And yet another area where turning down the sun won’t have the same effect as stratospheric aerosols. (Since it has the opposite sign in the stratosphere.)
From: [email protected] [mailto:[email protected]] On Behalf Of Charles H. Greene Sent: Wednesday, May 11, 2016 7:40 PM To: Andrew Lockley <[email protected]> Cc: geoengineering <[email protected]> Subject: Re: [geo] Response of the AMOC to reduced solar radiation – the modulating role of atmospheric-chemistry Very interesting dynamical result, essentially mirroring the effects of Arctic amplification but by cooling lower latitudes to reduce the latitudinal temperature and geopotential height gradients. Thus, one might expect destabilization of the Polar Vortex, greater meandering of the Polar Jet Stream, and possibly higher frequencies of blocking events and extreme weather events in the mid latitudes. Also, in addition to effects on the AMOC, we might expect an increase in the frequency of Great Salinity Anomalies and their remote forcing of shelf marine ecosystems, especially in the NW Atlantic. These effects will likely be transient, like the ones we are observing now as the Arctic heats up and sea ice melts. I wonder what other surprises we would see, ones that the models don’t predict. Chuck Greene On May 11, 2016, at 1:49 PM, Andrew Lockley <[email protected] <mailto:[email protected]> > wrote: http://www.earth-syst-dynam-discuss.net/esd-2016-16/ Response of the AMOC to reduced solar radiation – the modulating role of atmospheric-chemistry Stefan Muthers, Christoph C. Raible, and Thomas F. Stocker University of Bern, Bern, Switzerland : 25 Apr 2016 Abstract. The influence of reduced solar forcing (grand solar minimum or geoengineering scenarios like solar radiation management) on the Atlantic meridional overturning circulation (AMOC) is assessed in an ensemble of atmosphere-ocean-chemistry-climate model simulations. Ensemble sensitivity simulations are performed with and without interactive chemistry. Without chemistry-climate interaction the AMOC is intensified in the course of the solar radiation reduction (SRR), which is attributed to the thermal effect of the solar forcing: reduced sea surface temperatures and enhanced sea ice formation increase the density of the upper ocean in the North Atlantic and intensify the deepwater formation. In simulations with chemistry-climate interactions a second, dynamical effect on the AMOC is identified which counteracts the thermal effect. This dynamical mechanism is driven by the stratospheric cooling in response to the reduced solar forcing, which is strongest in the tropics and leads to a weakening of the Northern polar vortex. In simulations with interactive chemistry, these stratospheric changes are strongly amplified by the reduction of stratospheric ozone. By stratosphere-troposphere interactions, the stratospheric circulation anomalies induce a negative phase of the Arctic Oscillation in the troposphere, which is found to weaken the AMOC through wind stress and heat flux anomalies in the North Atlantic. Neglecting chemistry-climate interactions in model simulations may therefore lead to an overestimation of the AMOC response to solar forcing. Citation: Muthers, S., Raible, C. C., and Stocker, T. F.: Response of the AMOC to reduced solar radiation – the modulating role of atmospheric-chemistry, Earth Syst. Dynam. Discuss., doi:10.5194/esd-2016-16, in review, 2016 -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected] <mailto:[email protected]> . To post to this group, send email to [email protected] <mailto:[email protected]> . Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected] <mailto:[email protected]> . Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
