scholarly journals Ocean acidification from 1997 to 2011 in the subarctic western North Pacific Ocean

2013 ◽  
Vol 10 (12) ◽  
pp. 7817-7827 ◽  
Author(s):  
M. Wakita ◽  
S. Watanabe ◽  
M. Honda ◽  
A. Nagano ◽  
K. Kimoto ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Mixed Layer ◽  
North Pacific ◽  
Dissolved Inorganic Carbon ◽  
North Pacific Ocean ◽  
Total Alkalinity ◽  
Co2 Uptake ◽  
The North ◽  
Western Subarctic Gyre ◽  
Calcite Saturation

Abstract. Rising atmospheric CO2 contents have led to greater CO2 uptake by the oceans, lowering both pH due to increasing hydrogen ions and CaCO3 saturation states due to declining carbonate ion (CO32−). Here we used previously compiled data sets and new data collected in 2010 and 2011 to investigate ocean acidification of the North Pacific western subarctic gyre. In winter, the western subarctic gyre is a source of CO2 to the atmosphere because of convective mixing of deep waters rich in dissolved inorganic carbon (DIC). We calculated pH in winter mixed layer from DIC and total alkalinity (TA), and found that it decreased at the rate of −0.0011 ± 0.0004 yr−1 from 1997 to 2011. This decrease rate is slower than that expected under the condition of seawater/atmosphere equilibration, and it is also slower than the rate in the subtropical regions (−0.002 yr−1). The slow rate is caused by a reduction of CO2 emission in winter due to an increase in TA. Below the mixed layer, the calcite saturation horizon (~ 185 m depth) shoaled at the rate of 2.9 ± 0.9 m yr−1 as the result of the declining CO32− concentration (−0.03 ± 0.01 μmol kg−1 yr−1). Between 200 m and 300 m depth, pH decline during the study period (−0.0051 ± 0.0010 yr−1) was larger than ever reported in the open North Pacific. This enhanced acidification rate below the calcite saturation horizon reflected not only the uptake of anthropogenic CO2 but also the increase in the decomposition of organic matter evaluated from the increase in AOU, which suggests that the dissolution of CaCO3 particles increased.

scholarly journals Ocean acidification from 1997 to 2011 in the subarctic western North Pacific Ocean

2013 ◽  
Vol 10 (5) ◽  
pp. 8283-8311 ◽  
Author(s):  
M. Wakita ◽  
S. Watanabe ◽  
M. Honda ◽  
A. Nagano ◽  
K. Kimoto ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Mixed Layer ◽  
North Pacific ◽  
Dissolved Inorganic Carbon ◽  
North Pacific Ocean ◽  
Total Alkalinity ◽  
Co2 Uptake ◽  
The North ◽  
Western Subarctic Gyre ◽  
Calcite Saturation

Abstract. Rising atmospheric CO2 contents have led to greater CO2 uptake by the oceans, lowering both pH due to increasing hydrogen ions and CaCO3 saturation states due to declining carbonate ion (CO32−). Here, we used previously compiled data sets and new data collected in 2010 and 2011 to investigate ocean acidification of the North Pacific western subarctic gyre. In winter, the western subarctic gyre is a source of CO2 to the atmosphere because of convective mixing of deep waters rich in dissolved inorganic carbon (DIC). We calculated pH in winter mixed layer from DIC and total alkalinity (TA), and found that it decreased at the rate of −0.001 ± 0.0004 yr−1 from 1997 to 2011. This decrease rate is slower than that expected under condition of seawater/atmosphere equilibration, and it is also slower than the rate in the subtropical regions (−0.002 yr−1). The slow rate is caused by a reduction of CO2 emission in winter due to an increase in TA. Below the mixed layer, the calcite saturation horizon (~185 m depth) shoaled at the rate of 2.9 ± 0.9 m yr−1 as the result of the declining CO32− concentration (−0.03 ± 0.01 μmol k−1yr−1). Between 200 m and 300 m depth, pH decline during the study period (−0.0051 ± 0.0010 yr−1) was larger than ever reported in the open North Pacific. This enhanced acidification rate below the calcite saturation horizon reflected not only the uptake of anthropogenic CO2 but also the increase in the decomposition of organic matter evaluated from the increase in AOU, which suggests that the dissolution of CaCO3 particles increased.

