It's the Ocean not the Atmosphere, dummy!

[EMH]

Loss of heat circulation from the Atlantic to the Arctic.

and your evidence that this has ever happened is.... you have none, you just pulled it out of your taxpayer funded CO2 FRAUD "faux skeptic" ass. Indeed, the last ocean current chart you posted had warm water off Greenland and cold water off Alaska, yet Greenland is in ice age and Alaska is not = you refuted yourself with your own chart.

orbital forcing

is another phrase for Milankovich aka McBullshit, already refuted on USMB on both poles





What the ice cores prove is that continent specific ice ages on Greenland and Antarctica grow new ice layers every year, and pay no attention to ocean currents or CO2 levels....

 

[Mushroom]

Yes, plate tectonics led to each pole becoming thermally isolated from warm marine currents.

But more importantly, the cutting off of the current between the Atlantic and Pacific. Antarctica started to cool down about 25 mya, and became ice covered around 14 mya. That took around 6-8 million years to move from a tropical environment to something resembling Alaska or Siberia today. And it remained that way for millions of years more, only finally resembling what is there today over huge period of time.

But it was cutting off the current through what is now Panama that threw the entire planet into a deep freeze. Prior to that, even Alaska more closely resembled modern Florida than what is seen there today.

 

[Anomalism]

We don't know that.

We know enough to say that abrupt ocean circulation shifts alone have not been shown to reproduce the full long term glacial cycle structure across repeated cycles. That’s different from claiming we have the entire system solved.

The reason orbital forcing remains central is not because the record looks like perfect clockwork, but because the timing still aligns with orbital periodicities far more consistently than any demonstrated purely internal ocean cycle mechanism has so far.

 

[Mushroom]

I understand all that. NH dominates the climate of the planet for good reasons. That's not what I was asking though.

This should be obvious to anybody that actually has a working brain. All one has to do is look at a map.

In short, it's all about geography.

The Northern Hemisphere is dominated by 4 large land masses that separate two large bodies of water. And those two large bodies of water make up 60% of the area.

Then move to the Southern Hemisphere. Three much smaller land masses, separated by three large bodies of water. Where water makes up over 80% of the area.

Here is the thing about glaciation and ice sheets, they do not happen over water. They can extend into the water, but the actual glaciation occurs on land. Ergo, with less land there is less glaciation.

Here, let me throw up another map, this should make it even more clear.

Now the Tropics of Cancer and Capricorn are the points of latitude where on the solstice the sun is either directly overhead or at 90 degrees as solar midnight. Now notice the huge difference in climates when one moves north or south of those lines.

In the Northern Hemisphere, glaciation happened north of the Tropic of Cancer. In the Southern Hemisphere it happened south of the Tropic of Capricorn. Between the two, outside of extremely high altitudes there was no glaciation. So when discussing glacial cycles, it is much more important to discuss land and water areas above and below those two points.

The largest known glacial cycles in the Sothern Hemisphere are those of Patagonia.

They ebbed and flowed just like those in Europe and North America. But of course grew nowhere near as large because the land mass was tiny compared to North America and Eurasia. But they were real, if less well known.

I*n fact, if Magellan had tried to travel from the Atlantic to the Pacific roughly a century earlier, he never would have discovered the Straight that bears his name. The ice sheet expanded so much during the Little Ice Age that even 50 years earlier it was a seasonal passage at best.

Any time somebody tries to claim that the Little Ice Age was a "regional event", I know they are an idiot. Of course, this is nothing new for me. I admit I did not know about this until my wife's uncle told me about the Patagonia Glaciation in 1984. He was a paleontologist and most of his discoveries were in those areas of Patagonia. Much like in Canada and North America, the effects on the underlying rock was excellent in exposing fossils.

 

[Anomalism]

Higher solar radiation in one part of the year due to tilt, or obliquity, means less solar radiation in the “opposite” part of the year.

Globally and annually the net energy change from orbital forcing is small. The importance of Milankovitch forcing is that it redistributes sunlight seasonally and latitudinally, especially at high northern latitudes where ice sheet stability is extremely sensitive to summer melt conditions.

That’s why the theory focuses so heavily on Northern Hemisphere summer insolation rather than global annual average energy. A few weak summers in the right regions, sustained over long periods, can allow persistent snow accumulation and ice sheet growth even without a large change in total planetary energy input.

 

[Anomalism]

I understand all that. NH dominates the climate of the planet for good reasons. That's not what I was asking though.

Wouldn't that response be out of step with the northern hemisphere's response? Is that seen?

Not out of step in a simple sense, but yes, differences in timing between hemispheres are observed. Antarctic records sometimes lead or lag depending on the interval and proxy. That’s one reason scientists talk about coupled ocean atmosphere dynamics and the bipolar seesaw rather than a perfectly synchronized global response. The hemispheres are linked, but they do not always evolve in lockstep on all timescales.

