scholarly journals Multi-nutrient, multi-group model of present and future oceanic phytoplankton communities

2006 ◽  
Vol 3 (4) ◽  
pp. 585-606 ◽  
Author(s):  
E. Litchman ◽  
C. A. Klausmeier ◽  
J. R. Miller ◽  
O. M. Schofield ◽  
P. G. Falkowski
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Phytoplankton Community ◽  
Zooplankton Biomass ◽  
Nutrient Concentrations ◽  
Phytoplankton Community Structure ◽  
The North ◽  
Phytoplankton Communities ◽  
The North Atlantic ◽  
The North Pacific

Abstract. Phytoplankton community composition profoundly affects patterns of nutrient cycling and the dynamics of marine food webs; therefore predicting present and future phytoplankton community structure is crucial to understand how ocean ecosystems respond to physical forcing and nutrient limitations. We develop a mechanistic model of phytoplankton communities that includes multiple taxonomic groups (diatoms, coccolithophores and prasinophytes), nutrients (nitrate, ammonium, phosphate, silicate and iron), light, and a generalist zooplankton grazer. Each taxonomic group was parameterized based on an extensive literature survey. We test the model at two contrasting sites in the modern ocean, the North Atlantic (North Atlantic Bloom Experiment, NABE) and subarctic North Pacific (ocean station Papa, OSP). The model successfully predicts general patterns of community composition and succession at both sites: In the North Atlantic, the model predicts a spring diatom bloom, followed by coccolithophore and prasinophyte blooms later in the season. In the North Pacific, the model reproduces the low chlorophyll community dominated by prasinophytes and coccolithophores, with low total biomass variability and high nutrient concentrations throughout the year. Sensitivity analysis revealed that the identity of the most sensitive parameters and the range of acceptable parameters differed between the two sites. We then use the model to predict community reorganization under different global change scenarios: a later onset and extended duration of stratification, with shallower mixed layer depths due to increased greenhouse gas concentrations; increase in deep water nitrogen; decrease in deep water phosphorus and increase or decrease in iron concentration. To estimate uncertainty in our predictions, we used a Monte Carlo sampling of the parameter space where future scenarios were run using parameter combinations that produced acceptable modern day outcomes and the robustness of the predictions was determined. Change in the onset and duration of stratification altered the timing and the magnitude of the spring diatom bloom in the North Atlantic and increased total phytoplankton and zooplankton biomass in the North Pacific. Changes in nutrient concentrations in some cases changed dominance patterns of major groups, as well as total chlorophyll and zooplankton biomass. Based on these scenarios, our model suggests that global environmental change will inevitably alter phytoplankton community structure and potentially impact global biogeochemical cycles.

scholarly journals Multi-nutrient, multi-group model of present and future oceanic phytoplankton communities

2006 ◽  
Vol 3 (3) ◽  
pp. 607-663 ◽  
Author(s):  
E. Litchman ◽  
C. A. Klausmeier ◽  
J. R. Miller ◽  
O. M. Schofield ◽  
P. G. Falkowski
Keyword(s):  
Community Structure ◽  
North Atlantic ◽  
North Pacific ◽  
Phytoplankton Community ◽  
Total Chlorophyll ◽  
Diatom Bloom ◽  
The North ◽  
Phytoplankton Communities ◽  
The North Atlantic ◽  
The North Pacific

