Helen E. Phillips

University of Tasmania

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Nathaniel L. Bindoff

Australian Antarctic Division

Ming Feng

CSIRO Oceans and Atmosphere

Ajitha Cyriac

University of Tasmania

Peter G. Strutton

University of Tasmania

Viviane V. Menezes

Woods Hole Oceanographic Institution

Ryo Furue

Japan Agency for Marine-Earth Science and Technology

Ramkrushnbhai Patel

University of Tasmania

Amélie Meyer

University of Tasmania

Stephen R. Rintoul

Commonwealth Scientific and Industrial Research Organisation

Bernadette M. Sloyan

CSIRO Oceans and Atmosphere

Cooperative Institutions

University of Tasmania

Australian Antarctic Division

Antarctic Climate and Ecosystems Cooperative Research Centre

ARC Centre of Excellence for Climate System Science

CSIRO Oceans and Atmosphere

Woods Hole Oceanographic Institution

UNSW Sydney

Commonwealth Scientific and Industrial Research Organisation

Australian Research Council

Centre National de la Recherche Scientifique

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Aquarius sea surface salinity in the South Indian Ocean: Revealing annual‐period planetary waves

Journal of Geophysical Research Oceans (2014)

Viviane V. Menezes Márcio L. Vianna Helen E. Phillips

Abstract A new milestone has been reached with the launch of two dedicated satellite missions to routinely measure the sea surface salinity (SSS) fields from space at global and regional scales. In the present work, a thorough analysis of the first 2 years of Aquarius SSS data in the South Indian Ocean is performed. This analysis is focused on three questions: How accurate is Aquarius SSS related to in situ data from the fresh Indonesian Throughflow and salty subtropical waters? Can Aquarius give a spatial context for the data measured by the RAMA mooring system? Are westward propagating annual‐period signals described in recent model simulations reproduced by Aquarius‐derived SSS? We find Aquarius observations to be highly correlated with those of Argo floats, with small disagreements occurring near oceanic fronts. Aquarius gives fresher SSS than in situ data in the tropical region due to rainfall effects, except in the eastern basin where the freshening seems to be related to sharp localized leakages of very fresh waters from the Indonesian seas that the Aquarius product is not able to properly resolve. Aquarius data are shown to reproduce quite well the annual cycle obtained from RAMA and Argo gridded data sets. The annual cycle in Aquarius is characterized by SSS propagating features with different characteristics west and east of the Ninety East Ridge. These features are strikingly different from sea surface height waves. Our results suggest that SSS annual propagation might be reflecting coupled ocean‐atmosphere dynamics and surface‐subsurface processes operating over the entire South Indian Ocean.

Argo

Bathythermograph

SSS*

10.1002/2014jc009935

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Mean Upper-Ocean Circulation of the Southern Hemisphere Oceans Based on Goce Data

AGUFM (2012)

Viviane V. Menezes Rory Bingham Márcio L. Vianna Helen E. Phillips

Circulation (fluid dynamics)

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Recent hemispheric asymmetry in global ocean warming induced by climate change and internal variability

Nature Communications (2020)

Saurabh Rathore Nathaniel L. Bindoff Helen E. Phillips Ming Feng

Recent research shows that 90% of the net global ocean heat gain during 2005-2015 was confined to the southern hemisphere with little corresponding heat gain in the northern hemisphere ocean. We propose that this heating pattern of the ocean is driven by anthropogenic climate change and an asymmetric climate variation between the two hemispheres. This asymmetric variation is found in the pre-industrial control simulations from 11 climate models. While both layers (0-700 m and 700-2000 m) experience steady anthropogenic warming, the 0-700 m layer experiences large internal variability, which primarily drives the observed hemispheric asymmetry of global ocean heat gain in 0-2000 m layer. We infer that the rate of global ocean warming is consistent with the climate simulations for this period. However, the observed hemispheric asymmetry in heat gain can be explained by the Earth's internal climate variability without invoking alternate hypotheses, such as asymmetric aerosol loading.

10.1038/s41467-020-15754-3

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Closing the loops on Southern Ocean dynamics: From the circumpolar current to ice shelves and from bottom mixing to surface waves

Authorea (Authorea) (2023)

Luke G. Bennetts Callum J. Shakespeare Catherine A. Vreugdenhil Annie Foppert Bishakhdatta Gayen

A holistic review is given of the Southern Ocean dynamic system, in the context of the crucial role it plays in the global climate and the profound changes it is experiencing. The review focuses on connections between different components of the Southern Ocean dynamic system, drawing together contemporary perspectives from different research communities, with the objective of 'closing loops' in our understanding of the complex network of feedbacks in the overall system. For the purposes of this review, the Southern Ocean dynamic system is divided into four main components: large-scale circulation; cryosphere; turbulence; and gravity waves. Overviews are given of the key dynamical phenomena for each component, before describing the linkages between the components. The reviews are complemented by an overview of observed Southern Ocean trends and future climate projections. Priority research areas required to improve our understanding of the Southern Ocean system are identified.

