scholarly journals Long-term variations in ocean acidification indices in the Northwest Pacific from 1993 to 2018

2021 ◽  
Vol 168 (3-4) ◽  
Author(s):  
Miho Ishizu ◽  
Yasumasa Miyazawa ◽  
Xinyu Guo
Keyword(s):  
Ocean Acidification ◽  
Observational Data ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sink ◽  
Kuroshio Extension ◽  
Biogeochemical Model ◽  
Northwest Pacific ◽  
Subarctic Region ◽  
Long Term Variations

AbstractLong-term variations in ocean acidification indices in the Northwest Pacific were examined using observational data and a biogeochemical model with an operational ocean model product for the period 1993–2018. The model and observational data for the surface ocean (< 100-m depth) exhibit consistent patterns of ocean acidification in the subtropical and Kuroshio Extension regions and relative alkalinization (i.e., reduced acidification) in the subarctic region of the Northwest Pacific. Below 100-m depth, acidification dominated in the subtropical regions and alkalinization in the subarctic regions. We attribute the excess acidification in the subtropical and Kuroshio regions to the vertical mixing of dissolved inorganic carbon (DIC) exceeding the DIC release by air–sea exchange. These regional differences in acidification and alkalinization are attributed to spatially variable biological processes in the upper ocean and horizontal and vertical physical redistribution of DIC. Our model and observational results have implications for the spatial extent and pattern of ocean acidification, along with the strength of the ocean carbon sink, which are key aspects of global climate change.

Long-term variation in dissolved inorganic carbon and ocean acidification indices in the Northwest Pacific from 1993 to 2018: A study of a biogeochemical model with an operational ocean model product and observational evidence

2021 ◽  
Author(s):  
Miho Ishizu ◽  
Yasumasa Miyazawa ◽  
Xinyu Guo
Keyword(s):  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Kuroshio Extension ◽  
Vertical Mixing ◽  
Ocean Model ◽  
Biogeochemical Model ◽  
Northwest Pacific ◽  
Subarctic Region ◽  
Surface Ocean

Abstract The multi-decadal variation in ocean acidification indices in the Northwest Pacific was examined using a biogeochemical model with an operational ocean model product for the period 1993–2018. We found that ocean acidification varied regionally in the Northwest Pacific. The surface ocean (above 100 m depth) underwent acidification that progressed more quickly in the subtropical region and the Kuroshio extension than in the subarctic region due to vertical mixing of the dissolved inorganic carbon (DIC) supply exceeding DIC release by air–sea exchange. Below 100 m depth, acidification and alkalinization occurred in the subtropical and subarctic regions, respectively. We attribute these regional differences in acidification and alkalinization to spatially variable biological processes in the upper layer and physical redistribution of DIC, both horizontally and vertically.

scholarly journals Beyond burial: lateral exchange is a significant atmospheric carbon sink in mangrove forests

2018 ◽  
Vol 14 (7) ◽  
pp. 20180200 ◽  
Author(s):  
Damien T. Maher ◽  
Mitchell Call ◽  
Isaac R. Santos ◽  
Christian J. Sanders
Keyword(s):  
Organic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sink ◽  
Blue Carbon ◽  
Mangrove Forests ◽  
Carbon Framework ◽  
Sequestration Potential ◽  
Seagrass Ecosystems ◽  
Atmospheric Carbon

The blue carbon paradigm has evolved in recognition of the high carbon storage and sequestration potential of mangrove, saltmarsh and seagrass ecosystems. However, fluxes of the potent greenhouse gases CH 4 and N 2 O, and lateral export of carbon are often overlooked within the blue carbon framework. Here, we show that the export of dissolved inorganic carbon (DIC) and alkalinity is approximately 1.7 times higher than burial as a long-term carbon sink in a subtropical mangrove system. Fluxes of methane offset burial by approximately 6%, while the nitrous oxide sink was approximately 0.5% of burial. Export of dissolved organic carbon and particulate organic carbon to the coastal zone is also significant and combined may account for an atmospheric carbon sink similar to burial. Our results indicate that the export of DIC and alkalinity results in a long-term atmospheric carbon sink and should be incorporated into the blue carbon paradigm when assessing the role of these habitats in sequestering carbon and mitigating climate change.