 

[otto105]

The role of the ocean in storing, distributing and establishing climate is well known and well understood. Change the currents and you change the climate. Some regions are more sensitive to change than others and have more of a global impact than others. The Arctic is that region. The Little Ice age was triggered by a disruption of the ocean's heat circulation to the Arctic and that when that heat circulation was restored, the planet returned to it's natural interglacial warming trend. The contribution of the Industrial Revolution isn't nothing but all warming is not due to it. 0.22C top 0.5C is the contribution of 120 ppm of CO2.

1. The ocean stores the majority of heat the earth receives from the sun
2. The ocean holds 1000 times more heat than the atmosphere
3. The ocean distributes that heat to the rest of the globe using currents
4. Without ocean currents the polar regions would be colder and the equator would be hotter such that much of the planet would be inhospitable for life
5. Ocean currents are affected by density (salinity and thermal expansion) and wind.
6. Wind patterns are affected by the sun
7. If heat circulation from the Atlantic to the Arctic were disrupted it would lead to catastrophic cooling

The following are excerpts from papers explaining the science behind the climate changes of the past 3 million years.

It is found that the global salinity variations associated with the thermohaline circulation may have a tendency to make the circulation increasingly asymmetric with respect to the equator. As a consequence the salinity difference between the Pacific and the Atlantic Ocean may be slowly increasing. Such a process could have a time scale long enough to be comparable with the time span between major glaciations. A speculative glaciation cycle is proposed which involves the above mentioned property of the thermohaline circulation. In this cycle the role of a Northern Hemisphere glaciation is to bring excess freshwater from the Pacific to the Atlantic.

https://www.sciencedirect.com/science/article/abs/pii/S0031018285800201

Atlantic Ocean Circulation During the Last Ice Age​

There is strong evidence that the circulation of the deep Atlantic during the peak of the last Ice Age, or the Last Glacial Maximum (LGM; ~22,000 to 19,000 years ago) was different from the modern circulation (Boyle & Keigwin 1987, Duplessy et al. 1988, Marchal & Curry 2008). Compilations of deepwater δ13C and CdW for the LGM (Figure 5) show several features that contrast with their modern distributions. Whereas much of the modern deep western Atlantic has similar δ13C values because it is filled with NADW, during the LGM, the range of δ13C values was larger than today, with higher values in NADW and lower values in AABW. The main core of high-δ13C, low-CdW NADW was at least 1000 meters shallower than today, probably because the density difference between surface waters and deep water was reduced — surface salinity may have decreased as a result of less evaporation due to colder glacial temperatures, and as a result of input of freshwater from glaciers surrounding the North Atlantic (Boyle & Keigwin 1987). In the western Atlantic, depths below ~2 km were filled with AABW. Radiocarbon data suggest that deepwater was older (Keigwin & Schlegel 2002), consistent with less NADW and more AABW as indicated by the δ13C and CdW of benthic foraminifera. Glacial δ13C data from the eastern Atlantic suggest that the boundary between glacial AABW and glacial NADW may have been shallower than in the western Atlantic (Sarnthein et al. 1994), although the difference may be the result of local effects caused by increased glacial productivity and higher rates of remineralization of low-δ13C organic carbon in the eastern basin. Inferences using other kinds of proxy data of deep Atlantic circulation are consistent with the changes inferred from δ13C, Cd/Ca and 14C of benthic foraminifera (Lynch-Steiglitz et al. 2007).

Deep Atlantic Circulation During the Last Glacial Maximum and Deglaciation​

As shown by the work of Dansgaard and his colleagues, climate oscillations of one or so millennia duration punctuate much of glacial section of the Greenland ice cores. These oscillations are characterized by 5°C air temperature changes, severalfold dust content changes and 50 ppm CO2 changes. Both the temperature and CO2 change are best explained by changes in the mode of operation of the ocean. In this paper we provide evidence which suggests that oscillations in surface water conditions of similar duration are present in the record from a deep sea core at 50°N. Based on this finding, we suggest that the Greenland climate changes are driven by oscillations in the salinity of the Atlantic Ocean which modulate the strength of the Atlantic's conveyor circulation.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/PA005i004p00469

Water Masses in the Deep Atlantic Ocean​

The Atlantic Ocean is the only ocean basin that features the transformation of surface-to-deepwater near both poles. Warm salty tropical surface waters flowing northward in the western Atlantic cool in transit to and within the high-latitude North Atlantic, releasing heat to the overlying atmosphere and increasing seawater density. Once dense enough, these waters sink and flow southward between ~ 1000 and 4000m. This North Atlantic Deep Water (NADW), as it is called, flows from the Atlantic to the Southern Ocean where much of it upwells — or rises to the surface — around Antarctica, and some of it circulates Antarctica before entering the rest of the world's deep oceans. Antarctic Bottom Water (AABW), which is formed close to Antarctica, is denser than NADW, and flows northward in the Atlantic below NADW. AABW is confined to water depths below 4000 meters in the tropical and North Atlantic. Antarctic Intermediate Water (AAIW) flows northward above NADW. The presence of these three water masses in the Atlantic Ocean is evident in cross-sections of many water properties, including salinity, phosphate concentration and carbon isotope ratios (Figure 2). The residence time of deepwater in the western Atlantic is approximately 100 years (Broecker 1979), meaning that the average water parcel spends about a century in the deep Atlantic.

