Sabine Christopher L.

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Sabine

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Christopher L.

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Comment on “Modern-age buildup of CO2 and its effects on seawater acidity and salinity” by Hugo A. Loáiciga

(American Geophysical Union, 2007-09-25) Caldeira, Ken ; Archer, David ; Barry, James P. ; Bellerby, Richard G. J. ; Brewer, Peter G. ; Cao, Long ; Dickson, Andrew G. ; Doney, Scott C. ; Elderfield, Henry ; Fabry, Victoria J. ; Feely, Richard A. ; Gattuso, Jean-Pierre ; Haugan, Peter M. ; Hoegh-Guldberg, Ove ; Jain, Atul K. ; Kleypas, Joan A. ; Langdon, Chris ; Orr, James C. ; Ridgwell, Andy ; Sabine, Christopher L. ; Seibel, Brad A. ; Shirayama, Yoshihisa ; Turley, Carol ; Watson, Andrew J. ; Zeebe, Richard E.
Comparison of CO2 dynamics and air-sea exchange in differing tropical reef environments

( 2013-01-17) Drupp, Patrick S. ; De Carlo, Eric H. ; Mackenzie, Fred T. ; Sabine, Christopher L. ; Feely, Richard A. ; Shamberger, Kathryn E. F.

An array of MAPCO2 buoys, CRIMP-2, Ala Wai, and Kilo Nalu, deployed in the coastal waters of Hawaii have produced multiyear high temporal resolution CO2 records in three different coral reef environments off the island of Oahu, Hawaii. This study, which includes data from June 2008-December 2011, is part of an integrated effort to understand the factors that influence the dynamics of CO2-carbonic acid system parameters in waters surrounding Pacific high island coral reef ecosystems and subject to differing natural and anthropogenic stresses. The MAPCO2 buoys are located on the Kaneohe Bay backreef, and fringing reef sites on the south shore of O’ahu, Hawai’i. The buoys measure CO2 and O2 in seawater and in the atmosphere at 3-hour intervals, as well as other physical and biogeochemical parameters (CTD, chlorophyll-a, turbidity). The buoy records, combined with data from synoptic spatial sampling, have allowed us to examine the interplay between biological cycles of productivity/respiration and calcification/dissolution and biogeochemical and physical forcings on hourly to inter-annual time scales. Air-sea CO2 gas exchange was also calculated to determine if the locations were sources or sinks of CO2 over seasonal, annual, and interannual time periods. Net annualized fluxes for CRIMP-2, Ala Wai, and Kilo Nalu over the entire study period were 1.15 mol C m-2 yr-1, 0.045 mol C m-2 yr-1, and -0.0056 mol C m-2 yr-1, respectively, where positive values indicate a source or a CO2 flux from the water to the atmosphere, and negative values indicate a sink or flux of CO2 from the atmosphere into the water. These values are of similar magnitude to previous estimates in Kaneohe Bay as well as those reported from other tropical reef environments. Total alkalinity (AT) was measured in conjunction with pCO2 and the carbonic acid system was calculated to compare with other reef systems and open ocean values around Hawaii. These findings emphasize the need for high-resolution data of multiple parameters when attempting to characterize the carbonic-acid system in locations of highly variable physical, chemical, and biological parameters (e.g. coastal systems, reefs).
WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-4 2007 mooring turnaround cruise report

(Woods Hole Oceanographic Institution, 2008-01) Whelan, Sean P. ; Plueddemann, Albert J. ; Lukas, Roger ; Lord, Jeffrey ; Lethaby, Paul ; Snyder, Jefrey ; Smith, Jason C. ; Bahr, Frank B. ; Galbraith, Nancy R. ; Sabine, Christopher L.

