Aragonite saturation state (Ωarag) in surface and subsurface waters of the global oceans was calculated from up‐to‐date (through the year of 2012) ocean station dissolved inorganic carbon (DIC) and ...total alkalinity (TA) data. Surface Ωarag in the open ocean was always supersaturated (Ω > 1), ranging between 1.1 and 4.2. It was above 2.0 (2.0–4.2) between 40°N and 40°S but decreased toward higher latitude to below 1.5 in polar areas. The influences of water temperature on the TA/DIC ratio, combined with the temperature effects on inorganic carbon equilibrium and apparent solubility product (K′sp), explain the latitudinal differences in surface Ωarag. Vertically, Ωarag was highest in the surface mixed layer. Higher hydrostatic pressure, lower water temperature, and more CO2 buildup from biological activity in the absence of air‐sea gas exchange helped maintain lower Ωarag in the deep ocean. Below the thermocline, aerobic decomposition of organic matter along the pathway of global thermohaline circulation played an important role in controlling Ωarag distributions. Seasonally, surface Ωarag above 30° latitudes was about 0.06 to 0.55 higher during warmer months than during colder months in the open‐ocean waters of both hemispheres. Decadal changes of Ωarag in the Atlantic and Pacific Oceans showed that Ωarag in waters shallower than 100 m depth decreased by 0.10 ± 0.09 (−0.40 ± 0.37% yr−1) on average from the decade spanning 1989–1998 to the decade spanning 1998–2010.
Key Points
Climatological aragonite saturation in surface and subsurface global oceans are presented
Mechanisms controlling aragonite saturation state distributions are discussed
Subannual and decadal changes of aragonite saturation state are presented
Oceanic uptake of anthropogenic carbon dioxide (CO
2
) from the atmosphere has changed ocean biogeochemistry and threatened the health of organisms through a process known as ocean acidification ...(OA). Such large-scale changes affect ecosystem functions and can have impacts on societal uses, fisheries resources, and economies. In many large estuaries, anthropogenic CO
2
-induced acidification is enhanced by strong stratification, long water residence times, eutrophication, and a weak acid-base buffer capacity. In this article, we review how a variety of processes influence aquatic acid-base properties in estuarine waters, including coastal upwelling, river-ocean mixing, air-water gas exchange, biological production and subsequent aerobic and anaerobic respiration, calcium carbonate (CaCO
3
) dissolution, and benthic inputs. We emphasize the spatial and temporal dynamics of partial pressure of CO
2
(
p
CO
2
), pH, and calcium carbonate mineral saturation states. Examples from three large estuaries-Chesapeake Bay, the Salish Sea, and Prince William Sound-are used to illustrate how natural and anthropogenic processes and climate change may manifest differently across estuaries, as well as the biological implications of OA on coastal calcifiers.
The continental shelf region off the west coast of North America is seasonally exposed to water with a low aragonite saturation state by coastal upwelling of CO2-rich waters. To date, the spatial and ...temporal distribution of anthropogenic CO2 (Canth) within the CO2-rich waters is largely unknown. Here we adapt the multiple linear regression approach to utilize the GO-SHIP Repeat Hydrography data from the northeast Pacific to establish an annually updated relationship between Canth and potential density. This relationship was then used with the NOAA Ocean Acidification Program West Coast Ocean Acidification (WCOA) cruise data sets from 2007, 2011, 2012, and 2013 to determine the spatial variations of Canth in the upwelled water. Our results show large spatial differences in Canth in surface waters along the coast, with the lowest values (37–55 μmol kg−1) in strong upwelling regions off southern Oregon and northern California and higher values (51–63 μmol kg−1) to the north and south of this region. Coastal dissolved inorganic carbon concentrations are also elevated due to a natural remineralized component (Cbio), which represents carbon accumulated through net respiration in the seawater that has not yet degassed to the atmosphere. Average surface Canth is almost twice the surface remineralized component. In contrast, Canth is only about one third and one fifth of the remineralized component at 50 m and 100 m depth, respectively. Uptake of Canth has caused the aragonite saturation horizon to shoal by approximately 30–50 m since the preindustrial period so that undersaturated waters are well within the regions of the continental shelf that affect the shell dissolution of living pteropods. Our data show that the most severe biological impacts occur in the nearshore waters, where corrosive waters are closest to the surface. Since the pre-industrial times, pteropod shell dissolution has, on average, increased approximately 19–26% in both nearshore and offshore waters.
