Friday 9 June 2023

Chautauqua 2.

I had the following chat with GPT4, using the Chat With PDF plugin. GPT4 was able to use that plugin and carry out analysis of the implications of the paper concerned. 


I want to talk about


Used ChatWithPDF [this is where it accesses the web link to the PDF file and (presumably) loads the paper into a vector database.]

Great, I've successfully loaded the PDF. What would you like to discuss or know about this document?


Can you summarise the paper in a paragraph?


Used ChatWithPDF 

The paper titled "A Mechanism for the High Rate of Sea Ice Thinning in the Arctic Ocean" by Bitz and Roe (2004) discusses the spatial distribution of sea ice thinning over the past few decades in the central Arctic. The authors present a mechanism based on the thermodynamics of sea ice to explain how sea ice can thin most where the ice was initially thickest. They also develop a general theory, which accounts for ice dynamics as well as thermodynamics, to describe the equilibrium thickness sensitivity of sea ice to changes in forcing. The study uses simple models to investigate this mechanism and compares the theoretical estimates to results from a simple zonal-mean energy balance model and the Coupled Model Intercomparison Project (CMIP) models. The results suggest that when a climate perturbation causes the ice to thin, the greatest thinning occurs in the central Arctic, where the ice is thickest, and less thinning occurs in the subpolar seas.


What role do the different time behaviours of first-year and multi-year sea ice play in the observed thinning of thick sea ice?


Used ChatWithPDF

The paper explains that the thinning of sea ice is a function of its initial thickness due to the inherent thermodynamics of sea ice. When a climate perturbation causes the ice to thin, the greatest thinning occurs where the ice is initially thickest. This is because sea ice returns to its equilibrium thickness by adjusting its growth rate, a process that is faster for thinner ice. Thinner ice doesn't need to thin much to increase its growth rate significantly, thereby establishing a new equilibrium with relatively little change in thickness. In contrast, thicker ice must thin much more. This growth-thickness feedback is the key to explaining the high rate of thinning in the central Arctic compared to thinner ice in the subpolar seas. The paper also discusses the role of ice dynamics and how they can influence the thickness change.


Armour et al 2010 observe that:

Given the strong thickness–growth feedback of sea ice (Bitz and Roe 2004), where in a warming climate we can expect the thicker MY (multi year) ice to thin at a greater rate than the thinner FY (first year) ice, and the fact that the ratio of MY to FY ice entering into the MY ice category each year is decreasing, it is likely that the difference between FY and MY ice survival ratios will decrease in a warming climate. If this occurs, the Arctic sea ice system would move toward a regime of decreased memory and decreased sensitivity to climate forcing.

What can you say about the concept of memory in two states of Arctic sea-ice 1) an ice pack dominated by thick multi-year sea ice. 2) an ice pack dominated by mainly first-year ice?


The concept of "memory" in the context of Arctic sea-ice refers to the persistence of sea ice conditions from one year to the next.

In an ice pack dominated by thick multi-year sea ice, the memory is high. This is because multi-year ice, being thicker, survives the summer melt season and carries information about past climate conditions into the next year. The thickness of this ice also means it has a slower response time to changes in climate conditions, which contributes to its high memory. This persistence of conditions can lead to a higher sensitivity to long-term climate forcing, as changes can accumulate over time.

In contrast, an ice pack dominated by mainly first-year ice has a lower memory. First-year ice is thinner and more likely to melt completely during the summer, meaning it doesn't carry as much information about past climate conditions into the next year. This ice also has a faster response time to changes in climate conditions, which contributes to its lower memory. The dominance of first-year ice means that the ice pack's state is more influenced by the conditions of the current year, and less by the history of past conditions. As a result, the sensitivity to climate forcing is decreased, as changes don't accumulate as much over time.

In a warming climate, as the Arctic sea ice system transitions from being dominated by multi-year ice to first-year ice, we can expect a decrease in memory and sensitivity to climate forcing. This is because the thinner first-year ice is less likely to survive the summer melt season, and the ice pack's state becomes more dependent on the conditions of the current year.


The available satellite record contains data of sea ice extent and concentration from 1979 to the current day. It shows a non linear decline in extent of three phases. The PIOMAS model uses atmospheric and ocean data to model the sea ice thickness in a gridded dataset. Given the findings of Bitz & Roe 2004, and the above comments of Armour et al... Can you propose how sea-ice might have declined in terms of extent, volume and thickness over the available satellite period. Can you also suggest why there might be three phases?


Given the findings of Bitz & Roe (2004) and the comments of Armour et al., we can infer that the decline in Arctic sea ice over the available satellite period has likely been characterized by changes in extent, volume, and thickness, with these changes being influenced by the balance between multi-year (MY) and first-year (FY) ice.

