2014, 2015 and 2016 played a recurring theme of El Nino. A tentative El Nino in late 2014 and early 2015 segued with a stutter into a strong El Nino in 2015/2016 dragging global temperatures in train. Temperatures in the tropical Pacific dropped a bit after that and may or may not have slipped into La Nina depending on which agency you listen to, but now, it looks like El Nino might be coming back: surface water temperatures in the eastern Pacific, off the coast of South America, have risen to four or more degrees above average although they’ve not spread further west and a number of seasonal forecasting centres are suggesting that temperatures might continue to rise. No one’s called it an El Nino, yet, but the effects of the elevated sea-surface temperatures are sadly plain to see. Heavy rain in Peru has already led to flooding and all the misery that brings.
The animation shows the evolution of sea-surface temperature anomalies from September 2016 to mid March 2017. The elevated SSTs in the east towards the end of the animation are very clear.
As far from the tropics as one can get, other unusual things have been happening. After a long series of record lows at both poles – at least for the time of year – Antarctic sea ice reached its annual minimum, dropping to a record low extent and, just a few days later, Arctic sea ice reached its annual maximum. It was the lowest maximum extent on record. The record isn’t extremely long in this case as satellite monitoring only began in the late 1970s. The second video shows sea ice concentrations and sea-surface temperatures at both end of the Earth in 2017 so far. The low ice extents in the Arctic have been accompanied by unusually high temperatures for the region and time of year.
The final video for tonight shows sea-surface temperature anomalies in the vicinity of Australia. There are a number of things to note – the persistent cool anomalies off the south-west of the country, the beautiful looping current off the coast of New South Wales – but one of the more striking and troubling is the area of higher-than-average sea-surface temperatures off the north east coast of Queensland in February and March. This is the area in which the Great Barrier Reef is to be found. High water temperatures can, and have, led to bleaching of coral in some areas for the second consecutive year.