Variation of Surface Radiocarbon in the North Pacific During Summer Season 2004–2016

Radiocarbon ◽  
2019 ◽  
Vol 61 (5) ◽  
pp. 1367-1375 ◽  
Author(s):  
T Aramaki ◽  
S Nakaoka ◽  
Y Terao ◽  
S Kushibashi ◽  
T Kobayashi ◽  
...  
Keyword(s):  
North Pacific ◽  
Kuroshio Extension ◽  
Deep Convection ◽  
Subtropical Region ◽  
Subarctic Region ◽  
Surface Ocean ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

ABSTRACTSurface radiocarbon (Δ14C) in the North Pacific has been monitored using a commercial volunteer observation ship since the early 2000s. Here we report the temporal and spatial variations in Δ14C in the summer surface water when the surface ocean is vertically stratified over a 13-yr period, 2004–2016. The long-term Δ14C decreasing trend after the late 1970s in the subtropical region has continued to the present and the rate of decrease of the Kuroshio and Kuroshio Extension, North Pacific and California current areas is calculated to be –3.3, –5.2 and –3.3 ‰/yr, respectively. After 2012 the Δ14C of the Kuroshio and Kuroshio Extension area, however, has remained at an approximately constant value of around 50‰. The result may indicate that subtropical surface Δ14C in the western North Pacific has reached an equilibrium with atmospheric Δ14CO2. The Δ14C in the subarctic region is markedly lower than values in the subtropical region and it seems that the decreasing tendency of surface Δ14C has changed to an increasing tendency after 2010. The results may indicate that bomb-produced 14C, which has accumulated below the mixed layer in the past few decades, has been entrained into the surface layer by deep convection.

Recent trends in air-sea CO2 fluxes and ocean acidification in the Arabian Sea

2021 ◽  
Author(s):  
Zouhair Lachkar ◽  
Michael Mehari ◽  
Alain De Verneil ◽  
Marina Lévy ◽  
Shafer Smith
Keyword(s):  
Ocean Acidification ◽  
Arabian Sea ◽  
Coastal Upwelling ◽  
Biogeochemical Model ◽  
Atmospheric Concentration ◽  
Physical Forcing ◽  
Freshwater Fluxes ◽  
Ocean Biogeochemical Model ◽  
Long Term Trends

&lt;p&gt;Recent observations and modeling evidence indicate that the Arabian Sea (AS) is a net source of carbon to the atmosphere. Yet, the interannual variability modulating the air-sea CO&lt;sub&gt;2&lt;/sub&gt; fluxes in the region, as well as their long-term trends, remain poorly known. Furthermore, while the rising atmospheric concentration of CO&lt;sub&gt;2&lt;/sub&gt; is causing surface ocean pH to drop globally, little is known about local and regional acidification trends in the AS, a region hosting a major coastal upwelling system naturally prone to relatively low surface pH. Here, we simulate the evolution of air-sea CO&lt;sub&gt;2&lt;/sub&gt; fluxes and reconstruct the progression of ocean acidification in the AS from 1982 through 2019 using an eddy-resolving ocean biogeochemical model covering the full Indian Ocean and forced with observation-based winds and heat and freshwater fluxes. Additionally, using a set of sensitivity simulations that vary in terms of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; levels and physical forcing we quantify the variability of fluxes associated with both natural and anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; and disentangle the contributions of climate variability and that of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentrations to the long-term trends in air-sea CO&lt;sub&gt;2&lt;/sub&gt; fluxes and acidification. Our analysis reveals a strong variability in the air-sea CO&lt;sub&gt;2&lt;/sub&gt; fluxes and pH on a multitude of timescales ranging from the intra-seasonal to the decadal. Furthermore, a strong progression of ocean acidification with an important penetration into the thermocline is simulated locally near the upwelling regions. Our analysis also indicates that in addition to the increasing anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; concentrations in the atmosphere, recent warming and monsoon wind changes have substantially modulated these trends regionally.&lt;/p&gt;

