La Niña forces unprecedented Leeuwin Current warming in 2011

Area of Science:

• Marine heatwaves
• Oceanography
• Climate science

Background:

• Unprecedented sea surface temperature (SST) anomalies occurred off Western Australia in Feb-Mar 2011.
• Peak SST reached 5°C above normal, causing significant coral bleaching and fish kills.
• This extreme event, termed "Ningaloo Niño", necessitates understanding its climatic drivers for future predictions.

Purpose of the Study:

• To identify the climatic drivers of the 2011 Ningaloo Niño marine heatwave.
• To assess the role of the Leeuwin Current in the extreme warming event.
• To understand the influence of global warming on such phenomena.

Main Methods:

• Analysis of observational data.
• Utilisation of numerical oceanographic models.
• Investigation of oceanic and atmospheric teleconnections.

Main Results:

• The extreme warming was primarily caused by an intensified, poleward-flowing Leeuwin Current.
• Anomalously warm water was transported southward along the coast by the current.
• The Leeuwin Current's surge was linked to the 2010-2011 La Niña event.

Conclusions:

• The Ningaloo Niño was driven by remote forcing from La Niña via teleconnections.
• Multi-decadal Pacific trends and Indian Ocean variations amplified the warming.
• Understanding these drivers is critical for predicting future marine heatwaves under climate change.