SOM AMO PDO Ocean Time Lags And Natural Variability

The oceans have many “modes” or long term states that change from one pattern to another. We still do not know all of them, and those we do know, we don’t understand well. Yet these “modes” change the ocean pattern of temperatures, the winds, the currents, and eventually both our weather and climate.

I’ve run into a couple of papers that point to linkages between the AMO, PDO, and the Southern Ocean.

AMO – Atlantic Multidecadal Oscillation
PDO – Pacific Decadal Oscillation
and a new one to me
SOM – Southern Ocean Mode

This paper looks at the SOM and finds a 40 to 50 year variability in ocean heat content. It also finds that the model of this property is strongly controlled by the degree to which your model understands “eddies”.

A Southern Ocean mode of multidecadal variability

First published: 7 March 2016


A 250 year simulation of a strongly eddying global version of the Parallel Ocean Program (POP) model reveals a new mode of intrinsic multidecadal variability, the Southern Ocean Mode (SOM), with a period of 40–50 year. The peak-to-peak difference in the global ocean heat content within a multidecadal cycle is up to 60 ZJ. This change results from surface heat flux variations in the South Atlantic and propagation of temperature anomalies along the Antarctic Circumpolar Current and into the Weddell gyre around 30°E. The temperature anomalies propagate as deep as 5000 m along the isopycnals between 50°S and 30°S and induce multidecadal changes in the Atlantic Meridional Overturning Circulation. A positive feedback loop between the generation of eddies through baroclinic instability and the dynamics of the mean circulation is essential for the existence of the SOM. The dominant physics appears similar to that responsible for variability found in a three-layer quasi-geostrophic eddy-resolving model. This combined with the fact that the SOM is not found in a noneddying version of the same global POP model further suggests that eddy processes are crucial for its existence and/or excitation.

The actual article is pay-walled, so unavailable to me. We’ll have to make do with the abstract, leaving the actual article as a “Dig Here!” for others.

Note that despite being a “mode” of the Southern Ocean (cycling around Antarctica), it changes GLOBAL ocean heat balance. Temperatures change up to 5000 m deep (call it 15,000 feet) along lines of the same density (isopycnals).

Eddies are critical to this process showing up in the model.

Now think about this for a minute. In “settled science” we are basically ignoring eddies (think ‘hurricane’ in atmospheric models where a 100 mile diameter hurricane is below the level of resolution) yet in this case, eddies are shown to be critical to this particular mode of oscillation of the oceans. For the oceans, this SOM dependency on eddies was only “discovered” in 2016. What other “modes” and dependencies are we still missing, eh?

So just how important is this connection between the “Southern Ocean” and everywhere else?

South Atlantic Ocean and Southern Ocean

Contrary to the North Atlantic, the South Atlantic is largely open to the influence of the southern ocean and other oceans. The Antarctic Circumpolar Current (ACC) allows for inter-ocean transport of heat and freshwater anomalies, permitting ocean route telecommunication of climate anomalies to regions remote from the Southern Ocean at various timescales. The ACC link drives a global thermohaline circulation that is responsible for much of the meridional heat transport in the Atlantic and for shaping the distribution of intermediate and deep water masses. The South Atlantic thermocline exchanges with the Indian Ocean thermocline, and the injection of Pacific-Ocean-derived Antarctic Intermediate and mode water masses in Drake Passage are part of the “warm route, cold route” debate. It is still unknown to what extent the ratio between the cold and warm water route changes across a range of timescales and which processes could determine such a variability.

The exchanges between the Southern Ocean and the Atlantic occur mostly in two very energetic frontal regions, namely the Brazil/Malvinas Confluence, and the Agulhas Current and its retroflection along with the upwelling area of the Benguela Current. Remote sensing data are powerful tools to investigate and monitor system variability at various spatial and temporal scales in these highly dynamic, energetic, and complex regions.

