Dynamics of Transport, Accumulation, and Export of Plastics at Oceanic Fronts

2021 ◽  
Author(s):  
G. Suaria ◽  
M. Berta ◽  
A. Griffa ◽  
A. Molcard ◽  
T. M. Özgökmen ◽  
...  
Keyword(s):  
Oceanic Fronts

scholarly journals Hydrographic shifts south of Australia over the last deglaciation and possible interhemispheric linkages

2021 ◽  
pp. 1-12
Author(s):  
Matthias Moros ◽  
Patrick De Deckker ◽  
Kerstin Perner ◽  
Ulysses S. Ninnemann ◽  
Lukas Wacker ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Southern Hemisphere ◽  
Critical Role ◽  
Temperature Response ◽  
South Australia ◽  
Last Deglaciation ◽  
Tight Coupling ◽  
Oceanic Fronts ◽  
The Last Deglaciation ◽  
Circumpolar Current

Abstract Northern and southern hemispheric influences—particularly changes in Southern Hemisphere westerly winds (SSW) and Southern Ocean ventilation—triggered the stepwise atmospheric CO2 increase that accompanied the last deglaciation. One approach for gaining potential insights into past changes in SWW/CO2 upwelling is to reconstruct the positions of the northern oceanic fronts associated with the Antarctic Circumpolar Current. Using two deep-sea cores located ~600 km apart off the southern coast of Australia, we detail oceanic changes from ~23 to 6 ka using foraminifer faunal and biomarker alkenone records. Our results indicate a tight coupling between hydrographic and related frontal displacements offshore South Australia (and by analogy, possibly the entire Southern Ocean) and Northern Hemisphere (NH) climate that may help confirm previous hypotheses that the westerlies play a critical role in modulating CO2 uptake and release from the Southern Ocean on millennial and potentially even centennial timescales. The intensity and extent of the northward displacements of the Subtropical Front following well-known NH cold events seem to decrease with progressing NH ice sheet deglaciation and parallel a weakening NH temperature response and amplitude of Intertropical Convergence Zone shifts. In addition, an exceptional poleward shift of Southern Hemisphere fronts occurs during the NH Heinrich Stadial 1. This event was likely facilitated by the NH ice maximum and acted as a coup-de-grâce for glacial ocean stratification and its high CO2 capacitance. Thus, through its influence on the global atmosphere and on ocean mixing, “excessive” NH glaciation could have triggered its own demise by facilitating the destratification of the glacial ocean CO2 state.

scholarly journals Change in the North Atlantic circulation associated with the mid-Pleistocene transition

2018 ◽  
Vol 14 (11) ◽  
pp. 1639-1651 ◽  
Author(s):  
Gloria M. Martin-Garcia ◽  
Francisco J. Sierro ◽  
José A. Flores ◽  
Fátima Abrantes
Keyword(s):  
North Atlantic ◽  
Major Change ◽  
Water Masses ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
North Atlantic Current ◽  
The North ◽  
Oceanic Fronts ◽  
Surface Circulation ◽  
The North Atlantic

Abstract. The southwestern Iberian margin is highly sensitive to changes in the distribution of North Atlantic currents and to the position of oceanic fronts. In this work, the evolution of oceanographic parameters from 812 to 530 ka (MIS20–MIS14) is studied based on the analysis of planktonic foraminifer assemblages from site IODP-U1385 (37∘34.285′ N, 10∘7.562′ W; 2585 m b.s.l.). By comparing the obtained results with published records from other North Atlantic sites between 41 and 55∘ N, basin-wide paleoceanographic conditions are reconstructed. Variations of assemblages dwelling in different water masses indicate a major change in the general North Atlantic circulation during MIS16, coinciding with the definite establishment of the 100 ky cyclicity associated with the mid-Pleistocene transition. At the surface, this change consisted in the redistribution of water masses, with the subsequent thermal variation, and occurred linked to the northwestward migration of the Arctic Front (AF), and the increase in the North Atlantic Deep Water (NADW) formation with respect to previous glacials. During glacials prior to MIS16, the NADW formation was very weak, which drastically slowed down the surface circulation; the AF was at a southerly position and the North Atlantic Current (NAC) diverted southeastwards, developing steep south–north, and east–west, thermal gradients and blocking the arrival of warm water, with associated moisture, to high latitudes. During MIS16, the increase in the meridional overturning circulation, in combination with the northwestward AF shift, allowed the arrival of the NAC to subpolar latitudes, multiplying the moisture availability for ice-sheet growth, which could have worked as a positive feedback to prolong the glacials towards 100 ky cycles.

