9th Oct – Nippy northwest, pollution on the peninsula

SST update

We’re nearly halfway through spring, and sea surface temperatures are on the rise. It is now warmest in the tropical north, with Darwin’s inshore temperatures topping 30°C, while the Coral Sea and Great Barrier Reef are enjoying typical surface temperatures for this time of year. There’s a large warm region off the Gold Coast, stretching about 400km east, where a warm core eddy is forming.  Cool to neutral in the bight.

The biggest change in the last week or so has been the sudden end of the marine heatwave on the northwest shelf. At the end of last week, temperatures were in the 90th percentile across a broad region, due to record-breaking early season air temperatures and little cloud cover. Strong, sustained offshore winds picked up at the beginning of October, and now parts of that same region are enjoying ocean temperatures well below average, at least on the surface.

La Niña – what’s in store?

La Niña is now underway in the tropical Pacific, with all climate models surveyed by the Bureau indicating that thresholds will be sustained into 2021. For Australia’s oceans,this increases the likelihood of warmer northern oceans, tropical cyclones and Ningaloo Niño events, while confirming none of them.

Australia’s last La Niña event was from 2010 to 2012, with peaks over successive summers. Despite the predictions, tropical cyclones were not more numerous, though a higher proportion were more severe than normal.

However, the prediction of warm oceans and a Ningaloo Niño came to pass. 2011 (the strongest La Niña peak out of the two concurrent events) saw a warm Indonesian Throughflow drive an unusually warm and strong summer Leeuwin Current, resulting in a Ningaloo Niño. Sea surface temperatures along the WA coastline were up to five degrees above average over February and March of that year, resulting in coral bleaching, large-scale seagrass die-offs and a decimation of the abalone population.

Watch this space.

Sea surface temperature anomalies during 21 February – 6 March 2011 at the peak of the extreme warming event. Source: Nature, La Niña forces unprecedented Leeuwin Current warming in 2011, Feng et al, CSIRO.

Mystery of mass marine kill

Last month, reports of surfers becoming unwell after entering the water at Khalaktyrsky Beach near the Russian city of Petropavlovsk-Kamchatskiy surfaced on social media, before dead seals, octopi and other marine animals began to wash up on the shore. Initally played down by officials, this is now starting to look like a case of widespread catastrophic marine pollution along the coastline.

Foam in the sea off the Khalaktyr beach on the Kamchatka peninsula. Source: Greenpeace/AFP/Getty Image

The source remains a mystery; both phenols and oil products have been found in water samples. While a state-run news agency sstated a commercial oil tanker was probably to blame, others suggested the military had dumped waste into a local river, while there was also speculation over a nearby decommissioned chemical waste dump, which for some reason is situated at the foot of an active volcano.

The fact that such a wide variety of marine creatures has been affected is a sign that the pollution extends down the water column, and is not confined near to the surface.

At the time of the initial social media reports, OceanMAPS analysis shows the ocean was unusually warm (and is currently still well above the seasonal average), which one could speculate would have helped phenols to dissolve and mix in the water, thus spreading deeper and further.

Offshore of Khalaktyr beach, the cold East Kamchatka Current flows southward to form the Oya Current. Depending on the source, the quantity of pollution and the level of future transparency from officials, this event may become even more devastating than it already appears to be.

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