Variability and mesoscale activity of the Southern Ocean fronts: Identification of a circumpolar coordinate system

2011 ◽  
Vol 39 (1-2) ◽  
pp. 79-96 ◽  
Author(s):  
C. Langlais ◽  
S. Rintoul ◽  
A. Schiller
Keyword(s):  
Southern Ocean ◽  
Coordinate System ◽  
Ocean Fronts

scholarly journals The Seasonal Cycle of Blocking and Associated Physical Mechanisms in the Australian Region and Relationship with Rainfall

2013 ◽  
Vol 141 (12) ◽  
pp. 4534-4553 ◽  
Author(s):  
M. J. Pook ◽  
J. S. Risbey ◽  
P. C. McIntosh ◽  
C. C. Ummenhofer ◽  
A. G. Marshall ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Seasonal Cycle ◽  
Seasonal Temperature ◽  
Ocean Fronts ◽  
Temperature Changes ◽  
Physical Mechanisms ◽  
Australian Region ◽  
Continental Antarctica ◽  
Positive Correlations ◽  
Blocking Index

Abstract The seasonal cycle of blocking in the Australian region is shown to be associated with major seasonal temperature changes over continental Antarctica (approximately 15°–35°C) and Australia (about 8°–17°C) and with minor changes over the surrounding oceans (below 5°C). These changes are superimposed on a favorable background state for blocking in the region resulting from a conjunction of physical influences. These include the geographical configuration and topography of the Australian and Antarctic continents and the positive west to east gradient of sea surface temperature in the Indo-Australian sector of the Southern Ocean. Blocking is represented by a blocking index (BI) developed by the Australian Bureau of Meteorology. The BI has a marked seasonal cycle that reflects seasonal changes in the strength of the westerly winds in the midtroposphere at selected latitudes. Significant correlations between the BI at Australian longitudes and rainfall have been demonstrated in southern and central Australia for the austral autumn, winter, and spring. Patchy positive correlations are evident in the south during summer but significant negative correlations are apparent in the central tropical north. By decomposing the rainfall into its contributions from identifiable synoptic types during the April–October growing season, it is shown that the high correlation between blocking and rainfall in southern Australia is explained by the component of rainfall associated with cutoff lows. These systems form the cyclonic components of blocking dipoles. In contrast, there is no significant correlation between the BI and rainfall from Southern Ocean fronts.

scholarly journals Storms drive outgassing of CO2 in the subpolar Southern Ocean

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Sarah-Anne Nicholson ◽  
Daniel B. Whitt ◽  
Ilker Fer ◽  
Marcel D. du Plessis ◽  
Alice D. Lebéhot ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Critical Region ◽  
Process Model ◽  
Ekman Transport ◽  
Ocean Turbulence ◽  
Ocean Fronts ◽  
Ocean Variability ◽  
Synoptic Variability ◽  
Ocean Physics ◽  
Global Mean

AbstractThe subpolar Southern Ocean is a critical region where CO2 outgassing influences the global mean air-sea CO2 flux (FCO2). However, the processes controlling the outgassing remain elusive. We show, using a multi-glider dataset combining FCO2 and ocean turbulence, that the air-sea gradient of CO2 (∆pCO2) is modulated by synoptic storm-driven ocean variability (20 µatm, 1–10 days) through two processes. Ekman transport explains 60% of the variability, and entrainment drives strong episodic CO2 outgassing events of 2–4 mol m−2 yr−1. Extrapolation across the subpolar Southern Ocean using a process model shows how ocean fronts spatially modulate synoptic variability in ∆pCO2 (6 µatm2 average) and how spatial variations in stratification influence synoptic entrainment of deeper carbon into the mixed layer (3.5 mol m−2 yr−1 average). These results not only constrain aliased-driven uncertainties in FCO2 but also the effects of synoptic variability on slower seasonal or longer ocean physics-carbon dynamics.

scholarly journals Defining Southern Ocean fronts and their influence on biological and physical processes in a changing climate

2020 ◽  
Vol 10 (3) ◽  
pp. 209-219 ◽  
Author(s):  
Christopher C. Chapman ◽  
Mary-Anne Lea ◽  
Amelie Meyer ◽  
Jean-Baptiste Sallée ◽  
Mark Hindell
Keyword(s):  
Southern Ocean ◽  
Physical Processes ◽  
Ocean Fronts ◽  
Changing Climate

Variability of the Southern Ocean fronts at the Greenwich Meridian

2010 ◽  
Vol 82 (4) ◽  
pp. 304-310 ◽  
Author(s):  
W. Billany ◽  
S. Swart ◽  
J. Hermes ◽  
C.J.C. Reason
Keyword(s):  
Southern Ocean ◽  
Ocean Fronts ◽  
Greenwich Meridian

