Details

Autor(en) / Beteiligte

• Archer, Matthew R.
• Roughan, Moninya
• Keating, Shane R.
• Schaeffer, Amandine

Titel

On the Variability of the East Australian Current: Jet Structure, Meandering, and Influence on Shelf Circulation

Ist Teil von

• Journal of geophysical research. Oceans, 2017-11, Vol.122 (11), p.8464-8481

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2017

Link zum Volltext

Quelle

Wiley Online Library All Journals

Beschreibungen/Notizen

• Given the importance of western boundary currents over a wide range of scales in the ocean, it is crucial that we understand their dynamics to accurately predict future changes. For this, we need detailed knowledge of their structure and variability. Here we investigate the jet structure of the East Australian Current (EAC), using observations from HF radars and moorings deployed at 30°S–31°S. Meandering, core velocity, width, and eddy kinetic energy (EKE) are quantified from 4 years of hourly 1.5 km resolution surface current maps (2012–2016), to obtain the most detailed representation of the surface EAC jet to date. The EAC flows predominantly over the ∼1,500 m isobath 50 km offshore but makes large amplitude displacements eastward every 65–100 days—the time scale associated with mesoscale eddy shedding at the EAC separation. Smaller‐amplitude, higher‐frequency meanders occur every 20–45 days. Using a coordinate frame that follows the jet, we show core velocity and EKE exhibit seasonality in both magnitude and variance, being maximum in summer (1.55 m s−1 mean core velocity), minimum in winter (0.8 m s−1). However, it is the eddy‐shedding time scale that dominates jet variability. As the EAC moves shoreward, shelf temperature and along‐stream velocity vary linearly with jet movement, within ∼35 km of the core. The EAC is within this range 75% of the time, demonstrating its importance to the shelf circulation. Temperature and velocity fluctuations at the 70 m (100 m) isobath are more influenced by wind (EAC encroachment), with the strongest response occurring when wind and EAC act constructively. Key Points Meandering, core velocity, width, and eddy kinetic energy of the East Australian Current exhibit dominant variability at 65–100 days An annual cycle in the EAC core velocity and eddy kinetic energy has a maximum mean magnitude and variance in summer and minimum in winter Onshore movement of the EAC linearly increases shelf temperature and along‐stream velocity within a range of ∼35 km from its core