Congratulations @adele-morrison.bsky.social !!! Awarded the IAPSO ECR Medal in Busan today!! Amazing accolade for an exceptional scientist and all-round great person.

And global warming played a big part as well, by shoaling the ocean surface mixed layer steadily over the past several decades. Shallow mixed layers stack the odds of more frequent and severe marine heat waves - same basic ocean physics as described above.

We further decompose the relative contributions from shallow mixed layers, vs. solar radiation, and test shipping emission effects by adding an additional 1 W/m2 to the solar radiation flux. An effect is detectable, but only localised. Weak winds and shallow mixed layers were the dominant cause.

Turns out the incoming solar radiation was also above average in some locations, but not enough to be the main driver of the basin-wide heatwave. Below, red = where solar radiation anomalies dominate, blue = where shallow mixed layers dominate. More details of this analysis in the paper.

Weaker winds mean shallower mixed layers during summer. And shallow mixed layers heat up much more rapidly than deep mixed layers, even if the incoming atmospheric heat fluxes are no different to normal summertime conditions.

But that’s not so surprising considering the advective time-scale to move heat from the tropics to the sub-polar region. What's more interesting is determining the contributions of the various forcing agents that determine air-sea heat fluxes. Turns out a dramatic slowing of surface winds was key.

So was this a sign the overturning circulation had reinvigorated? Or was something else going on? Turns out the latter: air-sea heat fluxes were controlling the warming. Ocean circulation effects, mainly vertical mixing, were actually acting to damp out the warming.

Charts like this started appearing across social media. "Off the charts" suddenly had a literal usage:

It quickly became clear there was a strong reversal of the historical cooling trend playing out in that region, in just a matter of months. By June, the cold blob had warmed to around 2 degrees Celsius above average.

The project got started back in July 2023 when we met as a team to analyse the North Atlantic “cold blob” – how deep it reaches and how robust it is as a measure of the strength of the Atlantic meridional overturning circulation.

Out today in Nature, our paper on the drivers of the record 2023 summer heating of the North Atlantic. Temperatures warmed to record levels in just a few months. The impacts on climate & ecosystems were severe. A thread on how this work came about and what we found.👇👇🧵 www.nature.com/articles/s41...

Submitted! Our application for a new ARC Centre of Excellence focused on our changing oceans has been submitted! Thanks to my amazing team of CIs who put in a big effort over the past 12 weeks since news we’d been shortlisted, capping off a 3 yr period of planning & workshops preparing for the bid!

This Sunday at Bondi Beach Pavillion: Q&A on ocean warming and other climate change impacts on our oceans.

www.afr.com/policy/energ...

Ocean warming has become so significant it’s now a semi-regular feature of TV weather reports here in Australia. A warmer ocean bleaches corals, raises sea levels, melts ice caps, stresses ecosystems, drives flooding rains and amplifies humidity. None of this is good news.