Is the slowing of oceanic turnover contributing to Halocene warming?

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Discussion Overview

The discussion revolves around the potential causes of Holocene warming over the last 15,000 years, with a focus on the role of oceanic turnover and its interaction with atmospheric temperature changes. Participants explore various factors, including Milankovitch cycles and greenhouse gas concentrations, while questioning the significance of ocean heat dynamics in relation to observed warming trends.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest that Milankovitch forcing, particularly the 20,000-year precession effect, may have contributed to Holocene warming.
  • Others argue that increases in greenhouse gases, specifically CO2 and methane, are significant factors in the warming, though the exact contribution of each factor remains unclear.
  • A participant raises the possibility that reduced vertical turnover in the upper ocean layers over the past 15,000 years could have led to increased surface warming, potentially having a greater impact on atmospheric warming than the increase in CO2 levels alone.
  • Another participant notes that while ocean temperature measurements indicate warming, there is no clear consensus on whether the rate of vertical turnover in the oceans is slowing down, which could influence atmospheric temperature changes.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the causes of Holocene warming, with no consensus on the relative contributions of oceanic turnover, greenhouse gas increases, or Milankovitch cycles.

Contextual Notes

Limitations in the discussion include uncertainties about the exact mechanisms of oceanic heat dynamics, the dependence on specific definitions of turnover rates, and unresolved questions regarding the contributions of various factors to warming.

zankaon
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What might be underlying possible causes(s) of Halocene warming over last 15000 years? Any mild Milankovitch forcing by just 20k precession effect? http://en.wikipedia.org/wiki/Milankovitch_Forcing"
 
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Besides differances in Earth's orbit that caused the perihelion to occur closer in time to the NH summer, there were substantial increases in greenhouse gases (CO2 and Methane).

Hard to say offhand how much each of these contributed (percentage wise) to the warming, but they are all factors.
 


The top 2.5-3.5 meters of ocean heat capacity is ~ equal to that of atmosphere; see Ocean Heat Storage thread. Since the LGM 20,000 years ago, and over Holocene of ~15,000 years, one has had gradual overall warming of atmosphere (ice core gases?) and supposedly of average ocean temperature. Might upper layer of ocean, for over 15,000 years, perhaps statistically have had less vertical turnover, leading to gradual increased surface warming, and secondary atmosphere warming? Might any such background primary warming of ocean upper layer have had much more of an effect on atmospheric warming and observed consequences, than just increase in CO2 (just 280 -> ~385 ppm for last ~200 yrs)? Thus is the paradox of just ~35% increase in CO2, compared to observed apparent greater consequences, related more initially to oceanic heat dynamics?
 
Highly accurate temperature measurements of the ocean have been made for about 50 years.
These are measurement that extend to great depths (using buoys and other devices).
From these measurements, it has become clear that the oceans are warming.
So, heat has been flowing from the atmosphere into the oceans.

The rate of vertical turnover in oceans is another matter. As far as I know, there is not a clear conclusion as to wether the turnover is slowing down or not. If it does slow down, then the atmosphere would warm faster than it has been.
 

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