Arctic Ocean To Close, Polar Bears Doomed
A new theory of supercontinent formation, published in the journal Nature, predicts that the Arctic ocean will be squeezed out of existence in the future as most of Earth's landmass gathers in a new supercontinent—Amasia. The new orthoversion helps to resolve the problems of the older introversion and extroversion models, which have led to a “fundamental disconnection … between the geologic evidence for supercontinent formation, and the models purported to explain their assembly.” If the Arctic Ocean disappears so will the Polar Bear, an iconic species that has been held up as a poster child for global warming. The climate catastrophists are correct in predicting the demise of the white bear of the Arctic, but they have both the reason and time frame terribly wrong.
Tracing the formation and breakup of so called supercontinents back nearly two billion years, a team of Yale researchers have devised a new theory of how and where supercontinents form. Ross N. Mitchell, Taylor M. Kilian and David A. D. Evans looked at the transitions for the last three supercontinents—Nuna, Rodina and Pangaea—and concluded that new supercontinents tend to form 90° away from their predecessors. Here is how they summarized their findings in the report abstract:
Traditional models of the supercontinent cycle predict that the next supercontinent—‘Amasia’—will form either where Pangaea rifted (the ‘introversion’ model) or on the opposite side of the world (the ‘extroversion’ models). Here, by contrast, we develop an ‘orthoversion’ model whereby a succeeding supercontinent forms 90° away, within the great circle of subduction encircling its relict predecessor. A supercontinent aggregates over a mantle downwelling but then influences global-scale mantle convection to create an upwelling under the landmass. We calculate the minimum moment of inertia about which oscillatory true polar wander occurs owing to the prolate shape of the non-hydrostatic Earth. By fitting great circles to each supercontinent’s true polar wander legacy, we determine that the arc distances between successive supercontinent centres (the axes of the respective minimum moments of inertia) are 88° for Nuna to Rodinia and 87° for Rodinia to Pangaea—as predicted by the orthoversion model. Supercontinent centres can be located back into Precambrian time, providing fixed points for the calculation of absolute palaeolongitude over billion-year timescales.
It should be noted that the continents are never standing still, but in constant motion. Once called continental drift but nowadays referred to as plate tectonics, the plates that comprise the Earth's crust continue to pull away from each other in some places and crash together in others. On occasion the continents they carry all huddle together, forming a single gigantic landmass—a supercontinent. Of the three supercontinents mentioned above Nuna (also referred to as Columbia) was at its peak 1.8-1.5 billion years ago, Rodin 1.1-0.7 billion years ago and Pangaea, the most recent, 300-180 million years ago. The two older theories that attempt to explain supercontinent formation are introversion and extroversion. The predictions made by the three theories are shown in the figure below.
To test between introversion (0°), extroversion (180°), or orthoversion (90°) models of the supercontinent cycle, the authors quantitatively determined the centers of supercontinents and measured the angular distance between successive supercontinent centers. As a result of these analyses: “Using our orthoversion model, we find that Pangaea orthoverted from Rodinia, and Rodinia orthoverted from Nuna. Extrapolating this model into the future, Amasia should be centred within Pangaea’s subduction girdle.”
The predicted scenario using orthoversion is shown in panel c, where the continents squeeze together at the top of the globe, closing the Arctic basin. Obviously, polar bears, who exist by hunting on the Arctic ice pack, will find their natural habitat disappearing as the new Amasia supercontinent forms. So when is this catastrophy going to happen? It looks like a new supercontinent forms every 600-800 million years or so, so the polar bears have got some time to change their lifestyle.
Climate change alarmists will say I'm comparing apples to oranges, that the changes due to anthropogenic global warming are going to be sudden, not giving animals like the polar bear a chance to adapt. Maybe. Remember that the change from glacial to interglacial conditions often happens in a few thousand years—about the projected timescale for that dreaded climate change from GHG emissions. Also recall that the polar bear is fully adapted to the current conditions and a change for the warmer or the colder is likely to require further adaptation, but then adaptable species—like bears, rats, cockroaches and humans—are the best survivors.