The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the HOT program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds. These observations will be used to investigate air–sea interaction processes related to climate variability. The first three WHOTS moorings (WHOTS-1 through 3) were deployed in August 2004, July 2005 and June 2006, respectively. This report documents recovery of the WHOTS-3 mooring and deployment of the fourth mooring (WHOTS-4). Both moorings used Surlyn foam buoys as the surface element and were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 155 m of the moorings were outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of the University of Hawaii. A pCO2 system was installed on the WHOT-3 buoy in a cooperative effort with Chris Sabine at the Pacific Marine Environmental Laboratory. The WHOTS mooring turnaround was done on the University of Hawaii research vessel Kilo Moana, Cruise KM-07-08, by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution. The cruise took place between 24 June and 1 July 2007. Operations began with deployment of the WHOTS-4 mooring on 25 June at approximately 22°40.2′N, 157°57.0′W in 4756 m of water. This was followed by meteorological intercomparisons and CTDs at the WHOTS-4 and WHOTS-3 sites. The WHOTS-3 mooring was recovered on June 28th followed by CTD operations at the HOT site and shipboard meteorological observations at several sites to the south of the mooring site. This report describes these cruise operations, as well as some of the in-port operations and pre-cruise buoy preparations.
Hawaii coastal seawater CO2 network: A statistical evaluation of a decade of observations on tropical coral reefs.

(Frontiers Media, 2019-05-07) Terlouw, Gerianne J. ; Knor, Lucie A. C. M. ; De Carlo, Eric H. ; Drupp, Patrick S. ; Mackenzie, Fred T. ; Li, Yuan Hui ; Sutton, Adrienne J. ; Plueddemann, Albert J. ; Sabine, Christopher L.

A statistical evaluation of nearly 10 years of high-resolution surface seawater carbon dioxide partial pressure (pCO2) time-series data collected from coastal moorings around O’ahu, Hawai’i suggest that these coral reef ecosystems were largely a net source of CO2 to the atmosphere between 2008 and 2016. The largest air-sea flux (1.24 ± 0.33 mol m−2 yr−1) and the largest variability in seawater pCO2 (950 μatm overall range or 8x the open ocean range) were observed at the CRIMP-2 site, near a shallow barrier coral reef system in Kaneohe Bay O’ahu. Two south shore sites, Kilo Nalu and Ala Wai, also exhibited about twice the surface water pCO2 variability of the open ocean, but had net fluxes that were much closer to the open ocean than the strongly calcifying system at CRIMP-2. All mooring sites showed the opposite seasonal cycle from the atmosphere, with the highest values in the summer and lower values in the winter. Average coastal diurnal variabilities ranged from a high of 192 μatm/day to a low of 32 μatm/day at the CRIMP-2 and Kilo Nalu sites, respectively, which is one to two orders of magnitude greater than observed at the open ocean site. Here we examine the modes and drivers of variability at the different coastal sites. Although daily to seasonal variations in pCO2 and air-sea CO2 fluxes are strongly affected by localized processes, basin-scale climate oscillations also affect the variability on interannual time scales.
WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-5 2008 mooring turnaround cruise report

(Woods Hole Oceanographic Institution, 2009-04) Whelan, Sean P. ; Lord, Jeffrey ; Weller, Robert A. ; Lukas, Roger ; Santiago-Mandujano, Fernando ; Snyder, Jefrey ; Lethaby, Paul ; Bahr, Frank B. ; Sabine, Christopher L. ; Smith, Jason C. ; Bouchard, Paul R. ; Galbraith, Nancy R.

The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the HOT program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds. These observations will be used to investigate air–sea interaction processes related to climate variability. The first four WHOTS moorings (WHOTS-1 through 4) were deployed in August 2004, July 2005, June 2006, and June 2007, respectively. This report documents recovery of the WHOTS-4 mooring and deployment of the fifth mooring (WHOTS-5). Both moorings used Surlyn foam buoys as the surface element and were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 155 m of the moorings were outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of the University of Hawaii. A pCO2 system was installed on the WHOTS-5 buoy in a cooperative effort with Chris Sabine at the Pacific Marine Environmental Laboratory. The WHOTS mooring turnaround was done on the University of Hawaii research vessel Kilo Moana, Cruise KM-08-08, by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution. The cruise took place between 3 and 11 June 2008. Operations began with deployment of the WHOTS-5 mooring on 5 June at approximately 22°46.1'N, 157°54.1'W in 4702 m of water. This was followed by meteorological intercomparisons and CTDs at the WHOTS-4 site. A period of calmer weather was taken advantage of to recover WHOTS-4 on 6 June 2008. The Kilo Moana then returned to the WHOTS-5 mooring for CTD operations and meteorological intercomparisons. This report describes these cruise operations, as well as some of the in-port operations and pre-cruise buoy preparations.
WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-6 2009 mooring turnaround cruise report