Display omitted
•The coastal waters off the US west coast are seasonally exposed to waters with low aragonite saturation.•Large spatial differences in Canth occur in surface waters along the coast.•Average surface Canth is almost twice the surface remineralized component (Cbio).•Uptake of Canth has caused the aragonite saturation horizon to shoal by approximately 30–50 m.•Pteropod shell dissolution has increased approximately 19–26% since the pre-industrial era.
Based on measurements from the WOCE/JGOFS global CO2 survey, the CLIVAR/CO2 Repeat Hydrography Program and the Canadian Line P survey, we have observed an average decrease of 0.34% yr−1 in the ...saturation state of surface seawater in the Pacific Ocean with respect to aragonite and calcite. The upward migrations of the aragonite and calcite saturation horizons, averaging about 1 to 2 m yr−1, are the direct result of the uptake of anthropogenic CO2 by the oceans and regional changes in circulation and biogeochemical processes. The shoaling of the saturation horizon is regionally variable, with more rapid shoaling in the South Pacific where there is a larger uptake of anthropogenic CO2. In some locations, particularly in the North Pacific Subtropical Gyre and in the California Current, the decadal changes in circulation can be the dominant factor in controlling the migration of the saturation horizon. If CO2 emissions continue as projected over the rest of this century, the resulting changes in the marine carbonate system would mean that many coral reef systems in the Pacific would no longer be able to sustain a sufficiently high rate of calcification to maintain the viability of these ecosystems as a whole, and these changes perhaps could seriously impact the thousands of marine species that depend on them for survival.
Key Points
The saturation state of surface waters decreased by an average of 0.34% per year
The aragonite and calcite saturation horizons shoal an average of 1‐2 m per yr
The shoaling of the saturation horizon is regionally variable
The contribution of carbonate-producing benthic organisms to the global marine carbon budget has been overlooked, the prevailing view being that calcium carbonate (CaCO
3
) is predominantly produced ...and exported by marine plankton in the "biological pump." Here, we provide the first estimation of the global contribution of echinoderms to the marine inorganic and organic carbon cycle, based on organism-level measurements from species of the five echinoderm classes. Echinoderms' global CaCO
3
contribution amounts to ~0.861 Pg CaCO
3
/yr (0.102 Pg C/yr of inorganic carbon) as a production rate, and ~2.11 Pg CaCO
3
(0.25 Pg C of inorganic carbon) as a standing stock from the shelves, slopes, and abyssal depths. Echinoderm inorganic carbon production (0.102 Pg C/yr) is less than the global pelagic production (0.4-1.8 Pg C/yr) and similar to the estimates for carbonate shelves globally (0.024-0.120 Pg C/yr). Echinoderm CaCO
3
production per unit area is ~27.01 g CaCO
3
·m
−2
·yr
−1
(3.24 g C·m
−2
·yr
−1
as inorganic carbon) on a global scale for all areas, with a standing stock of ~63.34 g CaCO
3
/m
2
(7.60 g C/m
2
as inorganic carbon), and ~7.97 g C/m
2
as organic carbon. The shelf production alone is 77.91 g CaCO
3
·m
−2
·yr
−1
(9.35 g C·m
−2
·yr
−1
as inorganic carbon) in contrast to 2.05 g CaCO
3
·m
−2
·yr
−1
(0.24 g C·m
−2
·yr
−1
as inorganic carbon) for the slope on a global scale. The biogeography of the CaCO
3
standing stocks of echinoderms showed strong latitudinal variability. More than 80% of the global CaCO
3
production from echinoderms occurs between 0 and 800 m, with the highest contribution attributed to the shelf and upper slope. We provide a global distribution of echinoderm populations in the context of global calcite saturation horizons, since undersaturated waters with respect to mineral phases are surfacing. This shallowing is a direct consequence of ocean acidification, and in some places it may reach the shelf and upper slope permanently, where the highest CaCO
3
standing stocks from echinoderms originate. These organism-level data contribute substantially to the assessment of global carbonate inventories, which at present are poorly estimated. Additionally, it is desirable to include these benthic compartments in coupled global biogeochemical models representing the "biological pump" and its feedbacks, since at present all efforts have focused on pelagic processes, dominated by coccolithophores. The omission of the benthic processes from modeling will only diminish the understanding of elemental fluxes at large scales and any future prediction of climate change scenarios.