Oh… It ‘only’ drives the whole thermohaline circulation thing and controls meridional heat transport…

I note in passing their placing the Drake Passage in the list of important places and remind folks that I’d pondered the effect of a 400 foot shallower Drake Passage on ocean currents during an Ice Age Glacial cycle / mode. Now here we have one paper saying Drake Passage and the Southern Ocean modes are important to the whole ocean cycling of heat and salinity and another saying little things like eddies are kind of key to it all. Any bets on eddies changing when the Southern Ocean has much more ice in it and is 400 feet shallower with banks further intruding?

How about when the PDO changes. Any impact on things like temperatures on land? And what causes those changes, anyway? Well, as a long duration occupant of California, I remember when The Great Pacific Climate Shift happened. In 1976-77 things suddenly got warmer. We were in the middle of the Oh No New Ice Age!!! Scare then, and suddenly it was gone. Substantially all of the “warming” that the ‘wet briefs crowd’ is panicking over happened in that one shot. So what happened?

This paper is available free and in full at the link so you can read the whole thing if you like.

Decadal variations in the California Current upwelling cells

First published: 21 July 2007


We investigate decadal variations in the three-dimensional structure of the California Current System (CCS) upwelling cells as a potential mechanism for explaining observed ecosystem changes after the mid-1970s. To this end, we track the origin of upwelled water masses using adjoint passive tracers during time periods corresponding to the positive and negative phase of the Pacific Decadal Oscillation (PDO) in a 55 year regional ocean model simulation of the CCS. Results show that in the PDO “cool” phase (pre mid-1970s), the upwelling cell is deeper while during the “warm” phase (post mid-1970s), the upwelling cell is shallower with more horizontal entrainment of surface waters from the north. These changes in the coastal upwelling cell exhibit a latitudinal non-uniformity and may result in significant changes of the nutrient flux, which would have important impacts on the biological productivity of the coastal ocean.

In short, The Great Pacific Climate Shift is now called the PDO, it is driven by the ocean currents shifting, and we now have clue that the ocean currents shifting is driven by the oscillation of the Southern Ocean Mode. This same process drives the AMO, and thus both oceans drive the “Climate Change” via a Southern Ocean modulator.

Now one might ask: What’s the Southern Ocean been doing for the last few thousand years? A nice dig was done here:

New paper finds 5 non-hockey-sticks in the Southern Ocean — Published today in Quaternary Science Reviews

By: Marc Morano – Climate DepotJuly 24, 2013 9:52 AM

New paper finds 5 non-hockey-sticks in the Southern Ocean

A paper published today in Quaternary Science Reviews shows 5 non-hockey-sticks from reconstructions of sea surface temperatures [SSTs] in the Southern Ocean, each of which demonstrates a long-term cooling of the Southern Ocean over the past 8,000 to 10,000 years.

Prior posts on non-hockey-sticks

Second through 6th graph from the top show sea surface temperature reconstructions from the Southern Ocean, each of which show a cooling over the Holocene [past ~11,000 years]. Horizontal axis is years before the present.

A review of the Australian–New Zealand sector of the Southern Ocean over the last 30 ka (Aus-INTIMATE project)

H.C. Bostock et al , How to Cite or Link Using DOI

Permissions & Reprints


The Australia/New Zealand region of the Southern Ocean is influenced by several of the major global water masses of the oceans and is the prime entry point for cold deep waters into the Pacific basin. During the last glacial there was increased sea-ice extent around Antarctica (as far north as 55°S), as well as increased iceberg presence inferred from ice-rafted debris. Evidence from microfossil assemblages suggests that sea surface temperatures (SST) were up to 7 °C cooler, consistent with recent estimates of cooling for New Zealand derived from glacier modelling and other terrestrial proxies. The Subtropical Front (STF), Subantarctic Front (SAF) and Polar Front (PF) had migrated north, except where the position of the fronts were controlled bathymetrically. Despite the potential for iron fertilisation by increased dust input into the ocean during the glacial, there is limited evidence for higher total biological productivity in the Pacific sector of the Southern Ocean. The altered oceanic circulation during the glacial also decreased nutrients in the surface waters and affected the outgassing of CO2. This contributed to an increased storage of CO2 in the deep waters and lowering of the carbonate lysocline.