(Woods Hole Oceanographic Institution, 2010-02) Whelan, Sean P. ; Santiago-Mandujano, Fernando ; Bradley, Frank ; Plueddemann, Albert J. ; Barista, Ludovic ; Ryder, James R. ; Lukas, Roger ; Lethaby, Paul ; Snyder, Jefrey ; Sabine, Christopher L. ; Stanitski, Diane ; Rapp, Anita D. ; Fairall, Christopher W. ; Pezoa, Sergio ; Galbraith, Nancy R. ; Lord, Jeffrey ; Bahr, Frank B.

The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the Hawaiian Ocean Timeseries (HOT) program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds. These observations will be used to investigate air–sea interaction processes related to climate variability. The first WHOTS mooring (WHOTS-1) was deployed in August 2004. Turnaround cruises for successive moorings (WHOTS-2 through WHOTS-5) have typically been in either June or July. This report documents recovery of the WHOTS-5 mooring and deployment of the sixth mooring (WHOTS-6). The moorings utilize Surlyn foam buoys as the surface element and are outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 155 m of the mooring is outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of the University of Hawaii (UH). A pCO2 system is installed on the buoy in a cooperative effort with Chris Sabine at the Pacific Marine Environmental Laboratory. Dr. Frank Bradley, CSIRO, Australia, assisted with meteorological sensor comparisons. A NOAA “Teacher at Sea” and a NOAA “Teacher in the Lab” participated in the cruise. The WHOTS mooring turnaround was done on the University of Hawaii research vessel Kilo Moana, Cruise KM-09-16, by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution in cooperation with UH and NOAA’s Earth System Research Laboratory, Physical Sciences Division (ESRL/PSD). The cruise took place between 9 and 17 July 2009. Operations began with deployment of the WHOTS-6 mooring on 10 July at approximately 22°40.0'N, 157°57.0'W in 4758 m of water. This was followed by meteorological intercomparisons and CTDs at the WHOTS-6 and WHOTS-5 sites. The WHOTS-5 mooring was recovered on 15 July 2009. The Kilo Moana then moved to the HOT central site (22°45.0'N, 158°00.0'W) for CTD casts. This report describes the cruise operations in more detail, as well as some of the in-port operations and pre-cruise buoy preparations.
Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms

( 2005-07-29) Orr, James C. ; Fabry, Victoria J. ; Aumont, Olivier ; Bopp, Laurent ; Doney, Scott C. ; Feely, Richard A. ; Gnanadesikan, Anand ; Gruber, Nicolas ; Ishida, Akio ; Joos, Fortunat ; Key, Robert M. ; Lindsay, Keith ; Maier-Reimer, Ernst ; Matear, Richard J. ; Monfray, Patrick ; Mouchet, Anne ; Najjar, Raymond G. ; Plattner, Gian-Kasper ; Rodgers, Keith B. ; Sabine, Christopher L. ; Sarmiento, Jorge L. ; Schlitzer, Reiner ; Slater, Richard D. ; Totterdell, Ian J. ; Weirig, Marie-France ; Yamanaka, Yasuhiro ; Yool, Andrew

The surface ocean is everywhere saturated with respect to calcium carbonate (CaCO3). Yet increasing atmospheric CO2 reduces ocean pH and carbonate ion concentrations [CO32−] and thus the level of saturation. Reduced saturation states are expected to affect marine calcifiers even though it has been estimated that all surface waters will remain saturated for centuries. Here we show, however, that some surface waters will become undersaturated within decades. When atmospheric CO2 reaches 550 ppmv, in year 2050 under the IS92a business-as-usual scenario, Southern Ocean surface waters begin to become undersaturated with respect to aragonite, a metastable form of CaCO3. By 2100 as atmospheric CO2 reaches 788 ppmv, undersaturation extends throughout the entire Southern Ocean (< 60°S) and into the subarctic Pacific. These changes will threaten high-latitude aragonite secreting organisms including cold-water corals, which provide essential fish habitat, and shelled pteropods, an abundant food source for marine predators.
WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-8 2011 mooring turnaround cruise report