scholarly journals Storm Track Response to Oceanic Eddies in Idealized Atmospheric Simulations

2018 ◽  
Vol 32 (2) ◽  
pp. 445-463 ◽  
Author(s):  
A. Foussard ◽  
G. Lapeyre ◽  
R. Plougonven
Keyword(s):  
Large Scale ◽  
Heat Budget ◽  
Storm Track ◽  
Convective Heating ◽  
Western Boundary ◽  
Boundary Currents ◽  
Oceanic Fronts ◽  
Budget Analysis ◽  
Poleward Shift ◽  
Oceanic Eddies

ABSTRACT Large-scale oceanic fronts, such as in western boundary currents, have been shown to play an important role in the dynamics of atmospheric storm tracks. Little is known about the influence of mesoscale oceanic eddies on the free troposphere, although their imprint on the atmospheric boundary layer is well documented. The present study investigates the response of the tropospheric storm track to the presence of sea surface temperature (SST) anomalies associated with an eddying ocean. Idealized experiments are carried out in a configuration of a zonally reentrant channel representing the midlatitudes. The SST field is composed of a large-scale zonally symmetric front to which are added mesoscale eddies localized close to the front. Numerical simulations show a robust signal of a poleward shift of the storm track and of the tropospheric eddy-driven jet when oceanic eddies are taken into account. This is accompanied by more intense air–sea fluxes and convective heating above oceanic eddies. Also, a mean heating of the troposphere occurs poleward of the oceanic eddying region, within the storm track. A heat budget analysis shows that it is caused by a stronger diabatic heating within storms associated with more water advected poleward. This additional heating affects the baroclinicity of the flow, which pushes the jet and the storm track poleward.

scholarly journals Detection of Fronts as a Metric for Numerical Model Accuracy

2019 ◽  
Vol 36 (8) ◽  
pp. 1547-1561
Author(s):  
Elizabeth M. Douglass ◽  
Andrea C. Mask
Keyword(s):  
Numerical Model ◽  
Region Of Interest ◽  
Ocean Model ◽  
Minimum Size ◽  
Model Output ◽  
Oceanic Fronts ◽  
Hybrid Coordinate Ocean Model ◽  
Quantitative Metrics ◽  
Coastal Ocean Model ◽  
Along Track

AbstractAs numerical modeling advances, quantitative metrics are necessary to determine whether the model output accurately represents the observed ocean. Here, a metric is developed based on whether a model places oceanic fronts in the proper location. Fronts are observed and assessed directly from along-track satellite altimetry. Numerical model output is then interpolated to the locations of the along-track data, and fronts are detected in the model output. Scores are determined from the percentage of observed fronts correctly simulated in the model and from the percentage of modeled fronts confirmed by observations. These scores depend on certain parameters such as the minimum size of a front, which will be shown to be geographically dependent. An analysis of two models, the Hybrid Coordinate Ocean Model (HYCOM) and the Navy Coastal Ocean Model (NCOM), is presented as an example of how this metric might be applied and interpreted. In this example, scores are found to be relatively stable in time, but strongly dependent on the mesoscale variability in the region of interest. In all cases, the metric indicates that there are more observed fronts not found in the models than there are modeled fronts missing from observations. In addition to the score itself, the analysis demonstrates that modeled fronts have smaller amplitude and are less steep than observed fronts.

