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Ch. 11: The secret life of chimneys
https://www.booktalk.org/ch-11-the-secret-life-of-chimneys-t31147.html
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Author:  Chris OConnor [ Tue Jun 16, 2020 6:35 pm ]
Post subject:  Ch. 11: The secret life of chimneys

A Farewell to Ice: A Report from the Arctic
by Peter Wadhams


Please use this thread to discuss Ch. 11: The secret life of chimneys.

Author:  Robert Tulip [ Wed Oct 14, 2020 4:11 am ]
Post subject:  Re: Ch. 11: The secret life of chimneys

Chapter 11: The Secret Life of Chimneys
Ocean chimneys are deep rotating cylinders of water that sink cold water from the surface to the deep, in places such as the Greenland Sea. Cold salty water from the poles sinks and draws in warmer surface water from lower latitudes. The Great Ocean Conveyor Belt then takes about 1000 years to transport water all the way around the planet, connecting all the seas and currents.

There are many maps of this process, formally called the Global Thermohaline Circulation. My favourite maps of the world from the South and North are from https://rightbasicbuilding.com/earth-oc ... lar-views/ with the poles at the centre, a very different planetary framework.

The sinking water in the Greenland Sea is connected to the Gulf Stream which keeps Europe warmer. A gyre spins the water in a big circular current. In the nearby Denmark Strait between Greenland and Iceland, the world’s biggest waterfall is at the boundary of the Arctic and Atlantic oceans, tipping cold water over a cataract that is about three miles deep.

This chapter only tangentially discusses climate change in its first sections, noting that warming has disrupted the currents, and telling the story of the scientific research to discover them. It turns out these chimneys are very fragile, and sea ice melt is destroying them. They used to last for years without moving, far longer than most eddies. But the lack of research means that scientists now don’t know if these vital channels in the global ocean system are collapsing.

Ocean current disruption was the theme of the 2004 cli-fi movie The Day After Tomorrow, which Wadhams says was “dramatically inaccurate”. Nonetheless, the risk of failure of the Atlantic Meridional Ocean Current may well be real.

A recent open access scientific review at https://agupubs.onlinelibrary.wiley.com ... 19JC015083 provides the following: “models across the full spectrum of complexity have identified the concerning possibility that the AMOC could be prone to collapse. The basic idea is that the salt‐advection feedback that currently maintains a strong AMOC can also work against it: a weakened AMOC would transport less salt into the subpolar North Atlantic, leading to reduced convection and even more weakening of the AMOC. A state would result in which no NADW is formed, and the deep Atlantic is either stagnant or experiences basinwide upwelling of abyssal waters formed around Antarctica. An AMOC collapse would have global consequences and could lead to reduction in surface air temperatures of up to 10 °C in the North Atlantic (Barreiro et al., 2008; Jackson et al., 2015; Liu et al., 2017; Manabe & Stouffer, 1988; Vellinga & Wood, 2002). Evidence of temperature change of this magnitude has been identified in paleo‐proxy records (Blunier & Brook, 2001; de Abreu et al., 2003; Dansgaard et al., 1993), giving credence to the hypothesis that AMOC collapse events were responsible for rapid climate change during the Pleistocene era of ice ages (Broecker et al., 1990). The Fifth Assessment Report of the Intergovernmental Panel on Climate Change identifies an AMOC collapse as one of the tipping points in the climate system (Collins et al., 2013), with a low probability of occurrence but potentially with a high impact.”

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