(Woods Hole Oceanographic Institution, 2012-04) Whelan, Sean P. ; Lord, Jeffrey ; Duncombe Rae, Chris M. ; Plueddemann, Albert J. ; Snyder, Jefrey ; Nosse, Craig ; Lukas, Roger ; Boylan, Patrick ; Pietro, Benjamin ; Bariteau, Ludovic ; Sabine, Christopher L. ; Pezoa, Sergio

The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the HOT program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds. These observations will be used to investigate air–sea interaction processes related to climate variability. This report documents recovery of the seventh WHOTS mooring (WHOTS-7) and deployment of the eighth mooring (WHOTS-8). Both moorings used Surlyn foam buoys as the surface element and were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 155 m of the moorings were outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of the University of Hawaii. A pCO2 system was installed on the WHOTS-8 buoy in a cooperative effort with Chris Sabine at the Pacific Marine Environmental Laboratory. A set of radiometers were installed in cooperation with Sam Laney at WHOI. The WHOTS mooring turnaround was done on the NOAA ship Hi’ialakai by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution. The cruise took place between 5 July and 13 July 2011. Operations began with deployment of the WHOTS-8 mooring on 6 July. This was followed by meteorological intercomparisons and CTDs. Recovery of WHOTS-7 took place on 11 July 2011. This report describes these cruise operations, as well as some of the in-port operations and pre-cruise buoy preparations.
International Carbon Coordination : Roger Revelle’s legacy in the Intergovernmental Oceanographic Commission

(Oceanography Society, 2010-09) Sabine, Christopher L. ; Ducklow, Hugh W. ; Hood, Maria

Since its inception in 1960, the Intergovernmental Oceanographic Commission (IOC) has been responsible for organizing and coordinating the scientific investigation of ocean carbon. Roger Revelle (Scripps Institution of Oceanography) first articulated the principal need for international and intergovernmental coordination to address global-scale problems such as climate change when IOC was first developed. Regional to global-scale carbon studies started in earnest with the International Decade of Ocean Exploration (IDOE) and Geochemical Ocean Sections Study (GEOSECS) programs in the 1970s, but they were hampered by technological barriers that limited both the precision of carbon system measurements and the greater sampling frequency needed for a comprehensive global view. In 1979, IOC established the Committee on Climate Change and the Ocean (CCCO) with Revelle as Chair. CCCO called for a carbon observation program and sampling strategy that could determine the global oceanic CO2 inventory to an accuracy of 10–20 petagrams of carbon (Pg C). Perfection of the coulometric analysis technique of total dissolved inorganic carbon (DIC) in seawater by Ken Johnson (University of Rhode Island) and introduction of certified reference materials for DIC and alkalinity by Andrew Dickson (Scripps Institution of Oceanography) made such a study possible. The first global survey of ocean CO2 was carried out under the joint sponsorship of IOC and the Scientific Committee on Oceanic Research (SCOR) in the Joint Global Ocean Flux Study (JGOFS) and the World Ocean Circulation Experiment (WOCE) in the 1990s. With these programs and underway pCO2 measuring systems on research vessels and ships of opportunity, ocean carbon data grew exponentially, reaching about a million total measurements by 2002 when Taro Takahashi (Lamont-Doherty Earth Observatory) and others provided the first robust mapping of surface ocean CO2. Using a new approach developed by Nicolas Gruber (ETH Zürich) and colleagues with JGOFS-WOCE and other synthesized data sets, one of this article’s authors (Sabine) with a host of coauthors estimated that the total accumulation of anthropogenic CO2 between 1800 and 1994 was 118 ± 19 Pg C, just within the uncertainty goals set by JGOFS and IOC prior to the global survey. Today, ocean carbon activities are coordinated through the International Ocean Carbon Coordination Project (IOCCP). Ocean carbon measurements now accumulate at a rate of over a million measurements per year—matching the total number achieved over the first three decades of ocean carbon studies. IOCCP is actively working to combine these data into uniform data sets that the community can use to better understand ocean carbon uptake and storage. The problem of ocean acidification caused by uptake of anthropogenic CO2 is now a major target of IOC and IOCCP.
Variability and trends in surface seawater pCO2 and CO2 flux in the Pacific Ocean