During the deglaciation, sea-ice retreat and SST increased rapidly at ∼18 ka, roughly synchronous with the reinvigoration of deep water circulation in the Southern Ocean and the release of CO2 stored in the deep waters. The gradient in carbon isotopes (δ13Cbenthic) between Antarctic Intermediate Water (AAIW) and lower Circumpolar Deep Water (LCDW) was greatest at the start of the deglaciation, suggesting that the AAIW ventilation preceded LCDW ventilation, or there was a significant change in air-sea fractionation of δ13C. There was a slight enrichment in δ18Oplanktic, decrease in SSTs and a reduction in intermediate and deep water circulation between ∼14 and 12.5 ka BP during the Antarctic Cold Reversal (ACR), coincident with glacier advances in the New Zealand Southern Alps and other terrestrial records of cooling. Following the ACR, there was a second, more minor, release of deep water CO2, most likely related to reinvigoration of North Atlantic Deep Water (NADW). From 10 ka onwards the modern intermediate and deep water circulation was established.

Air temperatures and SSTs reached a maximum in the early Holocene, with the STF located at its most southerly position, and there was a widespread retreat of Antarctic ice sheets to their modern position. A decline to modern SST and air temperatures in the mid to late Holocene followed. While millennial cycles overprinted on the SST and δ18Oplanktic records, may be the result of subtle changes in the position and strength of the westerly winds during the Holocene.

So we have confirmation that overall, the Southern Ocean reflects what we know from the ice cores: It’s been generally cooling for a few thousand years, but we have some oscillations riding on top of that which can cause temporary warmer or colder cycles of about one lifetime (well, 50 ish years but most folks are not paying attention the first 10 to 20 years of their life, so one “awareness lifetime” ;-)

So the main climate driver of the oceans shows a general cooling. The PDO and AMO flipping changes cyclic weather. We know they flipped to a warm phase (for the PDO back in ’76-’77) and are both starting to look like a cold flip is in our immediate future. All of “Global Warming” can be simply attributed to a natural oscillation of the Southern Ocean driving the AMO and PDO into warm cycles; and that cycle is now ending.

How AMO / PDO correlate with temperatures:

What’s happening now with the AMO:

Meteorologist Predicts Atlantic Cooling

Something significant is occurring in the Atlantic Ocean, according to meteorologist Paul Dorian of US weather forecast service Vencore Weather – Atlantic cooling. This graph shows the observed Atlantic Multidecadal Oscillation index, for the period 1870-2015. Courtesy: NCAR

Posted By: Site Admin May 10, 2016

Something significant is occurring in the Atlantic Ocean, according to meteorologist Paul Dorian of US weather forecast service Vencore Weather – Atlantic cooling. Evidence is growing to support predictions that the Atlantic Ocean is in a cooling phase and is set to cool further over coming decades with weather impacts for northern Europe and the north western US. Dorian is not the first scientist to reach this conclusion and he has put his thoughts into this article which was posted on the Vencore Weather website.

by Paul Dorian, Meteorologist, Vencore, Inc.

In addition to solar cycles, temperature cycles in the planet’s oceans play critical roles in our ever changing climate and also on the extent of global sea ice. Oceanic temperature cycles are often quite long-lasting and a warm or cold phase can persist for two or three decades at a time. In general, the Atlantic Ocean experienced a cold phase from the early 1960’s to the mid 1990’s at which time it flipped to a warm phase and that has continued for the most part ever since. The current warm phase; however, is now showing signs of a possible long-term shift back to colder-than-normal sea surface temperatures (SST) and this could have serious implications on US climate and sea ice areal extent in the Northern Hemisphere.

So there’s your “Global Warming” in a nutshell. PDO flipped to warm in 1976 and then AMO followed in the 1990s. Peak “warmth” in sync. Now the AMO is flipping back to cold. What about the PDO?

