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Messages - Mozi

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The linked reference provides new insights on how the subpolar gyre can contribute to abrupt climate change:

Camille Li, Andreas Born: Coupled atmosphere-ice-ocean dynamics in Dansgaard-Oeschger events, Quaternary Science Reviews, Volume 203, 2019,Pages 1-20,ISSN 0277-3791, doi.org/10.1016/j.quascirev.2018.10.031.

https://www.sciencedirect.com/science/article/pii/S0277379118305705?via%3Dihub

Abstract: "The Dansgaard-Oeschger events of the last ice age are among the best studied abrupt climate changes, yet a comprehensive explanation is still lacking. They are most pronounced in the North Atlantic, where they manifest as large temperature swings, on timescales of decades or shorter, between persistent cold (stadial) and warm (interstadial) conditions. This review examines evidence that Dansgaard-Oeschger events are an unforced or “spontaneous” oscillation of the coupled atmosphere-ice-ocean system comprising the North Atlantic, Nordic Seas and Arctic, collectively termed the Northern Seas. Insights from reanalysis data, climate model simulations, and idealized box model experiments point to the subpolar gyre as a key coupling region where vigorous wind systems encounter the southernmost extension of sea ice and the most variable currents of the North Atlantic, with connections to the deep ocean via convection. We argue that, under special conditions, these components can interact to produce Dansgaard-Oeschger events. Finding the sweet spot is a matter of understanding when the subpolar region enters a feedback loop whereby changes in wind forcing, sea ice cover, and ocean circulation amplify and sustain perturbations towards cold (ice-covered) or warm (ice-free) conditions. The resulting Dansgaard-Oeschger-like variability is seen in a handful of model simulations, including some “ugly duckling” pre-industrial simulations: these may be judged as undesirable at the outset, but ultimately show value in suggesting that current models include the necessary physics to produce abrupt climate transitions, but exhibit incorrect sensitivity to the boundary conditions. Still, glacial climates are hypothesized to favour larger, more persistent transitions due to differences in large-scale wind patterns. Simplified models and idealized experimental setups may provide a means to constrain how the critical processes act, both in isolation and in combination, to destabilize the subpolar North Atlantic."

Caption: "Fig. 2. Map of the Northern Seas. Purple arrows represent surface currents, dashed orange arrows represent deep currents, and SPG indicates the subpolar gyre. Shading shows annual mean sea surface temperature (blues) and sea ice concentration (greys) from the NOAA Optimum Interpolation version 2 SST reanalysis (Reynolds et al., 2007)."

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Consequences / Re: Hurricane season 2018
« on: September 02, 2018, 10:12:12 PM »
I didn;t think much of the names picked for storms this year .. but Florence is welcome to drop by .. b.c.
The remains of Florence could give the UK its first Equinoxial storm in about a fortnight's time (if GFS is right for once on how and when Florence does the curve to the north and is then captured by the mid-latitudes Atlantic westerlies).

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