Structure of Southern Ocean fronts at 140°E

2002 ◽  
Vol 37 (1-3) ◽  
pp. 151-184 ◽  
Author(s):  
Serguei Sokolov ◽  
Stephen R Rintoul
Keyword(s):  
Southern Ocean ◽  
Ocean Fronts

Southern Ocean fronts from the Greenwich meridian to Tasmania

1996 ◽  
Vol 101 (C2) ◽  
pp. 3675-3696 ◽  
Author(s):  
Igor M. Belkin ◽  
Arnold L. Gordon
Keyword(s):  
Southern Ocean ◽  
Ocean Fronts ◽  
Greenwich Meridian

scholarly journals Southern Ocean fronts: Controlled by wind or topography?

2012 ◽  
Vol 117 (C8) ◽  
pp. n/a-n/a ◽  
Author(s):  
Robert M. Graham ◽  
Agatha M. de Boer ◽  
Karen J. Heywood ◽  
Mark R. Chapman ◽  
David P. Stevens
Keyword(s):  
Southern Ocean ◽  
Ocean Fronts

scholarly journals Defining Southern Ocean fronts using unsupervised classification

Ocean Science ◽  
2021 ◽  
Vol 17 (6) ◽  
pp. 1545-1562
Author(s):  
Simon D. A. Thomas ◽  
Daniel C. Jones ◽  
Anita Faul ◽  
Erik Mackie ◽  
Etienne Pauthenet
Keyword(s):  
Southern Ocean ◽  
Edge Detection ◽  
Detection Method ◽  
Unsupervised Classification ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Near Surface ◽  
Ocean Fronts ◽  
Dynamic Height ◽  
Edge Detection Method

Abstract. Oceanographic fronts are transitions between thermohaline structures with different characteristics. Such transitions are ubiquitous, and their locations and properties affect how the ocean operates as part of the global climate system. In the Southern Ocean, fronts have classically been defined using a small number of continuous, circumpolar features in sea surface height or dynamic height. Modern observational and theoretical developments are challenging and expanding this traditional framework to accommodate a more complex view of fronts. Here, we present a complementary new approach for calculating fronts using an unsupervised classification method called Gaussian mixture modelling (GMM) and a novel inter-class parameter called the I-metric. The I-metric approach produces a probabilistic view of front location, emphasising the fact that the boundaries between water masses are not uniformly sharp across the entire Southern Ocean. The I-metric approach uses thermohaline information from a range of depth levels, making it more general than approaches that only use near-surface properties. We train the GMM using an observationally constrained state estimate in order to have more uniform spatial and temporal data coverage. The probabilistic boundaries defined by the I-metric roughly coincide with several classically defined fronts, offering a novel view of this structure. The I-metric fronts appear to be relatively sharp in the open ocean and somewhat diffuse near large topographic features, possibly highlighting the importance of topographically induced mixing. For comparison with a more localised method, we also use an edge detection approach for identifying fronts. We find a strong correlation between the edge field of the leading principal component and the zonal velocity; the edge detection method highlights the presence of jets, which are supported by thermal wind balance. This more localised method highlights the complex, multiscale structure of Southern Ocean fronts, complementing and contrasting with the more domain-wide view offered by the I-metric. The Sobel edge detection method may be useful for defining and tracking smaller-scale fronts and jets in model or reanalysis data. The I-metric approach may prove to be a useful method for inter-model comparison, as it uses the thermohaline structure of those models instead of tracking somewhat ad hoc values of sea surface height and/or dynamic height, which can vary considerably between models. In addition, the general I-metric approach allows front definitions to shift with changing temperature and salinity structures, which may be useful for characterising fronts in a changing climate.

scholarly journals Abrupt transitions in dynamics of a NPZD model across Southern Ocean fronts

2017 ◽  
Vol 359 ◽  
pp. 372-382 ◽  
Author(s):  
C. Robert Priester ◽  
Jessica Melbourne-Thomas ◽  
Andreas Klocker ◽  
Stuart Corney
Keyword(s):  
Southern Ocean ◽  
Ocean Fronts

Identifying Southern Ocean fronts using unsupervised classification and edge detection

2021 ◽  
Author(s):  
Simon Thomas ◽  
Dan Jones ◽  
Anita Faul ◽  
Erik Mackie ◽  
Etienne Pauthenet
Keyword(s):  
Southern Ocean ◽  
Edge Detection ◽  
Unsupervised Classification ◽  
Ocean Fronts
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