scholarly journals Quantifying the influence of CO<sub>2</sub> seasonality on future ocean acidification

2015 ◽  
Vol 12 (8) ◽  
pp. 5907-5940
Author(s):  
T. P. Sasse ◽  
B. I. McNeil ◽  
R. J. Matear ◽  
A. Lenton
Keyword(s):  
Ocean Acidification ◽  
North Pacific ◽  
Dissolved Inorganic Carbon ◽  
Marine Ecosystem ◽  
Global Ocean ◽  
Saturation State ◽  
The North ◽  
Data Limitations ◽  
The Future ◽  
The North Pacific

Abstract. Ocean acidification is a predictable consequence of rising atmospheric carbon dioxide (CO2), and is highly likely to impact the entire marine ecosystem – from plankton at the base to fish at the top. Factors which are expected to be impacted include reproductive health, organism growth and species composition and distribution. Predicting when critical threshold values will be reached is crucial for projecting the future health of marine ecosystems and for marine resources planning and management. The impacts of ocean acidification will be first felt at the seasonal scale, however our understanding how seasonal variability will influence rates of future ocean acidification remains poorly constrained due to current model and data limitations. To address this issue, we first quantified the seasonal cycle of aragonite saturation state utilizing new data-based estimates of global ocean surface dissolved inorganic carbon and alkalinity. This seasonality was then combined with earth system model projections under different emissions scenarios (RCPs 2.6, 4.5 and 8.5) to provide new insights into future aragonite under-saturation onset. Under a high emissions scenario (RCP 8.5), our results suggest accounting for seasonality will bring forward the initial onset of month-long under-saturation by 17 years compared to annual-mean estimates, with differences extending up to 35 ± 17 years in the North Pacific due to strong regional seasonality. Our results also show large-scale under-saturation once atmospheric CO2 reaches 486 ppm in the North Pacific and 511 ppm in the Southern Ocean independent of emission scenario. Our results suggest that accounting for seasonality is critical to projecting the future impacts of ocean acidification on the marine environment.

scholarly journals Development of a Biogeochemical and Carbon Model Related to Ocean Acidification Indices with an Operational Ocean Model Product in the North Western Pacific

2019 ◽  
Vol 11 (9) ◽  
pp. 2677 ◽  
Author(s):  
Miho Ishizu ◽  
Yasumasa Miyazawa ◽  
Tomohiko Tsunoda ◽  
Xinyu Guo
Keyword(s):  
Ocean Acidification ◽  
General Circulation ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Ocean Model ◽  
Western Pacific ◽  
Total Alkalinity ◽  
The North ◽  
North Western ◽  
North Western Pacific

We developed a biogeochemical and carbon model (JCOPE_EC) coupled with an operational ocean model for the North Western Pacific. JCOPE_EC represents ocean acidification indices on the background of the risks due to ocean acidification and our model experiences. It is an off-line tracer model driven by a high-resolution regional ocean general circulation model (JCOPE2M). The results showed that the model adequately reproduced the general patterns in the observed data, including the seasonal variability of chlorophyll-a, dissolved inorganic nitrogen/phosphorus, dissolved inorganic carbon, and total alkalinity. We provide an overview of this system and the results of the model validation based on the available observed data. Sensitivity analysis using fixed values for temperature, salinity, dissolved inorganic carbon and total alkalinity helped us identify which variables contributed most to seasonal variations in the ocean acidification indices, pH and Ωarg. The seasonal variation in the pHinsitu was governed mainly by balances of the change in temperature and dissolved inorganic carbon. The seasonal increase in Ωarg from winter to summer was governed mainly by dissolved inorganic carbon levels.