Long-term variation of characteristics of local land atmosphere coupling over TP and the possible influence of Southern Asian Monsoon

2021 ◽  
Author(s):  
Genhou Sun ◽  
Zeyong Hu ◽  
yaoming Ma ◽  
Zhipeng Xie ◽  
Wei Wei ◽  
...  
Keyword(s):  
Observational Data ◽  
Asian Monsoon ◽  
Energy Budgets ◽  
Annual Variations ◽  
Term Variation ◽  
Close Relationship ◽  
The Relationship ◽  
Diagram Analysis ◽  
Long Term Variations

&lt;p&gt;This study investigates the long-term variations of local land atmosphere coupling (LoCo) over Tibetan Plateau (TP) by applying a mixing diagram to the observational data at six stations over TP and ERA5 and the possible influence of Southern Asian monsoon. The result indicates that the monthly-mean daily variation in T&lt;sub&gt;2m&lt;/sub&gt;, q&lt;sub&gt;2m&lt;/sub&gt;, H&lt;sub&gt;sfc,&lt;/sub&gt; and LE&lt;sub&gt;sfc&lt;/sub&gt; at Nyingchi, Nagqu, Nam Co, Qomolangma, Ngari, and Muztagata in ERA5 are close to those in observational data. Comparison of mixing diagram analysis using the monthly-mean variables of ERA5 and the observational data indicates ERA5 could provide reliable information of LoCo at six stations. The relationships between H&lt;sub&gt;sfc&lt;/sub&gt; and daytime PBLH, and the variations of LCL deficit at six stations are different due to the differences in the soil states. The long-term variations in the PBL energy budgets, mean daytime PBLH, and LCL deficits at 31&lt;sup&gt;&amp;#9702;&lt;/sup&gt;N and 90&lt;sup&gt;&amp;#9702;&lt;/sup&gt;E show clear annual variations and have a close relationship between Southern Asian monsoon. The possible influence of the Southern Asian monsoon is also discussed in terms of the relationship between the Webster-Yang index and the PBL energy budgets, mean PBLH and mean LCL over TP.&lt;/p&gt;

scholarly journals Arctic Ocean Freshwater Changes over the Past 100 Years and Their Causes

2008 ◽  
Vol 21 (2) ◽  
pp. 364-384 ◽  
Author(s):  
I. V. Polyakov ◽  
V. A. Alexeev ◽  
G. I. Belchansky ◽  
I. A. Dmitrenko ◽  
V. V. Ivanov ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Observational Data ◽  
Thermohaline Circulation ◽  
Atmospheric Precipitation ◽  
The Arctic ◽  
Central Basin ◽  
Central Arctic Ocean ◽  
The Arctic Ocean ◽  
Long Term Variations

