The Leeuwin Current is running a fever, with sea surface temperatures off the Western Australian coast currently significantly higher than normal.

It’s been sitting over marine heatwave thresholds for weeks, likely impacting the state's marine ecosystems.

Satellite observations of the sea surface temperature anomalies - which measure the difference above or below the long-term average - across the Indian Ocean basin reveal the warmer-than-normal sea surface temperature signature off Western Australia, hugging the coast from Port Hedland all the way down to Margaret River.

Sea surface temperature anomalies for the Indian Ocean as of 9th February (NOAA)

Anomalies are mostly sitting at 2-3°C above normal but there are vast areas pushing over 4°C above normal.

What’s also visible is a cooling signature south of Indonesia and this is thanks to dual tropical cyclones moving slowly through the region. Those being Severe Tropical Cyclone Vince and Tropical Cyclone Taliah.

The drivers behind the recent warming are a double whammy of stronger-than-normal easterly trade-winds in the Pacific Ocean and stronger-than-normal north-westerly winds off the Sumatran coast.

You may wonder how wind in the Pacific basin can affect sea surface temperatures in the Indian basin, but this example provides a good illustration of how the world's oceans are interconnected.

Those stronger-than-normal easterly winds in the Pacific Ocean - which also caused our late arriving quasi La Niña - created cold water upwelling in the central Pacific while also piling up warm water in the western Pacific.

By way of the Indonesian Throughflow - a north/south current that runs through the straits between the Indonesian islands - the warm water in the western Pacific made its way down through Indonesia, into the Timor Sea and onwards into the Indian Ocean where it influenced local sea surface temperatures.

Meanwhile, stronger than normal north-west winds off Sumatra - with no obvious connection to the Pacific winds - pumped additional warmer-than-normal water in from the north while. Localised north-east wind anomalies also suppressed upwelling off the Western Australian coast.

Wind anomaly from December 1st last year through 8th of February (NOAA)

The North West continental shelf sits right at this convergence zone and has been showing higher-than-normal sea surface temperatures for over three months now. As a result the Leeuwin Current is enhanced, transporting the warmer right down the Western Australian coast, extending all the way around the capes.

While great for surfers this marine heatwave setup has been given a name, that being the Ninglaoo Niño, with it linked to La Niña years thanks to the enhanced Indonesian Throughflow.

Similar to the Pacific phenomena, cooler events are classified as Ningaloo Niña’s and relate to cooler, upwelling events off the Western Australian Coast.

The Ningaloo Niño has a wide influence on the regional climate and ocean biodiversity, with it being detrimental to local fisheries and sensitive coral reef species. On the plus side it brings increased rainfall and moisture to the otherwise arid north-west as we’ve seen the past two months.

The below chart shows the north-west of Western Australia has seen above to very much above average rainfall over the past two months.

For surfers, the warm temperatures should persist into autumn before starting to dissipate into winter.

Rainfall deciles for the period December through January (BOM)