Indeed, another new paper, this time in Nature Geoscience, reports that the Holocene interglacial will end in 1500 years without those dastardly human CO2 emissions! In “Determining the natural length of the current interglacial,” a team of researchers led by P. C. Tzedakis has concluded that the only thing standing between humanity and a return to ice age conditions may be our profligate use of fossil fuels. Here is that paper's abstract:
No glacial inception is projected to occur at the current atmospheric CO2 concentrations of 390 ppmv. Indeed, model experiments suggest that in the current orbital configuration—which is characterized by a weak minimum in summer insolation—glacial inception would require CO2 concentrations below preindustrial levels of 280 ppmv. However, the precise CO2 threshold as well as the timing of the hypothetical next glaciation remain unclear. Past interglacials can be used to draw analogies with the present, provided their duration is known. Here we propose that the minimum age of a glacial inception is constrained by the onset of bipolar-seesaw climate variability, which requires ice-sheets large enough to produce iceberg discharges that disrupt the ocean circulation. We identify the bipolar seesaw in ice-core and North Atlantic marine records by the appearance of a distinct phasing of interhemispheric climate and hydrographic changes and ice-rafted debris. The glacial inception during Marine Isotope sub-Stage 19c, a close analogue for the present interglacial, occurred near the summer insolation minimum, suggesting that the interglacial was not prolonged by subdued radiative forcing. Assuming that ice growth mainly responds to insolation and CO2 forcing, this analogy suggests that the end of the current interglacial would occur within the next 1500 years, if atmospheric CO2 concentrations did not exceed 240±5 ppmv.
The prediction of the end of the current (Holocene) interglacial in 1500 years is based on paleoclimate information about other glacial and interglacial periods. As the author's state: “The notion that the Holocene (or Marine Isotope Stage 1, MIS1), already 11.6 thousand years (kyr) old, may be drawing to a close has been based on the observation that the duration of recent interglacials was approximately half a precession cycle (~11 kyr).” But there is quite a bit of variation in the characteristics of interglacials past, as can be seen in the illustration below.
Astronomical parameters 100 kyr after present—800 kyr BP and palaeoclimatic records 0–800 kyr BP.
Note that the interglacials are labeled by their associated Marine Isotope Stage and Sub-stage numbers—alternating warm and cool periods in Earth's paleoclimate, deduced from oxygen isotope data. The isotope data, taken from deep sea core samples, are used as proxies reflecting changes in temperature. The authors identify two broad categories of interglacial. Also, two ‘rogue’ interglacials occurred that are not included under the categories identified below:
- (1) MIS5e, MIS7e, MIS9e and MIS19c are characterized by rapid deglaciation, early peaks in Antarctic temperatures and GHG concentrations followed by monotonic declines.
- (2) MIS11c and MIS17 are characterized by protracted deglaciation11, 15 and the persistence of interglacial values over two insolation peaks, with the obliquity maximum post-dating the first precession minimum by 12–13 kyr and preceding the second precession minimum by 8 kyr.
The Holocene shares some characteristics of the first group, but, as the author's point out, the early peaks in Antarctic temperatures and GHG concentrations were not followed by monotonic declines. It has long been accepted that changes in Earth's orbital parameters control the onset of glacials and interglacials (see Chapter 9, “Variations In Earth's Orbit,” in The Resilient Earth for a detailed explanation). The authors provide a fairly good analysis of the various orbital factors during each interglacial but again there is no exact match for the Holocene (MIS1):
In terms of astronomical signature, only MIS11c and MIS19c are comparable to the Holocene as a result of weak eccentricity–precession forcing. MIS11c has traditionally been considered a close astronomical analogue for the Holocene2, but differences in the phasing of precession and obliquity have led to different alignments of the two intervals, with contrasting implications for the natural length of the current interglacial. Alignment ambiguities and differences in deglaciation trajectories, therefore, impose limitations on the MIS1–MIS11c analogy. By contrast, the obliquity maximum occurs very near the precession minimum in both MIS1 and MIS19c, although absolute values of obliquity are different.
While the work identifying similarities between the Holocene and previous interglacials is quite interesting, the paper runs off into the weeds when it starts to claim the next period of glaciation can be, in essence, delayed forever by human CO2 emissions. They do admit that changes in CO2 levels are not the cause of such change. “Climate modelling studies show that a reduction in boreal summer insolation is the primary trigger for glacial inception, with CO2 playing a secondary role,” the authors report.
Unfortunately, they do not stop there. “Lowering CO2 shifts the inception threshold to higher insolation values, but modelling experiments indicate that preindustrial concentrations of 280 ppmv would not be sufficiently low to lead to new ice growth given the subdued insolation minimum.” Again the extremist claim is based not on empirical evidence or direct observation, but on model projections.
While this claim has been made by others, stating that a new glacial onset is impossible without a significant reduction in atmospheric CO2 concentrations is far from proven. The ability of the Earth system to compensate and recover from sharp increases in atmospheric greenhouse gases had been observed many times in the prehistoric past and it is accepted that glaciation has started when CO2 levels were at or above current levels. Just the same, if driving an SUV is keeping the glaciers at bay I say keep on truckin'.
Be safe, enjoy the interglacial and stay skeptical.
If it means putting off the next glacial onset, even polar bears will drive SUVs.