A successful integrated ocean acidification (OA) observing network must include 1) scientists and technicians from a range of disciplines (from physics to chemistry to biology to technology ...development) and across the globe; 2) government, private, and intergovernmental support; 3) regional cohorts working together on regionally specific issues; 4) publicly accessible data from the open ocean to coastal to estuarine systems; 5) close integration with other networks focusing on related measurements or issues including the social and economic consequences of OA; and 6) observation-based informational products useful for decision making such as management of fisheries and aquaculture. The Global Ocean Acidification Observing Network (GOA-ON), a key player in this vision, seeks to expand and enhance geographic extent and availability of coastal and open ocean observing data to ultimately inform adaptive measures and policy action, especially in support of the United Nations 2030 Agenda for Sustainable Development. GOA-ON works to empower and support regional collaborative networks such as the Latin American Ocean Acidification Network, supports new scientists entering the field with training, mentorship, and equipment, refines approaches for tracking biological impacts, and stimulates development of lower-cost methodology and technologies allowing for wider participation of scientists. GOA-ON seeks to collaborate with and complement work done by other observing networks such as those focused on carbon flux into the ocean, tracking of carbon and oxygen in the ocean, observing biological diversity, and determining short- and long-term variability in these and other ocean parameters through space and time.
Decadal changes in Pacific carbon Sabine, Christopher L.; Feely, Richard A.; Millero, Frank J. ...
Journal of Geophysical Research - Oceans,
July 2008, Letnik:
113, Številka:
C7
Journal Article
Recenzirano
Odprti dostop
This paper uses the extended multiple linear regression (eMLR) technique to investigate changes over the last decade in dissolved inorganic carbon (DIC) inventories on a meridional line (P16 along ...152°W) up the central Pacific and on a zonal line (P02 along 30°N) across the North Pacific. Maximum changes in the total DIC concentrations along P02 are 15–20 μmol kg−1 over 10 years, somewhat higher than the ∼1 μmol kg−1 a−1 increase in DIC expected based on the rate of atmospheric CO2 increase. The maximum changes of 15–20 μmol kg−1 along the P16 line over the 14/15‐year time frame fit with the expected magnitude of the anthropogenic signal, but there is a deeper than expected penetration of the signal in the North Pacific compared to the South Pacific. The effect of varying circulation on the total DIC change, based on decadal alterations of the apparent oxygen utilization rate, is estimated to be greater than 10 μmol kg−1 in the North Pacific, accounting for as much as 80% of the total DIC change in that region. The average anthropogenic CO2 inventory increase along 30°N between 1994 and 2004 was 0.43 mol m−2 a−1, with much higher inventories in the western Pacific. Along P16, the average Northern Hemisphere increase was 0.25 mol m−2 a−1 between 1991/1992 and 2006 compared to an average Southern Hemisphere anthropogenic CO2 inventory increase between 1991 and 2005 of 0.41 mol m−2 a−1.
