It's the Ocean not the Atmosphere, dummy!

[Anomalism]

How has it been affected?

But it can melt, right? Just like the NH ice melts?

Yes, Antarctica can melt and grow, but it behaves differently.

Northern Hemisphere ice sheets expand and collapse across continents, strongly changing climate and driving glacial cycles. Antarctica is mostly isolated and already ice-covered, so it doesn’t change enough in size to control the timing of ice ages.

 

[ding]

We don’t know precisely, and it likely isn’t imminent on human timescales.

Under natural orbital cycles alone, the next full glaciation would be expected tens of thousands of years from now, because current orbital configuration keeps Northern Hemisphere summer insolation relatively high compared to glacial-start conditions.

That doesn't sound testable. And tens of thousands of years on top of the 11,600 years in this interglacial period is outside of the range of the empirical data.

"...The preceding four interglacial periods are seen at about 125,000, 280,000, 325,000 and 415,000 years before now, with much longer glacial periods in between. All four previous interglacial periods are seen to be warmer than the present. The typical length of a glacial period is about 100,000 years, while an interglacial period typically lasts for about 10-15,000 years. The present inter-glacial period has now lasted about 11,600 years..."

https://www.ssb.no/en/natur-og-milj...594b9225f9d7dc458b0b70a646baec3339/DP1007.pdf

 

[Anomalism]

That doesn't sound testable. And tens of thousands of years on top of the 11,600 years in this interglacial period is outside of the range of the empirical data.

"...The preceding four interglacial periods are seen at about 125,000, 280,000, 325,000 and 415,000 years before now, with much longer glacial periods in between. All four previous interglacial periods are seen to be warmer than the present. The typical length of a glacial period is about 100,000 years, while an interglacial period typically lasts for about 10-15,000 years. The present inter-glacial period has now lasted about 11,600 years..."

https://www.ssb.no/en/natur-og-milj...594b9225f9d7dc458b0b70a646baec3339/DP1007.pdf

Testable here means the theory matches patterns in past data.

It doesn’t mean predicting the exact date of the next glaciation. The “10–15k year interglacial” figure is just an average from past cycles, not a fixed rule, and current conditions also affect the timing.

 

[ding]

Yes, Antarctica can melt and grow, but it behaves differently.

Northern Hemisphere ice sheets expand and collapse across continents, strongly changing climate and driving glacial cycles. Antarctica is mostly isolated and already ice-covered, so it doesn’t change enough in size to control the timing of ice ages.

What data exists that shows Antarctica has been affected by orbital forcing?

 

[ding]

Testable here means the theory matches patterns in past data.

It doesn’t mean predicting the exact date of the next glaciation. The “10–15k year interglacial” figure is just an average from past cycles, not a fixed rule, and current conditions also affect the timing.

Sort of like how physical evidence and D-O events prove the ocean is responsible for abrupt climate changes that can be as abrupt as a few decades?

 

[ding]

because it can grow and collapse and strongly amplify climate change.

Sort of like what would happen if the AMOC collapsed?

 

[ding]

An AMOC shutdown is different. It mainly redistributes existing heat regionally, while orbital changes alter the amount of summer energy reaching high latitudes.

No difference. Both are regional in nature. The same backdrop applies to both. The difference is the speed in which it happens.

 

[ding]

It doesn’t mean predicting the exact date of the next glaciation. The “10–15k year interglacial” figure is just an average from past cycles, not a fixed rule, and current conditions also affect the timing.

Yes, it is empirical data. But according to you, it is cyclical. Regular cycles. So why wouldn't it be somewhat fixed?

 

[Anomalism]

What data exists that shows Antarctica has been affected by orbital forcing?

Antarctic ice cores, ocean sediments, and isotope records show Antarctica responds to orbital cycles, especially obliquity. Researchers see Antarctic temperature and ice-volume changes tracking orbital periodicities like the 41k-year obliquity cycle.

The evidence also shows Antarctica behaves differently from Northern Hemisphere ice sheets. It responds to orbital forcing and ocean changes, yet the large continental ice growth/collapse cycles that dominate glacial pacing are still centered in the Northern Hemisphere.

 

[Anomalism]

Sort of like how physical evidence and D-O events prove the ocean is responsible for abrupt climate changes that can be as abrupt as a few decades?

D-O events are strong evidence that ocean circulation can cause very abrupt regional climate shifts over decades to centuries.

The disagreement is that D-O events occur within glacial periods and don’t by themselves explain the long-term pacing of full glacial–interglacial cycles over 41k/100k year timescales.

 

[Anomalism]

Sort of like what would happen if the AMOC collapsed?