NASA: PDO flip to cool phase confirmed – cooler times ahead for the West Coast?
Anthony Watts / April 29, 2008

A cool-water anomaly known as La Niña occupied the tropical Pacific Ocean throughout 2007 and early 2008. In April 2008, scientists at NASA’s Jet Propulsion Laboratory announced that while the La Niña was weakening, the Pacific Decadal Oscillation—a larger-scale, slower-cycling ocean pattern—had shifted to its cool phase.

This image shows the sea surface temperature anomaly in the Pacific Ocean from April 14–21, 2008. The anomaly compares the recent temperatures measured by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) on NASA’s Aqua satellite with an average of data collected by the NOAA Pathfinder satellites from 1985–1997. Places where the Pacific was cooler than normal are blue, places where temperatures were average are white, and places where the ocean was warmer than normal are red.

The cool water anomaly in the center of the image shows the lingering effect of the year-old La Niña. However, the much broader area of cooler-than-average water off the coast of North America from Alaska (top center) to the equator is a classic feature of the cool phase of the Pacific Decadal Oscillation (PDO). The cool waters wrap in a horseshoe shape around a core of warmer-than-average water. (In the warm phase, the pattern is reversed).

Given that the “outgassing” of CO2 is controlled by water temperatures, I’d suggest watching for changes in CO2 level as we start having ice cold rain doing “counter current stripping” of CO2 from the air and into the oceans. It is likely to take a while for that to start, though. First, much of the ocean cooling has yet to complete, and then the air must get quite a bit colder as the cold phase reaches maturity. Somewhere in there, the cold water CO2 stripping will be active and the oceans cold enough to entrain that CO2 into the deeps.

As PDO / AMO processes are very slow, it will take on the order of a decade or two for the effect to build. At this time, all we need is a decent “holding action” against the Warmistas and a good decade thwarting of their efforts to put the economy into a CO2 noose. Sometime in the next half decade, I’d guess, we’ll need to start attacking the crazy idea that “Warming is causing all the snow”… but I think that won’t be too hard to do. Most folks are pretty clear on the idea that frozen is not warm ;-)

Sidebar on Links:

I’d had a couple of other links per the Southern Ocean influence on AMO and PDO, but somewhere along the line I lost them. Should I find what browser on which device has them, I’ll add them here. Searching for PDO / AMO / Southern Ocean linkages with temperature is a fruitful “Dig Here!” for anyone wishing to understand what’s really going on in climate and weather shifts. The Southern Ocean Mode is, IMHO, likely driven by the longer duration tidal shifts from the Saros Cycle interaction and from lunar / solar alignment shifts of tides. Pulling much more water further South in some cases, north in others. Exceedingly long term, as the obliquity of the earth shifts, those alignments will also change tides and thus the SOM, perhaps via changes in how eddies act when water is deeper, shallower, or pulled around differently. Some digging on lunar / tidal impacts on ocean eddies might well be productive.

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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11 Responses to SOM AMO PDO Ocean Time Lags And Natural Variability

  1. philjourdan says:

    Like you, I am easily distracted. IN researching (or reading) about one thing, my mind wanders.

    I understand how the oceans play a critical part in our climate. More so (I think) than man ever could. But this got me to thinking about the time when there was but one great ocean (Pangea times) and how that affected the weather. It is not something that can be tested, but I am sure even with just a single ocean, there was impact. If they ever get back to science, we may get some good insight into how it did affect climate.

    As for the delaying action, I probably will not be around to see the turn. So I expect we will simply freeze to death from record heat.

  2. Bill Dawson says:

    First time poster. Just wanted to thank you for the many years of enjoyment in reading ALL of your posts on a variety of subjects especially climate change. I admire your mind power and the breath of your thinking. Thought it was just time to thank you. Please don’t leave us – you’re too valuable a resource.

  3. wyzelli says:

    You may recall I previously referred you to in relation to lunar drivers of ENSO. Paul has recently posted similar analysis of AMO and PDO, which add weight to all of these oceanic systems being stongly driven by lunar gravitational forces. Interesting reading.