Why is Deep Water Formed in the Atlantic and not the Pacific?​

Warren (1983) first noted that the difference in salinity between the North Pacific and the North Atlantic (Figure 1) was the principal reason deep water formation occurs today only in the North Atlantic. Salty water, when cooled, achieves a higher density and is thus able to sink to greater depth in the water column. Wintertime cooling occurs in both the North Atlantic and North Pacific, but since the surface waters of the North Atlantic are much closer in salinity to the mean of the ocean's deep water, they achieve a density high enough to sink to great water depths. Warren (1983) noted that the salinity of the North Pacific was low because of relatively low evaporation, little exchange with salty tropical waters, and an influx of fresh water from precipitation and river runoff. Emile-Geay et al.(2003) reevaluated the Warren (1983) results and fundamentally confirmed his thesis, noting that atmospheric moisture transport from the Asian monsoon was also an important source of fresh water to the North Pacific not originally considered by Warren. Interestingly, Warren also noted that the North Atlantic had much greater river runoff than the North Pacific, so its higher surface salinities must be the result of greater evaporation in the Atlantic basin.

Broecker et al. (1990a) noted that higher Atlantic salinities are the result of a net transfer of water vapor from the Atlantic to the Pacific over the Isthmus of Panama, equivalent to approximately 0.35 Sverdrup (106 m3 per second). In the absence of other processes, this would raise the salinity of the Atlantic by about 1 salinity unit each 1000 years. If the Atlantic salinity is in balance, then it must be exporting the excess salt (enough to compensate for the lost fresh water) through ocean circulation processes. Today this is occurring through the production and export of North Atlantic Deep Water.
At times in the past, rapid melting of ice sheets surrounding the North Atlantic was great enough to alter surface salinities, likely reducing the density of deep water formed, and slowing the export of deep water from the North Atlantic. Broecker et al. (1990b) hypothesized that natural oscillations in the rate of water vapor exchange between the Atlantic and the Pacific during the last glacial period were responsible for the rapid, short term fluctuation ocean circulation linked to the abrupt millennial-scale Dansgaard-Oeschger Events seen in the Greenland ice cores (Figure 9).

Deep Atlantic Circulation During the Last Glacial Maximum and Deglaciation​

What Replaces the Deep Water that Leaves the Atlantic?​

There are three main pathways for water to return to the North Atlantic and renew NADW, a warm-water route and two cold water routes (Figure 3). The "warm-water route" begins with the flow of surface and thermocline water from the Pacific to the Indian Ocean through the Indonesian Seas. Both colder return flows involve Antarctic Intermediate Water (AAIW), described above. AAIW enters the southern South Atlantic through the Drake Passage between Antarctica and South America, with some flowing into the Atlantic and some flowing into the Indian Ocean. AAIW also enters the Indian Ocean from south of Tasmania and flows westward towards Africa, where it joins the warm-water flow and the other branch of AAIW before rounding southern Africa, entering the South Atlantic, and flowing northward (Gordon 1985, Speich et al. 2002). Along its transit to the North Atlantic, AAIW from the Drake Passage, flowing above Tasman AAIW, mixes with overlying water and contributes to the "warm-water route" (Gordon 1986). These return flows provide a significant source of heat to high northern latitudes. Together, southward flow of water in the deep Atlantic and its shallower return flows are a large component of what is known as the global Meridional Overturning Circulation (MOC).

Deep Atlantic Circulation During the Last Glacial Maximum and Deglaciation​

Hilarious climate toddler.

 

[Anomalism]

I wasn't arguing the initiating mechanism is irrelevant. You keep arguing timescales but the timescales changed.

The fact that the dominant pacing shifted from 41k to 100k without a corresponding change in the orbital frequencies is why scientists invoke nonlinear threshold behavior and internal feedbacks. The system changed how it responded to orbital forcing.

 

[EMH]

Not out of step in a simple sense, but yes, differences in timing between hemispheres are observed. Antarctic records sometimes lead or lag depending on the interval and proxy. That’s one reason scientists talk about coupled ocean atmosphere dynamics and the bipolar seesaw rather than a perfectly synchronized global response. The hemispheres are linked, but they do not always evolve in lockstep on all timescales.

100% refuted by the documented truth that during the past million years Greenland froze while North America thawed at the same time.

 

[Anomalism]

100% refuted by the documented truth that during the past million years Greenland froze while North America thawed at the same time.

I don't think anybody is interested in your perspective.

 

[EMH]

^^^^^

LOL!!!