Re: Gulf Stream's fate to be decided by climate 'tug-of-war'

[John Nissen]

Hi Renaud,

Cripes!!  Refreezing the Arctic could not be more urgent!

When I looked into the scientific paper [1] on which your article was based, it has frightening evidence that we could be near a Heinrich event, because we already have so much meltwater from Greenland and that could be a prelude to the collapse of glaciers to start an event: with avalanches of ice blocks cascading into the sea, floating some distance and depositing "ice rafted debris" (IRD - the main evidence for a Heinrich event).  This would be sufficient to divert the Gulf Stream water into a more southerly route and change climates in many regions.  Albert has evidence that such a collapse occurred in the past, leading to the "great flood" whose story is in many peoples' prehistory handed down orally from generation to generation.

BTW, Albert has a theory about the dating of this collapse: that carbon dating would overestimate the time before present.  There was definitely some kind of huge ice collapse and sea level rise, which is conventionally dated to 8.2 kya (thousand years before present) but might be much sooner according to Albert.  There have also been smaller IRD events called Bond cycles, with surprising regularity suggesting some external driving, e.g. by the moon producing exceptional tides which lifted glacier terminations higher than usual.

John

[1] Zhou et al. (Science, May 2024)

Heinrich event ice discharge and the fate of the Atlantic Meridional Overturning Circulation

https://www.science.org/doi/10.1126/science.adh8369

 

Editor’s summary

Will ice mass loss from the Greenland Ice Sheet caused by climate warming disrupt large-scale ocean circulation? Zhou et al. reconstructed iceberg production rates during the massive calving episodes of the last glacial period, called Heinrich events, when icebergs did affect ocean circulation. The authors found that present-day Greenland Ice Sheet calving rates are as high as during some of those events. However, because melting is causing the Greenland Ice Sheet to recede from the coasts of Greenland, where icebergs originate, its iceberg discharge should not persist long enough to cause major disruption of the Atlantic overturning circulation by itself. —Jesse Smith

 

Abstract

During Heinrich events, great armadas of icebergs episodically flooded the North Atlantic Ocean and weakened overturning circulation. The ice discharges of these episodes constrain the sensitivity of overturning circulation to iceberg melting. We reconstructed these ice discharges to be as high as 0.13 Sverdrup (Sv) (1 Sv = 1 million cubic meters per second) during Heinrich event 4 and to average 0.029 Sv over all episodes. The present-day Greenland Ice Sheet calving of icebergs is comparable to that of a mid-range Heinrich event. As the future Greenland Ice Sheet recedes from marine-terminating outlets, its iceberg calving likely will not persist long enough for icebergs alone to cause catastrophic disruption to the Atlantic overturning circulation, although the accelerating Greenland runoff and continued global warming remain threats to the circulation stability.

 

On Sat, Jun 22, 2024 at 7:24 PM Renaud de RICHTER <renaud.d...@gmail.com> wrote:

https://www.livescience.com/planet-earth/climate-change/gulf-streams-fate-to-be-decided-by-climate-tug-of-war