(John Wiley & Sons, 2017-06-12) Sutton, Adrienne J. ; Wanninkhof, Rik ; Sabine, Christopher L. ; Feely, Richard A. ; Cronin, Meghan F. ; Weller, Robert A.

Variability and change in the ocean sink of anthropogenic carbon dioxide (CO2) have implications for future climate and ocean acidification. Measurements of surface seawater CO2 partial pressure (pCO2) and wind speed from moored platforms are used to calculate high-resolution CO2 flux time series. Here we use the moored CO2 fluxes to examine variability and its drivers over a range of time scales at four locations in the Pacific Ocean. There are significant surface seawater pCO2, salinity, and wind speed trends in the North Pacific subtropical gyre, especially during winter and spring, which reduce CO2 uptake over the 10 year record of this study. Starting in late 2013, elevated seawater pCO2 values driven by warm anomalies cause this region to be a net annual CO2 source for the first time in the observational record, demonstrating how climate forcing can influence the timing of an ocean region shift from CO2 sink to source.
Pacific anthropogenic carbon between 1991 and 2017

(American Geophysical Union, 2019-04-29) Carter, Brendan ; Feely, Richard A. ; Wanninkhof, Rik ; Kouketsu, Shinya ; Sonnerup, Rolf E. ; Pardo, Paula Conde ; Sabine, Christopher L. ; Johnson, Gregory C. ; Sloyan, Bernadette M. ; Murata, Akihiko ; Mecking, Sabine ; Tilbrook, Bronte ; Speer, Kevin G. ; Talley, Lynne D. ; Millero, Frank J. ; Wijffels, Susan E. ; Macdonald, Alison M. ; Gruber, Nicolas ; Bullister, John L.

We estimate anthropogenic carbon (Canth) accumulation rates in the Pacific Ocean between 1991 and 2017 from 14 hydrographic sections that have been occupied two to four times over the past few decades, with most sections having been recently measured as part of the Global Ocean Ship‐based Hydrographic Investigations Program. The rate of change of Canth is estimated using a new method that combines the extended multiple linear regression method with improvements to address the challenges of analyzing multiple occupations of sections spaced irregularly in time. The Canth accumulation rate over the top 1,500 m of the Pacific increased from 8.8 (±1.1, 1σ) Pg of carbon per decade between 1995 and 2005 to 11.7 (±1.1) PgC per decade between 2005 and 2015. For the entire Pacific, about half of this decadal increase in the accumulation rate is attributable to the increase in atmospheric CO2, while in the South Pacific subtropical gyre this fraction is closer to one fifth. This suggests a substantial enhancement of the accumulation of Canth in the South Pacific by circulation variability and implies that a meaningful portion of the reinvigoration of the global CO2 sink that occurred between ~2000 and ~2010 could be driven by enhanced ocean Canth uptake and advection into this gyre. Our assessment suggests that the accuracy of Canth accumulation rate reconstructions along survey lines is limited by the accuracy of the full suite of hydrographic data and that a continuation of repeated surveys is a critical component of future carbon cycle monitoring.
Quantifying net community production and calcification at Station ALOHA near Hawai‘i: Insights and limitations from a dual tracer carbon budget approach

(American Geophysical Union, 2023-07-02) Knor, Lucie A. C. M. ; Sabine, Christopher L. ; Sutton, Adrienne J. ; White, Angelicque E. ; Potemra, James T. ; Weller, Robert A.