scholarly journals Role of North Pacific Mixed Layer in the Response of SST Annual Cycle to Global Warming

2015 ◽  
Vol 28 (23) ◽  
pp. 9451-9458 ◽  
Author(s):  
Changlin Chen ◽  
Guihua Wang
Keyword(s):  
Global Warming ◽  
Mixed Layer ◽  
Annual Cycle ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Mixed Layer Depth ◽  
Ecological Impacts ◽  
Global Ocean ◽  
The North ◽  
The North Pacific

Abstract The annual cycle of sea surface temperature (SST) in the North Pacific Ocean is examined in terms of its response to global warming based on climate model simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). As the global ocean warms up, the SST in the North Pacific generally tends to increase and the warming is greater in summer than in winter, leading to a significant intensification of SST annual cycle. The mixed layer temperature equation is used to examine the mechanism of this intensification. Results show that the decrease of mixed layer depth (MLD) in summer is the main reason behind the intensification of SST annual cycle. Because the MLD in summer is much shallower than that in winter, the incoming net heat flux is trapped in a thinner surface layer in summer, causing a warmer summer SST and the amplification of SST annual cycle. The change of the SST annual cycle in the North Pacific may have profound ecological impacts.

scholarly journals Vertically migrating phytoplankton drive seasonal formation of subsurface negative preformed nitrate anomalies in the subtropical North Pacific and North Atlantic

2018 ◽  
Author(s):  
Robert T. Letscher ◽  
Tracy A. Villareal
Keyword(s):  
Organic Matter ◽  
Mixed Layer ◽  
North Atlantic ◽  
North Pacific ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Euphotic Zone ◽  
The North ◽  
Station Aloha ◽  
Biological Nitrogen

Abstract. Summertime drawdown of dissolved inorganic carbon in the absence of measurable nutrients from the mixed layer and subsurface negative preformed nitrate (preNO3) anomalies observed for the ocean's subtropical gyres are two biogeochemical phenomena that have thus far eluded complete description. Many processes are thought to contribute including biological nitrogen fixation, lateral nutrient transport, carbon overconsumption or non-Redfield C : N : P organic matter cycling, heterotrophic nutrient uptake, and the actions of vertically migrating phytoplankton. Here we investigate the seasonal formation rates and potential contributing mechanisms for negative preformed nitrate anomalies (oxygen consumption without stoichiometric nitrate release) in the subsurface and positive preformed nitrate anomalies (oxygen production without stoichiometric nitrate drawdown) in the euphotic zone at the subtropical ocean time series stations ALOHA in the North Pacific and BATS in the North Atlantic. Non-Redfield −O2 : N stoichiometry for dissolved organic matter (DOM) remineralization is found to account for up to ~ 15 mmol N m−2 yr−1 of negative preNO3 anomaly formation at both stations. Residual negative preNO3 anomalies in excess of that which can be accounted for by non-Redfield DOM cycling are found to accumulate at a rate of ~ 32–46 mmol N m−2 yr−1 at station ALOHA and ~ 46–87 mmol N m−2 yr−1 at the BATS station. These negative anomaly formation rates are in approximate balance with positive preNO3 anomaly formation rates from the euphotic zone located immediately above the nutricline in the water column. Cycling of transparent exopolymer particles (TEP) and heterotrophic nitrate uptake can contribute to the formation of these preNO3 anomalies, however a significant fraction, estimated at ~ 50–95 %, is unexplained by the sum of these processes. Vertically migrating phytoplankton possess the necessary nutrient acquisition strategy and biogeochemical signature to quantitatively explain both the residual negative and positive preNO3 anomalies as well as the mixed layer dissolved inorganic carbon drawdown at stations ALOHA and BATS. TEP production by the model Rhizosolenia mat system could provide accelerated vertical transport of TEP as well as link the three processes together. Phytoplankton vertical migrators, although rare and easily overlooked, may play a large role in subtropical ocean nutrient cycling and the biological pump.

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