Study of seasonal variability and heat budget of the East Australian Current using two eddy-resolving ocean circulation models

Wang, Xiaohua; Bhatt, Vihang; Sun, Youn-Jong

doi:10.1007/s10236-013-0605-5

Cited by 12 publications

(13 citation statements)

References 46 publications

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“…A suggestion of seasonality is shown in the boxplots for the VARY‐LOCAL and VARY‐ALL experiments at FE and AB (Figures g and i). At FE, this is likely the documented summertime peak in upstream EAC transport (Ridgway & Godfrey, ; Wang et al, ). It is notable that remote forcing appears to play little role in the seasonality of the upstream EAC (VARY‐OBC, Figure a).…”

Section: Resultsmentioning

confidence: 89%

Wind Forced Variability in Eddy Formation, Eddy Shedding, and the Separation of the East Australian Current

et al. 2017

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The East Australian Current (EAC), like many other subtropical western boundary currents, is believed to be penetrating further poleward in recent decades. Previous observational and model studies have used steady state dynamics to relate changes in the westerly winds to changes in the separation behavior of the EAC. As yet, little work has been undertaken on the impact of forcing variability on the EAC and Tasman Sea circulation. Here using an eddy‐permitting regional ocean model, we present a suite of simulations forced by the same time‐mean fields, but with different atmospheric and remote ocean variability. These eddy‐permitting results demonstrate the nonlinear response of the EAC to variable, nonstationary inhomogeneous forcing. These simulations show an EAC with high intrinsic variability and stochastic eddy shedding. We show that wind stress variability on time scales shorter than 56 days leads to increases in eddy shedding rates and southward eddy propagation, producing an increased transport and southward reach of the mean EAC extension. We adopt an energetics framework that shows the EAC extension changes to be coincident with an increase in offshore, upstream eddy variance (via increased barotropic instability) and increase in subsurface mean kinetic energy along the length of the EAC. The response of EAC separation to regional variable wind stress has important implications for both past and future climate change studies.

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Section: Resultsmentioning

confidence: 89%

Wind Forced Variability in Eddy Formation, Eddy Shedding, and the Separation of the East Australian Current

et al. 2017

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“…[] showed that OFES is in good agreement with observations around Australia. More recently, a study on heat budget along the EAC found that annual mean transports at 28°S obtained from OFES agree with those computed from observations [ Wang et al ., ]. OFES outputs are therefore ideal to investigate circulation along the coast of southeastern Australia.…”

Section: Methodsmentioning

confidence: 99%

Long‐term trends in the East Australian Current separation latitude and eddy driven transport

et al. 2014

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An observed warming of the Tasman Sea in recent decades has been linked to a poleward shift of the maximum wind stress curl, and a strengthening of the poleward flow along the coast of southeastern Australia. However, changes in the East Australian Current (EAC) separation latitude, as well as in the contribution of the EAC, the EAC extension and its eddy field to the total southward transport due to such a strengthening remain unknown. This study uses 30 years of the Ocean Forecast for the Earth Simulator (OFES) sea surface height and velocity outputs to obtain a three decade long-time series of (i) the EAC separation latitude, (ii) the southward transport along the coast of southeastern Australia (28 S-39 S), and (iii) the southward transport across the EAC separation latitude. A Lagrangian approach is implemented and the spin parameter X is used to provide a quantitative distinction between the transports occurring outside and inside (cyclonic and anticyclonic) eddies. Significant positive trends of the low pass southward transports indicate that the intensification of the poleward flow has occurred both within the EAC and in the EAC extension. In addition, a significant increase in southward transport inside and outside eddies is found. Importantly, the contribution of eddy driven transport has a large temporal variability and shows a sharp increase from 2005 onward. Finally our results show that the EAC has not penetrated further south but it has separated more frequently at the southernmost latitudes within the region where it typically turns eastward.

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“…Prior to separation, the upstream EAC has a range of observed and modeled transports from past studies; observed estimates include 27.4 Sv (Ridgway & Godfrey, 1994) and 25.8 Sv (derived from CARS; Ridgway et al, 2002). Modeling estimates of EAC transport range between 20.4 and 30 Sv (Oliver & Holbrook, 2014;Wang et al, 2013;Ypma et al, 2016). In our study, the modeled CTRL upstream EAC transport to 1,945 m across 1548E-1568E at 288S is 24.3 Sv (Figure 3), and therefore within both modeled and observed estimates of EAC transport, and also consistent with the 22.1 6 7.5 Sv directly observed transport at 278S (Sloyan et al 2016).…”

Section: Experimental Designmentioning

confidence: 99%

The Role of the New Zealand Plateau in the Tasman Sea Circulation and Separation of the East Australian Current

et al. 2018

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The East Australian Current (EAC) plays a major role in regional climate, circulation, and ecosystems, but predicting future changes is hampered by limited understanding of the factors controlling EAC separation. While there has been speculation that the presence of New Zealand may be important for the EAC separation, the prevailing view is that the time‐mean partial separation is set by the ocean's response to gradients in the wind stress curl. This study focuses on the role of New Zealand, and the associated adjacent bathymetry, in the partial separation of the EAC and ocean circulation in the Tasman Sea. Here utilizing an eddy‐permitting ocean model (NEMO), we find that the complete removal of the New Zealand plateau leads to a smaller fraction of EAC transport heading east and more heading south, with the mean separation latitude shifting >100 km southward. To examine the underlying dynamics, we remove New Zealand with two linear models: the Sverdrup/Godfrey Island Rule and NEMO in linear mode. We find that linear processes and deep bathymetry play a major role in the mean Tasman Front position, whereas nonlinear processes are crucial for the extent of the EAC retroflection. Contrary to past work, we find that meridional gradients in the basin‐wide wind stress curl are not the sole factor determining the latitude of EAC separation. We suggest that the Tasman Front location is set by either the maximum meridional gradient in the wind stress curl or the northern tip of New Zealand, whichever is furthest north.

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Study of seasonal variability and heat budget of the East Australian Current using two eddy-resolving ocean circulation models

Cited by 12 publications

References 46 publications

Wind Forced Variability in Eddy Formation, Eddy Shedding, and the Separation of the East Australian Current

Wind Forced Variability in Eddy Formation, Eddy Shedding, and the Separation of the East Australian Current

Long‐term trends in the East Australian Current separation latitude and eddy driven transport

The Role of the New Zealand Plateau in the Tasman Sea Circulation and Separation of the East Australian Current

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