A budget approach is used to disentangle drivers of the seasonal mixed layer carbon cycle at Station ALOHA (A Long-term Oligotrophic Habitat Assessment) in the North Pacific Subtropical Gyre (NPSG). The budget utilizes data from the WHOTS (Woods Hole—Hawaii Ocean Time-series Site) mooring, and the ship-based Hawai'i Ocean Time-series (HOT) in the NPSG, a region of significant oceanic carbon uptake. Parsing the carbon variations into process components allows an assessment of both the proportional contributions of mixed layer carbon drivers and the seasonal interplay of drawdown and supply from different processes. Annual net community production reported here is at the lower end of previously published data, while net community calcification estimates are 4- to 7-fold higher than available sediment trap data, the only other estimate of calcium carbonate export at this location. Although the observed seasonal cycle in dissolved inorganic carbon in the NPSG has a relatively small amplitude, larger fluxes offset each other over an average year. Major supply comes from physical transport, especially lateral eddy transport throughout the year and entrainment in the winter, offset by biological carbon uptake in the spring. Gas exchange plays a smaller role, supplying carbon to the surface ocean between Dec-May and outgassing in Jul-Oct. Evaporation-precipitation (E-P) is variable with precipitation prevailing in the first half and evaporation in the second half of the year. The observed total alkalinity signal is largely governed by E-P with a somewhat stronger net calcification signal in the wintertime.
Seasonal asymmetry in the evolution of surface ocean pCO2 and pH thermodynamic drivers and the influence on sea‐air CO2 flux

(John Wiley & Sons, 2018-10-11) Fassbender, Andrea ; Rodgers, Keith B. ; Palevsky, Hilary I. ; Sabine, Christopher L.

It has become clear that anthropogenic carbon invasion into the surface ocean drives changes in the seasonal cycles of carbon dioxide partial pressure (pCO2) and pH. However, it is not yet known whether the resulting sea‐air CO2 fluxes are symmetric in their seasonal expression. Here we consider a novel application of observational constraints and modeling inferences to test the hypothesis that changes in the ocean's Revelle factor facilitate a seasonally asymmetric response in pCO2 and the sea‐air CO2 flux. We use an analytical framework that builds on observed sea surface pCO2 variability for the modern era and incorporates transient dissolved inorganic carbon concentrations from an Earth system model. Our findings reveal asymmetric amplification of pCO2 and pH seasonal cycles by a factor of two (or more) above preindustrial levels under Representative Concentration Pathway 8.5. These changes are significantly larger than observed modes of interannual variability and are relevant to climate feedbacks associated with Revelle factor perturbations. Notably, this response occurs in the absence of changes to the seasonal cycle amplitudes of dissolved inorganic carbon, total alkalinity, salinity, and temperature, indicating that significant alteration of surface pCO2 can occur without modifying the physical or biological ocean state. This result challenges the historical paradigm that if the same amount of carbon and nutrients is entrained and subsequently exported, there is no impact on anthropogenic carbon uptake. Anticipation of seasonal asymmetries in the sea surface pCO2 and CO2 flux response to ocean carbon uptake over the 21st century may have important implications for carbon cycle feedbacks.
Nonuniform ocean acidification and attenuation of the ocean carbon sink

(John Wiley & Sons, 2017-08-16) Fassbender, Andrea ; Sabine, Christopher L. ; Palevsky, Hilary I.

Surface ocean carbon chemistry is changing rapidly. Partial pressures of carbon dioxide gas (pCO2) are rising, pH levels are declining, and the ocean's buffer capacity is eroding. Regional differences in short-term pH trends primarily have been attributed to physical and biological processes; however, heterogeneous seawater carbonate chemistry may also be playing an important role. Here we use Surface Ocean CO2 Atlas Version 4 data to develop 12 month gridded climatologies of carbonate system variables and explore the coherent spatial patterns of ocean acidification and attenuation in the ocean carbon sink caused by rising atmospheric pCO2. High-latitude regions exhibit the highest pH and buffer capacity sensitivities to pCO2 increases, while the equatorial Pacific is uniquely insensitive due to a newly defined aqueous CO2 concentration effect. Importantly, dissimilar regional pH trends do not necessarily equate to dissimilar acidity ([H+]) trends, indicating that [H+] is a more useful metric of acidification.

Sabine Christopher L.

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