Yes, both involve strong climate feedbacks and can amplify climate change. The difference is that an AMOC collapse mainly redistributes heat regionally and can cause abrupt shifts, while large ice-sheet growth or collapse changes global albedo and affects Earth’s overall energy balance over longer timescales.

 

[Anomalism]

No difference. Both are regional in nature. The same backdrop applies to both. The difference is the speed in which it happens.

Orbital forcing changes the incoming seasonal solar energy at high latitudes, while AMOC changes mostly redistribute heat already inside the climate system. So they’re not identical physically, even if both ultimately influence Arctic ice.

 

[Anomalism]

Yes, it is empirical data. But according to you, it is cyclical. Regular cycles. So why wouldn't it be somewhat fixed?

The cycles are not perfectly periodic like a metronome. Orbital cycles themselves overlap and vary, and the climate response includes nonlinear feedbacks, thresholds, ice-sheet dynamics, and ocean variability.

There is a cyclical structure in the data, but not a fixed rule. That’s why glacial periods and interglacials vary in length even within the same overall orbital framework.

 

[ding]

Antarctic ice cores, ocean sediments, and isotope records show Antarctica responds to orbital cycles, especially obliquity. Researchers see Antarctic temperature and ice-volume changes tracking orbital periodicities like the 41k-year obliquity cycle.

The evidence also shows Antarctica behaves differently from Northern Hemisphere ice sheets. It responds to orbital forcing and ocean changes, yet the large continental ice growth/collapse cycles that dominate glacial pacing are still centered in the Northern Hemisphere.

So if I understand you correctly, OF triggers glacial and interglacial cycles in the NH. Is it the same in the SH? When you say responds, what does that mean exactly?

And why is the NH on 100k cycle and the SH is 41k cycle?

 

[ding]

D-O events are strong evidence that ocean circulation can cause very abrupt regional climate shifts over decades to centuries.

The disagreement is that D-O events occur within glacial periods and don’t by themselves explain the long-term pacing of full glacial–interglacial cycles over 41k/100k year timescales.

We already covered this. Abrupt climate changes are not limited to glacial periods. And as far as the 41k/100k timescales that's not compelling evidence since the timescales changed in the NH and apparently not in the SH.

 

[ding]

Yes, both involve strong climate feedbacks and can amplify climate change. The difference is that an AMOC collapse mainly redistributes heat regionally

If the total solar energy only changes globally by a tiny amount, it's no different.

and can cause abrupt shifts, while large ice-sheet growth or collapse changes global albedo and affects Earth’s overall energy balance over longer timescales.

Unless of course the collapse of the AMOC leads to large ice-sheet growth because of feedback, then it is the same.

 

[ding]

even if both ultimately influence Arctic ice.

That was my point.

 

[Anomalism]

So if I understand you correctly, OF triggers glacial and interglacial cycles in the NH. Is it the same in the SH? When you say responds, what does that mean exactly?

And why is the NH on 100k cycle and the SH is 41k cycle?

“Responds” means Antarctica’s temperature, ice, and surrounding ocean conditions shift in step with orbital changes, but without driving global ice age timing. It follows orbital cycles mainly through changes in seasonal sunlight and ocean heat, especially the 41,000 year tilt cycle.

The northern hemisphere behaves differently because it has large continental ice sheets that can grow and collapse dramatically. That amplifies climate changes and produces the dominant 100,000 year glacial cycles, while Antarctica’s more stable, ocean isolated ice sheet mostly mirrors the orbital forcing rather than pacing it.

 

[Anomalism]

We already covered this. Abrupt climate changes are not limited to glacial periods. And as far as the 41k/100k timescales that's not compelling evidence since the timescales changed in the NH and apparently not in the SH.

D-O events show that ocean circulation can flip climate state quickly, but they don’t match the global ice age pacing. They are mainly North Atlantic/Northern Hemisphere features riding on top of a larger glacial background, not the mechanism that sets when full glacial–interglacial transitions start and end.

The 41k vs 100k shift isn’t explained by hemispheres having different cycles. It reflects a change in how the whole Earth system responds to orbital forcing. Antarctica still follows the 41k obliquity signal, but it doesn’t generate the global ice volume swings that define the 100k cycle because it lacks large, variable land ice.

 

[Anomalism]

If the total solar energy only changes globally by a tiny amount, it's no different.

Unless of course the collapse of the AMOC leads to large ice-sheet growth because of feedback, then it is the same.

Yes, AMOC changes can contribute to cooling that supports ice sheet growth, and ice sheet growth then changes albedo and amplifies global cooling. They are linked in a feedback chain.

But they are not the same mechanism. AMOC is an internal heat redistribution process, while ice sheet change affects the planet’s overall energy balance over long timescales. The key question is what sets the slow pacing of those transitions over tens of thousands of years.