Abstract. Phytoplankton community composition profoundly influences patterns of nutrient cycling and the structure of marine food webs; therefore predicting present and future phytoplankton community structure is of fundamental importance to understanding how ocean ecosystems are influenced by physical forcing and nutrient limitations. In this paper, we develop a mechanistic model of phytoplankton communities that includes multiple taxonomic groups, test the model at two contrasting sites in the modern ocean, and then use the model to predict community reorganization under different global change scenarios. The model includes three phytoplankton functional groups (diatoms, coccolithophores, and prasinophytes), five nutrients (nitrate, ammonium, phosphate, silicate and iron), light, and a generalist zooplankton grazer. Each taxonomic group was parameterized based on an extensive literature survey. The model successfully predicts the general patterns of community structure and succession in contrasting parts of the world ocean, the North Atlantic (North Atlantic Bloom Experiment, NABE) and subarctic North Pacific (ocean station Papa, OSP). In the North Atlantic, the model predicts a spring diatom bloom, followed by coccolithophore and prasinophyte blooms later in the season. The diatom bloom becomes silica-limited and the coccolithophore and prasinophyte blooms are controlled by nitrogen, grazers and by deep mixing and decreasing light availability later in the season. In the North Pacific, the model reproduces the low chlorophyll community dominated by prasinophytes and coccolithophores, with low total biomass variability and high nutrient concentrations throughout the year. Sensitivity analysis revealed that the identity of the most sensitive parameters and the range of acceptable parameters differed between the two sites. Five global change scenarios are used to drive the model and examine how community dynamics might change in the future. To estimate uncertainty in our predictions, we used a Monte Carlo sampling of the parameter space where future scenarios were run using parameter combinations that produced adequate modern day outcomes. The first scenario is based on a global climate model that indicates that increased greenhouse gas concentrations will cause a later onset and extended duration of stratification and shallower mixed layer depths. Under this scenario, the North Atlantic spring diatom bloom occurs later and is of a smaller magnitude, but the average biomass of diatoms, coccolithophores and prasinophytes will likely increase. In the subarctic North Pacific, diatoms and prasinophytes will likely increase along with total chlorophyll concentration and zooplankton. In contrast, coccolithophore densities do not change at this site. Under the second scenario of decreased deep-water phosphorus concentration, coccolithophores, total chlorophyll and zooplankton decline, as well as the magnitude of the spring diatom bloom, while the average diatom and prasinophyte abundance does not change in the North Atlantic. In contrast, a decrease in phosphorus in the North Pacific is not likely to change community composition. Similarly, doubling of nitrate in deep water does not significantly affect ecosystems at either site. Under decreased iron deposition, coccolithophores are likely to increase and other phytoplankton groups and zooplankton to decrease at both sites. An increase in iron deposition is likely to increase prasinophyte and diatom abundance and decrease coccolithophore abundance at both sites, although more dramatically at the North Pacific site. Total chlorophyll and zooplankton are also likely to increase under this scenario at both sites. Based on these scenarios, our model suggests that global environmental change will inevitably alter phytoplankton community structure and potentially impact global biogeochemical cycles.

The Role of Oscillating Southern Hemisphere Westerly Winds: Global Ocean Circulation

2020 ◽  
Vol 33 (6) ◽  
pp. 2111-2130
Author(s):  
Woo Geun Cheon ◽  
Jong-Seong Kug
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
North Pacific ◽  
Global Ocean ◽  
The North ◽  
Westerly Winds ◽  
The North Atlantic ◽  
Global Ocean Circulation ◽  
The Antarctic ◽  
The North Pacific

AbstractIn the framework of a sea ice–ocean general circulation model coupled to an energy balance atmospheric model, an intensity oscillation of Southern Hemisphere (SH) westerly winds affects the global ocean circulation via not only the buoyancy-driven teleconnection (BDT) mode but also the Ekman-driven teleconnection (EDT) mode. The BDT mode is activated by the SH air–sea ice–ocean interactions such as polynyas and oceanic convection. The ensuing variation in the Antarctic meridional overturning circulation (MOC) that is indicative of the Antarctic Bottom Water (AABW) formation exerts a significant influence on the abyssal circulation of the globe, particularly the Pacific. This controls the bipolar seesaw balance between deep and bottom waters at the equator. The EDT mode controlled by northward Ekman transport under the oscillating SH westerly winds generates a signal that propagates northward along the upper ocean and passes through the equator. The variation in the western boundary current (WBC) is much stronger in the North Atlantic than in the North Pacific, which appears to be associated with the relatively strong and persistent Mindanao Current (i.e., the southward flowing WBC of the North Pacific tropical gyre). The North Atlantic Deep Water (NADW) formation is controlled by salt advected northward by the North Atlantic WBC.