This study uses nearly 25,000 carbon measurements from the WOCE/JGOFS global CO2 survey to examine the distribution of dissolved inorganic carbon (DIC) and total alkalinity (TA) in the Indian Ocean. ...Shallow and intermediate distributions of inorganic carbon do not strictly follow temperature and salinity because of differing surface gradients and vertical biological processes that work to modify the circulation derived features. Anthropogenic CO2 has increased the shallow DIC by as much as 3%, decreasing the vertical DIC gradient. Deep ocean DIC and TA increase toward the north because of the decomposition and dissolution of organic and inorganic particles. Calcite saturation depths range from 2900–3900 m with the deepest saturation depth in the central Indian Ocean. Variations of aragonite saturation depth (200–1400 m) are similar to calcite, but the deepest saturations are in the southwestern Indian Ocean. The shallowest aragonite saturation depths are found in the Bay of Bengal. In the northern Arabian Sea and Bay of Bengal, the current aragonite saturations are 100 and 200 m shallower, respectively, than in preindustrial times. Estimates of carbonate dissolution rates on isopycnal surfaces range from 0.017 to 0.083 μmol kg−1 yr−1 in deep waters. Upper water column dissolution rates range from 0 to 0.73 μmol kg−1 yr−1, with a local maximum occurring in intermediate waters just below the aragonite saturation horizon. Dissolution is also generally higher north of the Chemical Front at 10–20°S. There is some evidence for significant sedimentary sources in the northern Indian Ocean.
As a part of the JGOFS synthesis and modeling project, researchers have been working to synthesize the WOCE/JGOFS/DOE/NOAA global CO sub(2) survey data to better understand carbon cycling processes ...in the oceans. Working with international investigators we have compiled a Pacific Ocean data set with over 35,000 unique samples analyzed for at least two carbon species, oxygen, nutrients, chlorofluorocarbon (CFC) tracers, and hydrographic parameters. We use these data here to estimate in-situ oxygen utilization rates (OUR) and organic carbon remineralization rates within the upper water column of the Pacific Ocean. OURs are derived from the observed apparent oxygen utilization (AOU) and the water age estimates based on CFCs in the upper water and natural radiocarbon in deep waters. The rates are generally highest just below the euphotic zone and decrease with depth to values that are much lower and nearly constant in water deeper than 1200 m. OURs ranged from about 0.02-10 mu mol kg super(-1)yr super(-1) in the upper water masses from about 100-1000 m, and averaged = 0.10 mu mol kg super(-1)yr super(-1) in deep waters below 1200 m. The OUR data can be used to directly estimate organic carbon remineralization rates using the C:O Redfield ratio given in Anderson and Sarmiento (1994). When these rates are integrated we obtain an estimate of 5.3 plus or minus 1 Pg C yr super(-1) for the remineralization of organic carbon in the upper water column of the Pacific Ocean.
Ocean acidification (OA) along the US West Coast is intensifying faster than observed in the global ocean. This is particularly true in nearshore regions (<200 m) that experience a lower buffering ...capacity while at the same time providing important habitats for ecologically and economically significant species. While the literature on the effects of OA from laboratory experiments is voluminous, there is little understanding of present-day OA in-situ effects on marine life. Dungeness crab (Metacarcinus magister) is perennially one of the most valuable commercial and recreational fisheries. We focused on establishing OA-related vulnerability of larval crustacean based on mineralogical and elemental carapace to external and internal carapace dissolution by using a combination of different methods ranging from scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping and X-ray diffraction. By integrating carapace features with the chemical observations and biogeochemical model hindcast, we identify the occurrence of external carapace dissolution related to the steepest Ω calcite gradients (∆Ωcal,60) in the water column. Dissolution features are observed across the carapace, pereopods (legs), and around the calcified areas surrounding neuritic canals of mechanoreceptors. The carapace dissolution is the most extensive in the coastal habitats under prolonged (1-month) long exposure, as demonstrated by the use of the model hindcast. Such dissolution has a potential to destabilize mechanoreceptors with important sensory and behavioral functions, a pathway of sensitivity to OA. Carapace dissolution is negatively related to crab larval width, demonstrating a basis for energetic trade-offs. Using a retrospective prediction from a regression models, we estimate an 8.3% increase in external carapace dissolution over the last two decades and identified a set of affected OA-related sublethal pathways to inform future risk assessment studies of Dungeness crabs.
Display omitted
•Coastal habitats with the steepest ocean acidification gradients are most detrimental for larval Dungeness crabs.•Severe carapace dissolution was observed in larval Dungeness crabs along the US west coast.•Mechanoreceptors with important sensory and behavioral functions were destabilized.•Dissolution is negatively related to the growth, demonstrating energetic trade-offs.•10% dissolution increase over the last two decades estimated due to atmospheric CO2.
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