  4. Pingback: SOM AMO PDO Ocean Time Lags And Natural Variability – Climate Collections

  5. E.M.Smith says:

    @Bill Dawson:

    You are most welcome! I’ve no plans on “leaving”, but nature sets the alarm clock…

    Ideas just percolate for a while, then push their way, fully formed, to the top. In many ways I’m just a passenger along for the ride too… Sometimes I know what’s interesting to me and what’s coming next, sometimes it just shows up ;-) As I’m afflicted with “novelty seeking behaviour”, I can’t stand the idea of sticking to just one set of thoughts and calling it done. Just can’t stand the boredom of it. It’s just what I am.


    Just one great ocean lets both poles become warm. Currents and modes dramatically different.


    Yes, though I’ve not had enough time to fully dig into the site; it all looks like good stuff.

  6. John F. Hultquist says:

    I’ve read lots of things about the PDO, and especially like the many posts Bob Tisdale did a few years ago. In Bob’s posts the PDO “appears” out in the North Pacific west of the State of Washington, where I live.
    With that in mind, consider the recent snow in Seattle was 2nd earliest in the City’s weather history.
    Link Scotts weather blog

    Further, today, Chinook and Cayuse Passes — just east of Mt. Rainier — have been closed for the season. This is perhaps 3 weeks sooner than is often the case. I’ll get around to checking, but have other things that need doing right now.

  7. A C Osborn says:

    Isn’t it refreshing to see that some “Climate Scietists” are still actually doing real Scientific Work.
    No CAGW agenda, just old fashioned science.

  8. E.M.Smith says:

    @John F. Hultquist:

    IMHO, it’s all about circular 3 D processes. From dust devils to hurricanes to eddies and gigantic ocean gyres and then circumpolar vortex and equatorial trade winds. When these are stronger, we get “meridional” flow of air and the attendant swings from hot to cold as the Lava Lamp blobs flow each way. I think something similar happens with water flow.

    The big missing piece being just how deep and what temperature are the various ocean layers. Start churning up deep cold water off California (where we already have some rising cold water currents) and it gets even colder. Leave it with a thin but warmer surface layer, it is warmer.

    That, IMHO, is THE thing most missing from ALL the “climate” models. They are based on square boxes. It’s hard to fit a round process circular peg into a square box model hole… They think in layers and squares while the world works in vortexes and circles.

    IMHO, the cold will show up first as lots of rain as the (relatively) warmed ocean cools by evaporation. Then that rain will slowly turn to snow at ever lower altitudes and latitudes as the air gets cold enough (thanks to the lower atmosphere height and more effective radiation of heat from the Polar Vortex areas). Then that snow begins to stick, year over year… So first floods, then heavy snows, then ice accumulation.

    The unclear part is will that ice continue to accumulate for 100,000 years, or will it start melting again in another 30 years, or another 179, or another 300…

  9. David A says:

    Hum??? Good post again!

    So the wee little atmosphere, sandwiched between powerful, cycle changing EM radiating solar variation, and great oceans with 1000 times the energy of the atmosphere, all of it swirling churning and convecting at disparate rates, changes climate all by itself. ( This leaves CO2 as chump change in the mix)

    So 4 or 5 major ocean currents all cycling at different rates which occasionally align to different degrees, creating dramatic shifts in weather over 30 or so year periods, against a background of much longer cycles, all subject to solar variations of disparate affects from the top of the atmosphere to the depths of the oceans which take up to a thousand years to overturn. Sounds like a good summary.

    Well the PDO shift to cool had paused, but appears to have resumed, while concurrently the AMO had appeared to make a definite shift downward, yet has recently swung back up before its likely multi decade downward cycle resumes. ( nothing out of the ordinary if one looks at unsmoothed annual PDO and AMO flux)

    When the two have a strong downshift together, as appears likely over the next several years, then natures observations should overwhelm bureaucratic spin.

  10. Larry Ledwick says:

    Speaking of long term weather cycles. NYC set to break a 60 year old low temperature record

  11. Lurking says:

    ” Some digging on lunar / tidal impacts on ocean eddies might well be productive.”

    Try this. “The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change ”

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