Posts Tagged 'regionalmodeling'

Model constraints on the anthropogenic carbon budget of the Arctic Ocean

The Arctic Ocean is projected to experience not only amplified climate change but also amplified ocean acidification. Modeling future acidification depends on our ability to simulate baseline conditions and changes over the industrial era. Such centennial-scale changes require a global model to account for exchange between the Arctic and surrounding regions. Yet the coarse resolution of typical global models may poorly resolve that exchange as well as critical features of Arctic Ocean circulation. Here we assess how simulations of Arctic Ocean storage of anthropogenic carbon (Cant), the main driver of open- ocean acidification, differ when moving from coarse to eddy admitting resolution in a global ocean circulation-biogeochemistry model (NEMO-PISCES). The Arctic’s regional storage of Cant is enhanced as model resolution increases. While the coarse- resolution model configuration ORCA2 (2°) stores 2.0 Pg C in the Arctic Ocean between 1765 and 2005, the eddy-admitting versions ORCA05 and ORCA025 (1/2° and 1/4°) store 2.4 and 2.6 Pg C. That result from ORCA025 falls within the uncertainty range from a previous data-based Cant storage estimate (2.5 to 3.3 Pg C). Yet those limits may each need to be reduced by about 10 % because data-based Cant concentrations in deep waters remain at ∼ 6 μmol kg−1, while they should be almost negligible by analogy to the near-zero observed CFC-12 concentrations from which they are calculated. Across the three resolutions, there was roughly three times as much anthropogenic carbon that entered the Arctic Ocean through lateral transport than via the flux of CO2 across the air-sea interface. Wider comparison to nine earth system models that participated in the Coupled Model Intercomparison Project Phase 5 (CMIP5) reveals much larger diversity of stored anthropogenic carbon and lateral transport. Only the CMIP5 models with higher lateral transport obtain Cant inventories that are close to the data-based estimates. Increasing resolution also enhances acidification, e.g., with greater shoaling of the Arctic’s average depth of the aragonite saturation horizon during 1960–2012, from 50 m in ORCA2 to 210 m in ORCA025. To assess the potential to further refine modeled estimates of the Arctic Ocean’s Cant storage and acidification, sensitivity tests that adjust model parameters are needed given that century-scale global ocean biogeochemical simulations still cannot be run routinely at high resolution.

Continue reading ‘Model constraints on the anthropogenic carbon budget of the Arctic Ocean’

Consequences of spatially variable ocean acidification in the California Current: lower pH drives strongest declines in benthic species in southern regions while greatest economic impacts occur in northern regions

Highlights

• Impacts of ocean acidification change with latitude in the California Current.
• Vulnerable species (e.g., calcifying invertebrates) and their predators decline most.
• Decline in revenue projected, mainly from lower Dungeness crab catch in the north.
Abstract

Marine ecosystems are experiencing rapid changes driven by anthropogenic stressors which, in turn, are affecting human communities. One such stressor is ocean acidification, a result of increasing carbon emissions. Most research on biological impacts of ocean acidification has focused on the responses of an individual species or life stage. Yet, understanding how changes scale from species to ecosystems, and the services they provide, is critical to managing fisheries and setting research priorities. Here we use an ecosystem model, which is forced by oceanographic projections and also coupled to an economic input-output model, to quantify biological responses to ocean acidification in six coastal regions from Vancouver Island, Canada to Baja California, Mexico and economic responses at 17 ports on the US west coast. This model is intended to explore one possible future of how ocean acidification may influence this coastline. Outputs show that declines in species biomass tend to be larger in the southern region of the model, but the largest economic impacts on revenue, income and employment occur from northern California to northern Washington State. The economic consequences are primarily driven by declines in Dungeness crab from loss of prey. Given the substantive revenue generated by the fishing industry on the west coast, the model suggests that long-term planning for communities, researchers and managers in the northern region of the California Current would benefit from tracking Dungeness crab productivity and potential declines related to pH.

Continue reading ‘Consequences of spatially variable ocean acidification in the California Current: lower pH drives strongest declines in benthic species in southern regions while greatest economic impacts occur in northern regions’

Acidification at the surface in the East Sea: a coupled climate-carbon cycle model study

This modeling study investigates the impacts of increasing atmospheric CO2 concentration on acidification in the East Sea. A historical simulation for the past three decades (1980 to 2010) was performed using the Hadley Centre Global Environmental Model (version 2), a coupled climate model with atmospheric, terrestrial and ocean cycles. As the atmospheric CO2 concentration increased, acidification progressed in the surface waters of the marginal sea. The acidification was similar in magnitude to observations and models of acidification in the global ocean. However, in the global ocean, the acidification appears to be due to increased in-situ oceanic CO2 uptake, whereas local processes had stronger effects in the East Sea. pH was lowered by surface warming and by the influx of water with higher dissolved inorganic carbon (DIC) from the northwestern Pacific. Due to the enhanced advection of DIC, the partial pressure of CO2 increased faster than in the overlying air; consequently, the in-situ oceanic uptake of CO2 decreased.

Continue reading ‘Acidification at the surface in the East Sea: a coupled climate-carbon cycle model study’

Climate change impacts on natural sulfur production: ocean acidification and community shifts

Utilizing the reduced-complexity model Hector, a regional scale analysis was conducted quantifying the possible effects climate change may have on dimethyl sulfide (DMS) emissions within the oceans. The investigation began with a review of the sulfur cycle in modern Earth system models. We then expanded the biogeochemical representation within Hector to include a natural ocean component while accounting for acidification and planktonic community shifts. The report presents results from both a latitudinal and a global perspective. This new approach highlights disparate outcomes which have been inadequately characterized via planetary averages in past publications. Our findings suggest that natural sulfur emissions (ESN) may exert a forcing up to 4 times that of the CO2 marine feedback, 0.62 and 0.15 Wm−2, respectively, and reverse the radiative forcing sign in low latitudes. Additionally, sensitivity tests were conducted to demonstrate the need for further examination of the DMS loop. Ultimately, the present work attempts to include dynamic ESN within reduced-complexity simulations of the sulfur cycle, illustrating its impact on the global radiative budget.

