea-ice opening results in shorter carbon retention time and reduced carbon export due to rapid recycling of organic matter. However, this process is poorly understood due to lack of observations. Here, we present three sets of late- vs. early-summer reoccupations along the same transect in the CSS. We unveil distinct spatial patterns of carbonate chemistry and subsurface acidification between the southern CSS and northern CSS. In the sCSS, degradation of biologically produced organic matter has occurred rapidly and caused subsurface acidification since early summer due to earlier sea-ice retreat; however, no such phenomenon is observed in the northern region. As Arctic warming continues in the future, these conditions are expected to persist, further diminishing carbon export capacity and exacerbating seasonal acidification.Item Using present-day observations to detect when anthropogenic change forces surface ocean carbonate chemistry outside preindustrial bounds(Copernicus Gesellschaft Mbh, 9/13/16) Sutton,Adrienne J.; Sabine,Christopher L.; Feely,Richard A.; Cai,Wei-Jun; Cronin,Meghan F.; McPhaden,Michael J.; Morell,Julio M.; Newton,Jan A.; Noh,Jae-Hoon; Olafsdottir,Solveig R.; Salisbury,Joseph E.; Send,Uwe; Vandemark,Douglas C.; Weller,Robert A.; Adrienne J. Sutton, Christopher L. Sabine, Richard A. Feely, Wei-Jun Cai, Meghan F. Cronin, Michael J. McPhaden, Julio M. Morell, Jan A. Newton, Jae-Hoon Noh, Solveig R. Olafsdottir, Joseph E. Salisbury, Uwe Send, Douglas C. Vandemark, and Robert A. Weller; Cai, Wei-JunOne of the major challenges to assessing the impact of ocean acidification on marine life is detecting and interpreting long-term change in the context of natural variability. This study addresses this need through a global synthesis of monthly pH and aragonite saturation state (Omega(arag)) climatologies for 12 open ocean, coastal, and coral reef locations using 3-hourly moored observations of surface seawater partial pressure of CO2 and pH collected together since as early as 2010. Mooring observations suggest open ocean subtropical and subarctic sites experience present-day surface pH and Omega(arag) conditions outside the bounds of preindustrial variability throughout most, if not all, of the year. In general, coastal mooring sites experience more natural variability and thus, more overlap with preindustrial conditions; however, present-day Omega(arag) conditions surpass biologically relevant thresholds associated with ocean acidification impacts on Mytilus californianus (Omega(arag) < 1.8) and Crassostrea gigas (Omega(arag) < 2.0) larvae in the California Current Ecosystem (CCE) and Mya arenaria larvae in the Gulf of Maine (Omega(arag) < 1.6). At the most variable mooring locations in coastal systems of the CCE, subseasonal conditions approached Omega(arag) = 1. Global and regional models and data syntheses of ship-based observations tended to underestimate seasonal variability compared to mooring observations. Efforts such as this to characterize all patterns of pH and Omega(arag) variability and change at key locations are fundamental to assessing present-day biological impacts of ocean acidification, further improving experimental design to interrogate organism response under real-world conditions, and improving predictive models and vulnerability assessments seeking to quantify the broader impacts of ocean acidification.Item Wastewater alkalinity addition as a novel approach for ocean negative carbon emissions(The Innovation, 2022-06-23) Cai, Wei-Jun; Jiao, NianzhiAnthropogenic CO2 emissions have greatly increased atmospheric CO2 contributing to global warming and leading to ocean acidification (Figure 1). As reflected in the recent IPCC report, the scientific community's consensus is that emissions reductions alone are not sufficient or timely enough to avoid a global warming catastrophe. Thus, negative-carbon-emission technologies are needed to avoid atmospheric CO2 overshoot scenarios and limit global warming to less than 2°C by the end of this century per the Paris Agreement. Due to the urgency and scale of the issue, multiple negative-emission technologies should be evaluated and adopted with broad community involvement to address our society's pressing climate crisis. The goal is to remove at least 10 Gt-CO2/year from the atmosphere by the mid to-late century,2 which is more than the current annual anthropogenic CO2 uptake by the global ocean (Figure 1). Among various ocean negative-carbon-emission approaches or ocean-based carbon dioxide removal (CDR) technologies, ocean alkalinity enhancement (OAE) is an approach that will decrease sea surface pCO2 via the addition of alkaline materials and promote CO2 uptake from the atmosphere. Additionally, as the oceanic dissolved inorganic carbon (DIC) reservoir is nearly 50 times the atmospheric CO2 content, the sequestered CO2 can remain in the ocean DIC pool as bicarbonate (HCO3−) for centuries. OAE is viewed with high confidence under the efficacy criterion and medium on environmental risk in the recent report by the National Academies of Sciences, Engineering, and Medicine.1