Circumpolar star

Earth system science

10.22541/essoar.168882017.73914213/v1

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High Resolution Current Velocity Profiling Floats Preliminary Results from Subantarctic Waters

Amélie Meyer Helen E. Phillips Bernadette M. Sloyan Nathaniel L. Bindoff

The Southern Ocean plays a crucial role in controlling the global climate system. To understand and predict climate variability, it is essential to know the mechanisms and the pathways of circulation in the global ocean. The EM-APEX (ElectroMagnetic-Autonomous Profiling EXplorer) is a recent addition to the Argo float fleet, capable of making very precise measurements of ocean velocities over a wide spatial and temporal range. Here we present some of the EM-APEX float capabilities and preliminary data from the Kerguelen Plateau region in the Southern Ocean.

Argo

Ocean observations

Profiling (computer programming)

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Eddy Variability and Energetics from Direct Current Measurements in the Antarctic Circumpolar Current South of Australia

Journal of Physical Oceanography (2000)

Helen E. Phillips Stephen R. Rintoul

Two-year time series measurements of current velocity and temperature in the Subantarctic Front (SAF) south of Australia from 1993 to 1995 provide estimates of eddy fluxes of heat and momentum across the Antarctic Circumpolar Current (ACC) and further insight into the variability of the ACC. The SAF was found to be an energetic, meandering jet with vertically coherent fluctuations varying on a timescale of 20 days with typical amplitude 30 cm s−1 at 1150 dbar. A daily varying coordinate frame that follows the direction of flow allowed mesoscale variability of the SAF to be isolated from variability due to meandering of the front and proved very successful for examining eddy fluxes. Vertically averaged cross-stream eddy heat flux was 11.3 kW m−2 poleward and significantly different from zero at 95% for fluctuations in the 2–90 day band. Zonally integrated, this eddy heat flux (=0.9 PW) is more than large enough to balance heat lost south of the Polar Front and is as large as cross-SAF fluxes found in Drake Passage. Cross-stream eddy momentum fluxes were small, not significantly different from zero, and of indeterminate sign, but tending to decelerate the mean flow. A relationship between vertical motion and meander phase identified in the Gulf Stream was found to hold for the ACC. Eddy kinetic energy levels were similar to those in Drake Passage and southeast of New Zealand. Eddy potential energy was up to an order of magnitude larger than at other ACC sites, most likely because meandering of the front is more common here. Baroclinic conversion was found to be the dominant mechanism by which eddies grow south of Australia. Typical eddy growth time is estimated to be 30 days, approximately twice as fast as in Drake Passage, consistent with eddy energy growing rapidly downstream.

Meander (mathematics)

Energetics

Polar front

Eddy

Gulf Stream

Eddy diffusion

Momentum (technical analysis)

10.1175/1520-0485(2000)030<3050:evaefd>2.0.co;2

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Citations (162)

Corrigendum: Detecting Change in the Indonesian Seas

Frontiers in Marine Science (2019)

Janet Sprintall Arnold L. Gordon Susan Wijffels Ming Feng Shijian Hu

CORRECTION article Front. Mar. Sci., 06 September 2019Sec. Ocean Observation Volume 6 - 2019 | https://doi.org/10.3389/fmars.2019.00549

10.3389/fmars.2019.00549

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Anomalous Ekman Transport Near Kerguelen Island

CJ Roach Helen E. Phillips Nathaniel L. Bindoff Rintoul

In this study we use data from 8 velocity profiling floats to examine the wind driven response of the surface layer of the Southern Ocean north of the Kerguelen Plateau during 2008. Assuming a constant geostrophic velocity within the upper 200m of the ocean we have identified Ekman-like spirals in 249 profiles and in the mean profile. Considering constant geostrophic shear this figure increased to 455 Ekman spirals. Mean Ekman transport was found to be skewed towards the wind, lying at 45° rather than 90° to the left of the wind as expected from steady-state Ekman theory for the Southern Hemisphere. This downwind transport anomaly was found to display little sensitivity to the presence of geostrophic shear or transient wind forcing. We suggest that the anomaly results from the „compression‟ observed in the mean spiral, possibly associated with ocean density stratification.

Ekman transport

Ekman layer

Geostrophic current

Stratification (seeds)

Ocean dynamics

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On the Leeuwin Current System and its linkage to zonal flows in the South Indian Ocean as inferred from a gridded hydrography

Japan Geoscience Union (2017)

Ryo Furue Kévin Guerreiro Helen E. Phillips Julian P. McCreary Nathaniel L. Bindoff

AbstractThe Leeuwin Current System (LCS) along the coast of Western Australia consists of the poleward-flowing Leeuwin Current (LC), the equatorward-flowing Leeuwin Undercurrent (LUC), and neighboring flows in the south Indian Ocean (SIO). Using geostrophic currents obtained from a highly resolved (⅛°) hydrographic climatology [CSIRO Atlas of Regional Seas (CARS)], this study describes the spatial structure and annual variability of the LC, LUC, and SIO zonal currents, estimates their transports, and identifies linkages among them. In CARS, the LC is supplied partly by water from the tropics (an annual mean of 0.3 Sv; 1 Sv ≡ 106 m3 s−1) but mostly by shallow (200 m) eastward flows in the SIO (4.7 Sv), and it loses water by downwelling across the bottom of this layer (3.4 Sv). The downwelling is so strong that, despite the large SIO inflow, the horizontal transport of the LC does not much increase to the south (from 0.3 Sv at 22°S to 1.5 Sv at 34°S). This LC transport is significantly smaller than previous...

Downwelling

Bathythermograph

Antarctic Intermediate Water

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