Ocean news

The East Pacific has been cooling for a couple of decades, it turns out. A “warming hole”, we have to call it. Persistent strong trade winds are part of the reason. Chinese researchers have also found that, in their words:

“a persistent cooling in the eastern Pacific is directly linked to an eastward displacement of the Southeast Pacific Subtropical Anticyclone (SPSA). Interactions between the Andes and an eastward shift of the SPSA generate greater pressure gradients in the eastern flank, in turn, stronger alongshore winds and more intense upwelling …”

Here’s the paper: https://iopscience.iop.org/article/10.1088/1748-9326/abd819/meta

One suspects that the ongoing cooling of the Humboldt current from Antarctica north along the western South America’s coast is also part of the cause:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080634

https://www.sciencedirect.com/science/article/pii/S0079661116300325

Elsewhere, South African scientists studied the responses of Sparid reef fish to either warming or cooling outside of their normal water temperatures. They found that stress was encountered more quickly by cooling than by warming of their surrounding water:

https://www.tandfonline.com/doi/abs/10.2989/1814232X.2021.1922501

The Sparidae, a family of Perciform reef fish

Substantial sea surface cooling events associated with the Madden Julian Oscillation appear to be getting more frequent recently, such as the one in the Banda sea to the east of Indonesia in 2015:

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021JC017226

Meanwhile the Southern ocean south of latitude 55 has cooled also in recent decades, associated with further wind driven spread of Antarctic sea ice. This adds a layer of fresher but cold water at the southern ocean surface, which reminds buoyant above warmer but more saline water deeper down. It’s been noted elsewhere that during glacial periods, warm water remains trapped under the greatly expanded sea ice.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019AV000132

9 thoughts on “Ocean news

  1. Upwelling/downwelling is responsible for the pattern of sea surface temperature anomalies observable here: https://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-249.16,-38.72,1886/loc=-35.674,-44.448
    The temperature of the waters south of the Galapagos Islands is a good proxy for sea surface temperature globally, and since the ocean is by far dominant in terms of surface area, the march of global temperature.

    SST in the Galapagos is strongly related to the air pressure gradient between the Chilean High and the Maritime continent to the north of Australia. Alternatively its well mapped by the evolution of the pressure gradient between the Chilean High and the Galapagos itself.

    These pressure gradients are a response to shifts of atmospheric mass from the Antarctic trough, the Aleutian Low and the Icelandic Low, the most volatile of these in the short term being the second, perhaps due to the concentration and persistence of the Aleutian Low in a fairly localized area, unlike the Icelandic low that competes to some extent with the tendency for Atlantic low pressure cells to migrate from Newfoundland towards Scandinavia. Secondly, the Aleutian is fed with a stream of moisture from the Maritime Continent giving rise to heavy precipitation in British Columbia driving convection via latent heat release. The circulation of the Aleutian is stratospheric in origin with the temperature of the air at 150 hPa inversely related to surface pressure. This cell is a sink for ozone. Partial pressure of ozone is tiny by comparison with CO2 so its well short of saturation delivering a strong temperature response in the upper troposphere.

    The transfer of atmospheric mass from the high latitude lows is evolutionary, over long periods. It gives rise to the southward migration of the Southern Hemisphere westerly winds that corresponds with warming climate over centennial timescales documented here: https://www.nature.com/articles/s43247-020-00059-6

    The short term evolution of the pressure gradient across the Pacific responds strongly to the evolution of the Aleutian Low but on centennial scales, the Antarctic Trough.

    The heart of the matter is related to the pressure and density gradient between the Antarctic Polar Cap and the air over the Southern Ocean between 50 and 70 degrees south latitude at jet stream altitudes where cyclones are generated.

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    1. Thanks Erl – a lot to digest there! The Southern Hemisphere does have most of the oceans’ water so it’s not surprising that it has a disproportionate effect on global climate. I’ll have to do some map reading to get my head around the pressure gradient system.

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    1. Warming and cooling intervals over the Holocene are always accompanied by corresponding increases and decreases in ocean temperatures and heat content – in fact it’s the ocean temperatures that drive climate change, not the other way around. OHC now is still nowhere near what it was at the Holocene optimum, 9000 years ago. What goes up must come down!

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      1. What’s caused ocean temperature / heat change? The same thing(s) that have caused it to change continually for the whole Holocene. Forever in fact. Climate is always changing and that includes – actually starts with – ocean surface temperature change.

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  2. David, note the abrupt jump in the anomaly at 0-100 metres (the illuminated zone) between 1976-78 at the time when the temperature of the upper troposphere and stratosphere responded to falling surface pressure over Antarctica, a cloud cover effect undoubtedly. Sea data at https://www.ncei.noaa.gov/access/global-ocean-heat-content/index3.html and 250 hPa air in September at:
    https://psl.noaa.gov/cgi-bin/data/timeseries/timeseries.pl?ntype=1&var=Air+Temperature&level=250&lat1=-20&lat2=-40&lon1=0&lon2=360&iseas=1&mon1=8&mon2=8&iarea=1&typeout=2&Submit=Create+Timeseries

    It would be instructive to see the change in 0-100 metres by latitude. I suspect its initiated in the latitude band 10-40° south during La Nina episodes when the temperature at 250 hPa hits a peak (reducing cloud cover) and upwelling in the ocean drives sea surface temperature lower. Both effects in response to a decline in atmospheric mass in high latitudes with commensurate increase in surface pressure in high pressure cells globally, including crucially, that in the South East Pacific.

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  3. David, a flippant comment. No alternative thesis presented.

    Consider this: Its the illuminated zone. Much faster ate of warming than 0-700 metres. Warming due to enhancement of solar radiation is the only thing that can account for that sort of increase in such a short interval of time.

    Globally, 0-100 metres represents a substantial body of water. Its most of the zone affected by upwelling/downwelling that gives rise to surface temperature anomalies.

    Would you maintain that change in cloud cover plays no part? Any alternative thesis?

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