Continue reading ‘Climate change impacts on natural sulfur production: ocean acidification and community shifts’

Rapid changes in anthropogenic carbon storage and ocean acidification in the intermediate layers of the Eurasian Arctic Ocean: 1996‐2015

The extended multiple linear regression (eMLR) technique is used to determine changes in anthropogenic carbon in the intermediate layers of the Eurasian Basin based on occupations from four cruises between 1996 and 2015. The results show a significant increase in basin‐wide anthropogenic carbon storage in the Nansen Basin (0.44‐0.73 ± 0.14 mol C m−2 yr−1) and the Amundsen Basin (0.63‐1.04 ± 0.09 mol C m−2 yr−1). Over the last two decades, inferred changes in ocean acidification (0.020‐0.055 pH units) and calcium carbonate desaturation (0.05‐0.18 units) are pronounced and rapid. These results, together with results from carbonate‐dynamic box model simulations and 129I tracer distribution simulations, suggest that the accumulation of anthropogenic carbon in the intermediate layers of the Eurasian Basin are consistent with increasing concentrations of anthropogenic carbon in source waters of Atlantic origin entering the Arctic Ocean followed by interior transport. The dissimilar distributions of anthropogenic carbon in the interior Nansen and Amundsen Basins are likely due to differences in the lateral ventilation of the intermediate layers by the return flows and ramifications of the boundary current along the topographic boundaries in the Eurasian Basin.

Continue reading ‘Rapid changes in anthropogenic carbon storage and ocean acidification in the intermediate layers of the Eurasian Arctic Ocean: 1996‐2015’

Treated wastewater changes the export of dissolved inorganic carbon and its isotopic composition and leads to acidification in coastal oceans

Human-induced changes to carbon fluxes across the land-ocean interface can influence the global carbon cycle, yet the impacts of rapid urbanization and establishment of wastewater treatment plants (WWTPs) on coastal ocean carbon cycles are poorly known. This is unacceptable as at present ~64% of global municipal wastewater is treated before discharge. Here, we report surface water dissolved inorganic carbon (DIC) and sedimentary organic carbon concentrations and their isotopic compositions in the rapidly urbanized Jiaozhou Bay in northeast China as well as carbonate parameters in effluents of three large WWTPs around the bay. Using DIC, δ13CDIC and total alkalinity (TA) data and a tracer model, we determine the contributions to DIC from wastewater DIC input, net community production, calcium carbonate precipitation and CO2 outgassing. Our study shows that high-DIC and low-pH wastewater effluent represents an important source of DIC and acidification in coastal waters. In contrast to the traditional view of anthropogenic organic carbon export and degradation, we suggest that with the increase of wastewater discharge and treatment rates, wastewater DIC input may play an increasingly more important role in the coastal ocean carbon cycle.

Continue reading ‘Treated wastewater changes the export of dissolved inorganic carbon and its isotopic composition and leads to acidification in coastal oceans’

The spatial and temporal variability of air-sea CO2 fluxes and the effect of net coral reef calcification in the Indonesian Seas: a numerical sensitivity study

A numerical model system was developed and applied to simulate air-sea fluxes of CO2 and coral reef calcification in the Indonesian Seas and adjacent ocean basin for the period 1960–2014 on a fine resolution grid (ca. 11 km) in order to study their response to rising sea water temperatures and CO2 concentrations in the atmosphere. Results were analyzed for different sub-regions on the Sunda Shelf (Gulf of Thailand, Malacca Strait, Java Sea) and show realistic and different levels, signs and pronounced temporal variability in air-sea CO2 flux. The Gulf of Thailand changes from an atmospheric CO2 sink during the boreal winter to a CO2 source in summer due to higher water temperatures, while other sub-regions as well as the entire averaged Sunda Shelf act as a continuous source of CO2 for the atmosphere. However, increasing atmospheric CO2 concentrations weakened this source function during the simulation period. In 2007, the model simulations showed even a first flux inversion, in course of which the Java Sea took up CO2. The simulated trends suggest that the entire Sunda Shelf will turn into a permanent sink for atmospheric CO2 within the next 30–35 years if current trends remain constant. Considering the period between 2010 and 2014, coral reef calcification enhanced the average CO2 emission of the Sunda Shelf by more than 10% from 15 to 17 Tg C yr−1 due to lowering the pH and increasing the partial pressure of CO2 in surface water. During the entire period of simulation, net reef calcification decreased although increasing seawater temperature mitigated effects of reduced CO2 emission and the resulting decrease of the pH values on reef calcification. Our realistic simulation results already without consideration of any biological processes suggest that biological processes taking up and releasing CO2 are currently well balanced in these tropical regions. However, the counteracting effects of climate change on the reef calcification, on other biological processes and the carbonate system need to be investigated in more detail. SST increased by about 0.6°C during the last 55 years, while SSS decreased by about 0.7 psu.

Continue reading ‘The spatial and temporal variability of air-sea CO2 fluxes and the effect of net coral reef calcification in the Indonesian Seas: a numerical sensitivity study’


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Ocean acidification in the IPCC AR5 WG II

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