The data below shows the evolution of sea surface temperature in the Western Pacific between the coordinates marked in the map below. In this map from https://earth.nullschool.net/ temperature at 20° south is about 26°C and at 30° south its about 21°C. The currents that are visible in the picture indicate its a mixing zone so local temperature depends in part on where the water is coming from. The circulation in the Pacific south of the equator is anticlockwise and can be expected that temperature will reflect the El Nino, La Nina phenomenon.
The evolution of surface pressure across the globe is governed by the Antarctic trough that exhibits a profoundly low and highly variable atmospheric pressure in cycles of between three and four years duration, that evolve within a longer cycle of 80-120 years, in line with solar activity. Since 1948 surface pressure has dropped by almost 10mb in this trough, the heart of which is located on the margins of Antarctica at 60-70° South Latitude. Its the deepest trough in surface pressure on the planet, a sink for the atmosphere, globally. Don’t underestimate its significance.
The intensity of Polar cyclone activity in the ‘Antarctic Circumpolar Trough’ is greatest in August, September, October and November. As atmospheric pressure falls away in the trough, surface pressure builds elsewhere. The Icelandic and the Aleutian Troughs of the Northern Hemisphere are also actors in this play, the northern and the southern troughs like two horses pulling a buggy but unevenly, because the pulling in the Arctic happens only in northern winter and the pull from the Antarctic trough is all year round and peaking between June and November with September a particularly significant month.
By this process atmospheric mass is shifted to the mid latitudes, especially over the ocean in the Southern Hemisphere where high pressure cells of descending air manage the return of air towards the surface of the planet. This changes the winds and flow of water in the ocean including the phenomenon known as ‘upwelling’ that occurs in the eastern Pacific, brings cold nutrient rich waters to the surface and is vital to the fishing industry in the North Pacific (Monterey, ‘Cannery Row’, John Steinbeck) and off the coast of Chile. The Trade winds and the North westerlies that flow from the mid latitude high pressure cells intensify as surface pressure builds in mid latitudes, but since the major trough is in the south rather than at the equator, the westerlies tend to rob the trades of their oomph. That has consequences for the location of the center of convection in the Pacific Ocean. Strong Trades keep the center of convection in the west. Weak Trades are associated with less upwelling of cold waters in the east (fishing industry collapses) and allow the center of convection to move more to the east, further weakening the trades to the west of the center of convection. But only rarely are the trades weakened to the extent that they flow eastwards rather than westwards. This is monitored as the ‘Southern Oscillation’ which is simply the extent to which surface pressure in Tahiti exceeds that in Darwin.
The impact of the Arctic trough is seen at its peak in January. The Aleutian and the Icelandic Lows are active between November and March in changing the distribution of atmospheric mass, the global winds, ocean currents and depleting cloud cover which increases globally from August as the land masses of the northern hemisphere cool, and with the land masses, the atmosphere. As the Aleutian trough deepens the large high that is resident to the west of South America intensifies.
A polar cyclone lifts air containing ozone to the top of the atmosphere. What goes up must come down. As atmospheric mass is shifted from high latitudes to the mid latitude high pressure zone in the southern hemisphere it introduces ozone to the troposphere, a potent source of atmospheric warming and a destroyer of cloud. When this happens over the ocean, energy accumulates in the Earth system. So, how this phenomenon plays out in the southern hemisphere, that is mostly ocean, is vital to the evolution of temperature globally.
Inspecting the figure above one can see that September exhibits less of an increase in temperature over the period as a whole but wider swings between solar cycles (numbered at the bottom with rectangles indicating when they started and how long they lasted. The polynomial curve doesn’t really capture the full variability between cycles. In particular it fails to indicate the descent in sea surface temperature in the change from the weak cycle 20 to the strong cycle 21.