Abstract Recent observations show dramatic changes of the Arctic atmosphere–ice–ocean system. Here the authors demonstrate, through the analysis of a vast collection of previously unsynthesized observational data, that over the twentieth century the central Arctic Ocean became increasingly saltier with a rate of freshwater loss of 239 ± 270 km3 decade−1. In contrast, long-term (1920–2003) freshwater content (FWC) trends over the Siberian shelf show a general freshening tendency with a rate of 29 ± 50 km3 decade−1. These FWC trends are modulated by strong multidecadal variability with sustained and widespread patterns. Associated with this variability, the FWC record shows two periods in the 1920s–30s and in recent decades when the central Arctic Ocean was saltier, and two periods in the earlier century and in the 1940s–70s when it was fresher. The current analysis of potential causes for the recent central Arctic Ocean salinification suggests that the FWC anomalies generated on Arctic shelves (including anomalies resulting from river discharge inputs) and those caused by net atmospheric precipitation were too small to trigger long-term FWC variations in the central Arctic Ocean; to the contrary, they tend to moderate the observed long-term central-basin FWC changes. Variability of the intermediate Atlantic Water did not have apparent impact on changes of the upper–Arctic Ocean water masses. The authors’ estimates suggest that ice production and sustained draining of freshwater from the Arctic Ocean in response to winds are the key contributors to the salinification of the upper Arctic Ocean over recent decades. Strength of the export of Arctic ice and water controls the supply of Arctic freshwater to subpolar basins while the intensity of the Arctic Ocean FWC anomalies is of less importance. Observational data demonstrate striking coherent long-term variations of the key Arctic climate parameters and strong coupling of long-term changes in the Arctic–North Atlantic climate system. Finally, since the high-latitude freshwater plays a crucial role in establishing and regulating global thermohaline circulation, the long-term variations of the freshwater content discussed here should be considered when assessing climate change and variability.

scholarly journals MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies

2013 ◽  
Vol 6 (1) ◽  
pp. 1259-1365 ◽  
Author(s):  
A. Yool ◽  
E. E. Popova ◽  
T. R. Anderson
Keyword(s):  
Carbon Cycle ◽  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
World Ocean ◽  
Ecosystem Dynamics ◽  
Full Description ◽  
Biogeochemical Model ◽  
Intermediate Complexity ◽  
Nutrient Utilisation

Abstract. MEDUSA-1.0 (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification) was developed as an "intermediate complexity" plankton ecosystem model to study the biogeochemical response, and especially that of the so-called "biological pump", to anthropogenically-driven change in the World Ocean (Yool et al., 2011). The base currency in this model was nitrogen from which fluxes of organic carbon, including export to the deep ocean, were calculated by invoking fixed C:N ratios in phytoplankton, zooplankton and detritus. Since the beginning of the industrial era, the atmospheric concentration of carbon dioxide (CO2) has significantly increased above its natural, inter-glacial background concentration. Simulating and predicting the carbon cycle in the ocean in its entirety, including ventilation of CO2 with the atmosphere and the resulting impact of ocean acidification on marine ecosystems, therefore requires that both organic and inorganic carbon be afforded a full representation in the model specification. Here, we introduce MEDUSA-2.0, an expanded successor model which includes additional state variables for dissolved inorganic carbon, alkalinity, dissolved oxygen and detritus carbon (permitting variable C:N in exported organic matter), as well as a simple benthic formulation and extended parameterisations of phytoplankton growth, calcification and detritus remineralisation. A full description of MEDUSA-2.0, including its additional functionality, is provided and a multi-decadal hindcast simulation described (1860–2005), to evaluate the biogeochemical performance of the model.

scholarly journals The continued accumulation of anthropogenic carbon in the global ocean during the 2010s

2021 ◽  
Author(s):  
Jens Daniel Müller ◽  
Donghe Zhu ◽  
Luke Gregor ◽  
Are Olsen ◽  
Nico Lange ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sink ◽  
Synthetic Data ◽  
Uncertainty Assessment ◽  
Global Ocean ◽  
Coupled Analysis ◽  
Biogeochemical Model ◽  
Linear Regression Models ◽  
The Past