Observed Associations Among Storm Tracks, Jet Streams and Midlatitude Oceanic Fronts

2013 ◽  
pp. 329-345 ◽  
Author(s):  
Hisashi Nakamura ◽  
Takeaki Sampe ◽  
Youichi Tanimoto ◽  
Akihiko Shimpo
Keyword(s):  
Storm Tracks ◽  
Jet Streams ◽  
Oceanic Fronts

Oceanic fronts and jets around Japan: a review

2016 ◽  
pp. 1-30
Author(s):  
Shinichiro Kida ◽  
Humio Mitsudera ◽  
Shigeru Aoki ◽  
Xinyu Guo ◽  
Shin-ichi Ito ◽  
...  
Keyword(s):  
Oceanic Fronts

Coastally trapped waves, baroclinic eddies, internal tides and oceanic fronts at the shelf break: their implications for exchanges between shelf and oceanic waters

1981 ◽  
Vol 302 (1472) ◽  
pp. 661-661 ◽  
Keyword(s):  
Coastal Waters ◽  
Coastal Upwelling ◽  
Shelf Break ◽  
Internal Tides ◽  
Oceanic Fronts ◽  
Run Off ◽  
Break Surface ◽  
Seaward Edge ◽  
Coastally Trapped Waves ◽  
Topographic Rossby Waves

The seaward edge of the continental shelf, or shelf break, is the locus of strong physical variability in the overlying waters. Near the shelf-break, surface tides scatter energy into internal modes that propagate both onshore and offshore and produce strong vertical shears. Atmospheric forcing generates subinertial-frequency topographic Rossby waves, which propagate parallel to the coastline and are strongly trapped near the shelf break. Relative to the sloping topography, wind-driven coastal upwelling generates prograde fronts, and river run-off generates retrograde fronts. Located near the shelf break, these fronts are boundaries between oceanic and coastal waters. Oceanic eddies impinge on, and move along, the shelf-break entraining coastal waters. Eddies may also be shed by shelf-break fronts. Submarine capes and canyons contort the shelf break and significantly modify the enumerated processes. Based on observational evidence from a few coastal regimes, the shelf break is a zone where several mesoscale and synoptic-scale processes operate and probably produce significant turbulent transfers.

scholarly journals Coccolithophore biodiversity controls carbonate export in the Southern Ocean

2020 ◽  
Vol 17 (1) ◽  
pp. 245-263 ◽  
Author(s):  
Andrés S. Rigual Hernández ◽  
Thomas W. Trull ◽  
Scott D. Nodder ◽  
José A. Flores ◽  
Helen Bostock ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Deep Sea ◽  
Global Climate ◽  
Chemical Properties ◽  
Austral Summer ◽  
Major Fraction ◽  
Oceanic Fronts ◽  
Phytoplankton Communities ◽  
Physical And Chemical ◽  
Particulate Inorganic Carbon

Abstract. Southern Ocean waters are projected to undergo profound changes in their physical and chemical properties in the coming decades. Coccolithophore blooms in the Southern Ocean are thought to account for a major fraction of the global marine calcium carbonate (CaCO3) production and export to the deep sea. Therefore, changes in the composition and abundance of Southern Ocean coccolithophore populations are likely to alter the marine carbon cycle, with feedbacks to the rate of global climate change. However, the contribution of coccolithophores to CaCO3 export in the Southern Ocean is uncertain, particularly in the circumpolar subantarctic zone that represents about half of the areal extent of the Southern Ocean and where coccolithophores are most abundant. Here, we present measurements of annual CaCO3 flux and quantitatively partition them amongst coccolithophore species and heterotrophic calcifiers at two sites representative of a large portion of the subantarctic zone. We find that coccolithophores account for a major fraction of the annual CaCO3 export, with the highest contributions in waters with low algal biomass accumulations. Notably, our analysis reveals that although Emiliania huxleyi is an important vector for CaCO3 export to the deep sea, less abundant but larger species account for most of the annual coccolithophore CaCO3 flux. This observation contrasts with the generally accepted notion that high particulate inorganic carbon accumulations during the austral summer in the subantarctic Southern Ocean are mainly caused by E. huxleyi blooms. It appears likely that the climate-induced migration of oceanic fronts will initially result in the poleward expansion of large coccolithophore species increasing CaCO3 production. However, subantarctic coccolithophore populations will eventually diminish as acidification overwhelms those changes. Overall, our analysis emphasizes the need for species-centred studies to improve our ability to project future changes in phytoplankton communities and their influence on marine biogeochemical cycles.

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