Satellite-Derived Tropical Cyclone Intensity in the North Pacific Ocean Using the Deviation-Angle Variance Technique

2014 ◽  
Vol 29 (3) ◽  
pp. 505-516 ◽  
Author(s):  
Elizabeth A. Ritchie ◽  
Kimberly M. Wood ◽  
Oscar G. Rodríguez-Herrera ◽  
Miguel F. Piñeros ◽  
J. Scott Tyo
Keyword(s):  
Tropical Cyclone ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Deviation Angle ◽  
Intensity Estimation ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract The deviation-angle variance technique (DAV-T), which was introduced in the North Atlantic basin for tropical cyclone (TC) intensity estimation, is adapted for use in the North Pacific Ocean using the “best-track center” application of the DAV. The adaptations include changes in preprocessing for different data sources [Geostationary Operational Environmental Satellite-East (GOES-E) in the Atlantic, stitched GOES-E–Geostationary Operational Environmental Satellite-West (GOES-W) in the eastern North Pacific, and the Multifunctional Transport Satellite (MTSAT) in the western North Pacific], and retraining the algorithm parameters for different basins. Over the 2007–11 period, DAV-T intensity estimation in the western North Pacific results in a root-mean-square intensity error (RMSE, as measured by the maximum sustained surface winds) of 14.3 kt (1 kt ≈ 0.51 m s−1) when compared to the Joint Typhoon Warning Center best track, utilizing all TCs to train and test the algorithm. The RMSE obtained when testing on an individual year and training with the remaining set lies between 12.9 and 15.1 kt. In the eastern North Pacific the DAV-T produces an RMSE of 13.4 kt utilizing all TCs in 2005–11 when compared with the National Hurricane Center best track. The RMSE for individual years lies between 9.4 and 16.9 kt. The complex environment in the western North Pacific led to an extension to the DAV-T that includes two different radii of computation, producing a parametric surface that relates TC axisymmetry to intensity. The overall RMSE is reduced by an average of 1.3 kt in the western North Pacific and 0.8 kt in the eastern North Pacific. These results for the North Pacific are comparable with previously reported results using the DAV for the North Atlantic basin.

scholarly journals Dynamical and biogeochemical control on the decadal variability of ocean carbon fluxes

2012 ◽  
Vol 3 (2) ◽  
pp. 1347-1389
Author(s):  
R. Séférian ◽  
L. Bopp ◽  
D. Swingedouw ◽  
J. Servonnat
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Carbon Flux ◽  
Carbon Fluxes ◽  
Modes Of Variability ◽  
The North ◽  
The North Atlantic ◽  
Ocean Carbon ◽  
The North Pacific ◽  
Regional Variance

Abstract. Several recent observation-based studies suggest that ocean anthropogenic carbon uptake has slowed down due to the impact of anthropogenic forced climate change. However, it remains unclear if detected changes over the recent time period can really be attributed to anthropogenic climate change or to natural climate variability (internal plus naturally forced variability). One large uncertainty arises from the lack of knowledge on ocean carbon flux natural variability at the decadal time scales. To gain more insights into decadal time scales, we have examined the internal variability of ocean carbon fluxes in a 1000-yr long preindustrial simulation performed with the Earth System Model IPSL-CM5A-LR. Our analysis shows that ocean carbon fluxes exhibit low-frequency oscillations that emerge from their year-to-year variability in the North Atlantic, the North Pacific, and the Southern Ocean. In our model, a 20-yr mode of variability in the North Atlantic air-sea carbon flux is driven by sea surface temperature variability and accounts for ~40% of the interannual regional variance. The North Pacific and the Southern Ocean carbon fluxes are also characterized by decadal to multi-decadal modes of variability (10 to 50 yr) that account for 30–40% of the interannual regional variance. But these modes are driven by the vertical supply of dissolved inorganic carbon through the variability of Ekman-induced upwelling and deep-mixing events. Differences in drivers of regional modes of variability stem from the coupling between ocean dynamics variability and the ocean carbon distribution, which is set by large-scale secular ocean circulation.

Sign in / Sign up

Export Citation Format

Share Document