Extent: The satellite record shows a non-linear decline in sea ice extent. This decline is likely due to a combination of increased melting due to warming temperatures and changes in atmospheric and oceanic circulation patterns. The decline in extent is likely more pronounced during the summer melt season, when thinner FY ice is more susceptible to melting.

Volume and Thickness: The PIOMAS model, which incorporates atmospheric and ocean data, can provide insights into changes in sea ice volume and thickness. Given the strong thickness-growth feedback identified by Bitz & Roe (2004), we can expect that thicker MY ice has been thinning at a greater rate than thinner FY ice. This would result in a decrease in overall sea ice volume. Additionally, as the proportion of MY ice decreases and FY ice increases, the average thickness of the ice pack would also decrease.

As for the three phases of sea ice decline, these could potentially be explained by different dominant processes or changes in external forcing.

The first phase might be characterized by a balance of MY and FY ice, with the system still having a high memory and sensitivity to climate forcing.

The second phase could represent a transition period, where warming temperatures and changing circulation patterns lead to a decrease in MY ice and an increase in FY ice. This would result in a faster rate of decline in sea ice extent and volume.

The third phase might be a new regime dominated by FY ice, with lower memory and sensitivity to climate forcing. In this phase, the decline in sea ice extent and volume might be slower than in the second phase, but the overall state of the ice pack would be more susceptible to interannual variability and less influenced by long-term trends.

This is a simplified interpretation and actual processes could be more complex, involving other factors such as changes in snow cover, ocean heat content, and feedback mechanisms like the ice-albedo feedback.


Your final three points are close. As the volume declined what impact would it have on ice albedo feedback? And with this in mind which of the three phases do you consider would show the greatest rate of decline of volume and September extent of Arctic sea ice?


The ice-albedo feedback is a key factor in the melting of Arctic sea ice. When sea ice melts, it exposes the darker ocean surface, which absorbs more solar radiation than the reflective ice. This additional absorbed heat causes further melting, leading to more open water, and thus creating a positive feedback loop. As the volume of sea ice declines, this feedback mechanism becomes more pronounced, accelerating the rate of ice melt and warming of the Arctic.

As for the three phases of sea ice decline:

In the first phase, where the ice pack is dominated by multi-year ice, the decline in volume and September extent would likely be slower. This is because multi-year ice is thicker and more resilient to melting.

The second phase, the transition period, would likely show the greatest rate of decline in both volume and September extent. This is due to the increasing dominance of first-year ice, which is thinner and more prone to melting. The ice-albedo feedback would be particularly strong in this phase, as the melting of first-year ice exposes more dark ocean surface, absorbing more solar radiation and leading to further melting.

In the third phase, where the ice pack is dominated by first-year ice, the rate of decline might slow down compared to the second phase. This is because the ice pack has already transitioned to a state that is more influenced by interannual variability and less by long-term trends. However, the ice-albedo feedback would still be significant in this phase, as the predominantly first-year ice continues to be susceptible to melting, exposing more ocean surface and absorbing more solar radiation.


Excellent, very well done.


Thank you! I'm glad I could help. If you have any more questions about this topic or anything else, feel free to ask!

So, in this exchange we saw GPT4 able to upload a complex scientific paper and correctly respond to questions all within one session of discussion. In essence it drums home how stupid I was when I first read Bitz and Roe 2004 many years ago. In the intervening decades since publication of that paper, I have come to the conclusion that this paper was pivotal as it held within it the implications that would have enabled me to predict the actual progression of events up to the most recent post-2007 period, had I been intelligent enough to see these implications. 

Granted the 'understanding' of the thing that is GPT4, as evidenced above, was guided by my questioning. For example, my asking about three phases. Nonetheless, it was able to fill in the gaps and produce a framework of understanding, bearing in mind that this is not like human understanding. Nonetheless, I have had several interesting interactions with GPT4 and scientific papers, even giving it papers to read followed by questioning from myself with me only reading the paper afterwards.

This trick of 'reading' papers is (as you'd expect) not like a human reading a paper. For a human we need to build a conceptual framework in order to reach comprehension, it might take me many hours (sometimes days or more) to properly read and comprehend a paper in a branch of science with which I've had no prior engagement. What GPT4 is doing is different, from what I can work out, it seems to be converting the paper to a tokenised text version in a vector database.

But learning by conversing is a more fluid way to develop an understanding, I have better recollection of one conversation than with one reading of a dry technical paper. I should here note that it probably isn't capable of handling graphical results or complex equations. But reading the paper, then uploading to GPT4 and discussing seems to me a potentially productive use of the Intelligence.

For what it's worth, calling these Artificial Intelligences is unhelpful. They are best described as non-human intelligences, but why complicate matters by creating my own obscure terminology?

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