Continuing to expand the horizons of the Globe Earth on which we all live is a pursuit I enjoy as as a weekend hobby as well as way of life. This includes subjects like climate and weather and an overall clearer understanding of the paleoclimatic record to better appreciate the small blink of time that we currently find ourselves existing in.
The topic of Ice ages is of particular interest because the current explanation of Ice age timing , although reasonable, appears not to be particularly accurate or predictive in nature.
Looking at the graph below it would appear that in the not so distant past , large temperature swings were not nearly as common as they are today.
I have “blocked out” and overlaid approximately 800,000 year “windows” that each show markedly different types of temperature fluctuations over this 5 million year proxy from sediment reconstructions. Each block highlights a visual change in frequency , slope or amplitude. These are windows are arbitrarily created and are heavily biased by my own creative choice and pattern recognition. The most recent block (far left) has the largest swings and a lengthening frequency between cycles and this is the glaciation period I will be focusing on. It would suggest, from a glance at the trends, that a colder world with deeper cycles and longer periods between “interglacials” is becoming the norm.
Now lets take a closer look at this last 800,000 year period in some finer detail. These graphs, outlined below, are strewn across the interweb in a variety of forms and formats. This one below is from a NASA site and I will reference several others as we go.
(Note it has “now” on the right instead of the left as in the above chart)
Here we note that a 10c temperature fluctuation is not the least bit uncommon but in fact the norm. note that after a sharp spike and short pause there is a long, slow decline to a prolonged colder valley. The short pause we call an interglacial. My question is not”why the trend to a continued colder climate” but instead “what might trigger this sudden “melt” and warming in an otherwise downward cooling trend. It is a lot of heat, after all that is needed to break a high albedo, snow covered earth and start melting massive amounts of Ice that have taken many thousand years to accumulate. It’s easy to see the saw tooth pattern in the graph above when highlighted and accented in the graph below. This sawtooth waveform is not present, or even possible by definition in the previously accepted Milankovitch cycle due to the additive sine functions of orbital fluctuations.
Note in the above graph how there has been a change from shorter more frequent cycles in the past to longer deeper cycles over the more recent 450,000 years. Its unclear if there is a buried , declining secondary cycle or a move to a much stronger first melt followed by a less impressive secondary melt.
What I am looking for is some combination of orbital parameters that can trigger the “melt phase” and which then subsides for a period until repeating this cyclic pulse heating phase. This is not unlike like a home furnace that cycled on and off.
Looking at only two of the many orbital parameters first proposed by Milankovitch (Figure 4) Here we have orbital eccentricity ( red dashed) and net solar insolation( 65N, black solid). Net insolation is ultimately derived from a host of other orbital parameters, but I will show here, how it is a secondary driver of the smaller fluctuations.
Some other features of the graph below(fig 4); vertical yellow lines (trigger intersect) vertical green lines are calibration dates. These lines run through all subsequent graphs as reference points.
So how did I select the yellow trigger bands? These lines were chosen to always intersect a positive change in orbital eccentricity , combined with a positive rise in net insolation. In order to get a hard spike and the sawtooth pattern we need to use “rate of change”(slope) for both values and not just the current net value.
I derived a fairly simple calculation based on this and produce (Figure 5). The blue line is the temperature forcing based on this and represents when the heat is “turned on “. Again, note how the yellow trigger bands are largely located at the onset of the interglacial warming spike. I would call the blue line a “heating curve” showing when the heat is turned on and when its not. It has then been displaced 23,000 years in order to turn it into a temperature proxy. this sounds like a long time but is relatively short when melting thousands of vertical feet of glaciation.
There is close correlation to the calculated cyclic action (primary and secondary waves) but the overall magnitude is not particularly well represented. In other words, I can say “when” but not exactly how big due to a poor understanding of all the other factors in play.
Now, lets compare the “heat cycle” from figure 5 and the yellow “bins” that contain each glacial period to ice core data. I have used the green vertical lines to mark a “now” and 400K calibration point so multiple records and proxies can be more easily compared and stitched together on non-conforming graphs.
There is a slight shift in the exact alignment with time but then it needs to be considered that Glacial ice layer timing may be more variable in calibration than orbital cyclic timing. Several thousand years of variation is easily possible unless secondary calibration methods are employed.
Moving forward we can have a quick look at what predictions we might make from this. for example, when and how long will the next cold snap last and when can we expect relief. Looking back at Figure 4 you can see that the orbital data indeed extends into the future.
In Figure 7 below the green line to the left is today (now) and we’re just starting on the way down that cooling hill into the next abysse. I see 48,000 years with no big heating periods. – Maybe a tiny “blip” secondary recovery at the 12,000 year mark but that won’t melt much ice.
This whole exercise is not particularly important or significant when a human life span is measured in decades -not millennia – and nobody today will ever know if this cyclic and heating cooling prediction is correct. It may however raise some questions and lead to a better understanding of the geological and astrophysical parameters that may be at play.
I have only dabbled briefly with this entire concept and i’m sure there may be better ways to approach the problem and better orbital parameters to choose from and algorithms to resolve.
Why would positively accelerating and increasing orbital eccentricity create such a powerful heating cycle?
What process could be involved?
If this is a heat source rather than an a climatic positive feed back loop,
Is the source internal or external to the planet?