Why did sea surface temperature fall during the strong solar cycle 21? The effect of the interplanetary magnetic field on the rotation of the atmosphere, that influences the strength of Polar cyclone activity, is greatest at solar minimum when galactic cosmic rays are most intense and are influential in ionizing the atmosphere to depth, including the troposphere. A high level of atmospheric ionization within a relatively invariable magnetic field (few solar eruptions at solar minimum) will promote the rotation of the atmosphere which moves in the same direction as the Earth but faster, and nowhere faster than in high southern latitudes in winter. Think ‘electric motor’. At solar minimum a fast solar wind comes from high sun latitudes, while at solar maximum, the solar wind is dominated by a slow and variable wind from all solar latitudes that is grossly disturbed by coronal mass ejections, introducing flotsam and jetsam (highly charged particles) that spiral out into the interplanetary environment. It follows that the Interplanetary Magnetic field is less coherent in strong solar cycles and at solar maximum.
The Earth’s atmosphere couples most strongly with the interplanetary magnetic field when the axis of the Earths rotation (a line from pole to pole) is at 90 degrees to its orbit of rotation in March and September. Hence the significance of September that lends weight to what’s happening in the Antarctic trough in September. It can be demonstrated that September is the organizing month for the evolution of temperature at all latitudes. But not now.
It is in strong solar cycles that Galactic Cosmic rays penetrate the atmosphere to the least extent. So, in a strong solar cycle the atmospheric condition, the extent to which atmospheric particles carry an electric charge, is subdued. The ionization picture is not simple because ionization also depends on the variation in short wave ionizing radiation from the sun that peaks at solar maximum and secondly the variation in the partial pressure of ozone that is affected by the intake of mesospheric air over the poles in winter. Ozone partial pressure peaks in winter but that’s also when the intake of mesospheric air occurs. However, as pressure falls in high latitudes, the intake of mesospheric air falls away and allows ozone partial pressure to build. That works to intensify the polar cyclones. It’s a built in feedback that magnifies change. Its like putting your foot on the accelerator and someone pushing down on your knee at the same time. Whoopsie, here we go.
The upshot is that solar minimum and weak solar cycles produce change in sea surface temperature in the Western Pacific and across the tropics generally. The sign of that change will depend on whether the solar wind, that reverses polarity at Hale cycle intervals, favours or retards the rotation of the atmosphere. The trend in sea surface temperature is currently posting a warning that cooling is imminent. A new Hale cycle is underway.
It’s apparent from the timing of peaks and troughs that solar minimum always introduces a steep change in the evolution of sea surface temperature. The fingerprint of each cycle, as it appears in the month of September is different. It’s apparent that solar minimum is a time of abrupt and extreme change in sea surface temperature.
Peaks in sea surface temperature in September signal change in January. It looks as if January puts the candles on a cake baked in the winter months. There is nothing random or chaotic about the way sea surface temperature changes. This is an organic system. It’s not dependent on the flap of a butterflies wings in the Amazon.
A decline in sea surface temperature is likely in the coming Hale Cycle (two eleven year cycles) and it will be as abrupt and severe as that between Cycle 20 and 21. September leads the way.
Cool springs are bad news for grape growers and wine makers. Grape-growers in the northern hemisphere have been reminded of this in recent months. Here in Margaret River a slow build in temperature in spring makes for light crops and later vintages. Frost damage is almost unheard of. But, last winter we had snow on Bluff Knoll in the Stirling ranges That’s rare. 1999 and 2006 stand out as cool vintages and that is reflected in January and April temperatures in the data above.
My preferred fuel is diesel. When I want instant heat, I mix it with petrol. I just hope we never run out because the power coming out of my solar array is pathetic. I’ve tried both solar and wind and learned my lesson the hard way. If you think bending over the bonnet of a car is bad for your back think about the risks attached to cleaning solar panels on a sloping roof eight metres up in the air, no safety net, and concrete below. When I signed up and took the subsidy from the ever generous taxpayers, I didn’t realise I was agreeing to run a power station that splutters and dies on a daily basis.
Here endeth the lesson for today. I have underlined the important bits. If any of this argument is obscure please let me know. You need to prepare for cold. Hint: don’t let them close down the coal mines.
Sea surface temperature data is from: https://psl.noaa.gov/cgi-bin/data/timeseries/timeseries1.pl