&lt;p&gt;Surface ocean pCO&lt;sub&gt;2&lt;/sub&gt;-based estimates and models indicate that the ocean sink for anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; (C&lt;sub&gt;ant&lt;/sub&gt;) has continued to increase unabatedly over the past decade. However, the most recent global and observation-based estimate of the accumulation of C&lt;sub&gt;ant&lt;/sub&gt; in the ocean interior by Gruber et al. (2019) does not extend beyond 2007, preventing an independent assessment of this increase in the magnitude of the sink.&lt;/p&gt;&lt;p&gt;Here, we exploit about 50,000 additional observations of dissolved inorganic carbon (DIC) and other relevant biogeochemical parameters, to extend the Gruber et al. analysis based on the eMLR(C*) method to the 2010s. These data were collected from all major ocean basins over the past decade by GO-SHIP and associated programs, and assembled through GLODAPv2.2020 into an internally consistent data product. We refine the eMLR(C*) method in three ways to achieve the updated storage estimates: (1) the uncertainty assessment is improved, based on a coupled analysis of observations and synthetic data generated from an ocean biogeochemical model, (2) the robustness of the multiple linear regression models is increased, using more stringent predictor and model selection procedures, and (3) the mapping of the C&lt;sub&gt;ant&lt;/sub&gt; fields relies on a MLR ensemble approach that takes into account co-occurring temporal changes of the predictor variables salinity, temperature and oxygen.&lt;/p&gt;&lt;p&gt;&lt;br&gt;Initial results show that the ocean has continued to act as a strong C&lt;sub&gt;ant&lt;/sub&gt; sink with an average uptake rate of 2.8 &amp;#177; 0.3 Pg C yr&lt;sup&gt;-1&lt;/sup&gt; between the reference years 2007 and 2015. This represents a small increase in rate compared to 2.6 &amp;#177; 0.3 Pg C yr&lt;sup&gt;-1&lt;/sup&gt; determined for the 1994 through 2007 period. This increase is slightly smaller than expected on the basis of the growth of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; over the period, but associated uncertainties are too large to make a conclusive statement about whether the ocean carbon sink is slowing down. Initial analyses of the synthetic data indicate that variable ocean circulation and limited sampling, especially the small number of cruises in the Indian Ocean, represent the biggest sources of uncertainty for the eMLR(C*)-based estimate. However, our preliminary sink estimate is in good agreement with recent air-sea CO&lt;sub&gt;2&lt;/sub&gt; flux-based uptake estimates, based on an ensemble of surface pCO&lt;sub&gt;2&lt;/sub&gt; interpolation techniques once these fluxes are adjusted for the river carbon input driven outgassing of natural CO&lt;sub&gt;2&lt;/sub&gt;.&lt;/p&gt;

scholarly journals Coral calcification mechanisms facilitate adaptive responses to ocean acidification

2017 ◽  
Vol 284 (1868) ◽  
pp. 20172117 ◽  
Author(s):  
Verena Schoepf ◽  
Christopher P. Jury ◽  
Robert J. Toonen ◽  
Malcolm T. McCulloch
Keyword(s):  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Coral Species ◽  
Dissolved Inorganic Carbon ◽  
Adaptive Responses ◽  
Natural Gradient ◽  
Coral Calcification ◽  
Seawater Ph ◽  
Two Temperatures

Ocean acidification (OA) is a pressing threat to reef-building corals, but it remains poorly understood how coral calcification is inhibited by OA and whether corals could acclimatize and/or adapt to OA. Using a novel geochemical approach, we reconstructed the carbonate chemistry of the calcifying fluid in two coral species using both a pH and dissolved inorganic carbon (DIC) proxy (δ 11 B and B/Ca, respectively). To address the potential for adaptive responses, both species were collected from two sites spanning a natural gradient in seawater pH and temperature, and then subjected to three pH T levels (8.04, 7.88, 7.71) crossed by two temperatures (control, +1.5°C) for 14 weeks. Corals from the site with naturally lower seawater pH calcified faster and maintained growth better under simulated OA than corals from the higher-pH site. This ability was consistently linked to higher pH yet lower DIC values in the calcifying fluid, suggesting that these differences are the result of long-term acclimatization and/or local adaptation to naturally lower seawater pH. Nevertheless, all corals elevated both pH and DIC significantly over seawater values, even under OA. This implies that high pH upregulation combined with moderate levels of DIC upregulation promote resistance and adaptive responses of coral calcification to OA.

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