The Shortwave Radiative Flux Response to an Injection of Sea Salt Aerosols in the Gulf of Mexico

[Andrew Lockley]

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2022JD037067

Authors

P. B. Goddard,B. Kravitz,D. G. MacMartin,H. Wang

November 4th, 2022

Abstract

Marine cloud brightening (MCB) has been proposed as a potential means of geoengineering the climate, temporarily providing cooling to offset some of the effects of climate change. Marine sky brightening (MSB), involving direct scattering of sunlight from sea salt injection into the marine boundary layer, has been proposed as an additional geoengineering method that could work in areas that are not regularly cloudy. Here we use a regional atmospheric model to simulate MCB and MSB over the Gulf of Mexico and nearby land, a highly populated and economically important region that is not characterized by persistent marine stratocumulus cloud cover. Injection of sea salt in the Aitken mode from a region in the central Gulf of Mexico equivalent to 10.8 Tg yr-1 produces an upwards 8.4 W m-2 radiative flux change across the region at the top of the atmosphere, largely due to cloud property changes. Comparatively, a similar mass injection in the accumulation mode produces a 3.1 W m-2 radiative flux change driven primarily by direct scattering. Injection of even larger particles produces a much smaller radiative flux change. Shortwave flux changes due to clouds are largely driven by an increase in cloud droplet number concentration and an increase in cloud liquid water path (each contributing about 45% to the flux change), with a much lower contribution from cloud fraction changes (10%).

Source: AGU

[david....@carbon-cycle.co.uk]

Some questions:

 

1. I am assuming that we are talking about 10.8 Tg yr of sea water and not 10.8 Tg of salt. Is this correct?
2. To what height is the injection being modelled at?
3. Any idea of the predicted energy calculation for delivering and spraying this much material to this height?

 

 

David Sevier

 

Carbon Cycle Limited

248 Sutton Common Road

Sutton, Surrey SM3 9PW

England

 

Tel 44 (0) 208 288 0128

www.carbon-cycle.co.uk

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[Stephen Salter]

David

I attach the calculations for reversing sea level rise with marine cloud brightening. Some of the group will have seen them before although none have suggested corrections so far.

For the assumptions I have used (with which you may not agree with) we need to increase the number of condensation nuclei to reverse all historical sea level rise in a time of 20 years  by 2.87 times 10^24.

The salt mass per nucleus from a 0.8 micron liquid water diameter with 3.5% salinity is 10^ -14 grams so at any one time there should be an extra 0.29 Tg of salt in the atmosphere.

The salt stays there until the next rain.  Pick your own rainfall data.

Evaporation of spray will take lots of latent heat out of the air stream so the air will rapidly fall to the sea surface and spread out like a spilt liquid. The viscosity of air for this size of particle is like marbles in a fluid 100 times thicker that treacle so it cannot get into the water except for being scooped down by a breaker. Heat from the sea will warm the air and turbulence will spread it  fairly evenly through the marine boundary layer. You can experiment with cream in your coffee. If you speed up video of cloud patterns you will see rollers with a rotation period of about 20 minutes.

The second attached note from Schwartz and Slingo is a near painless account of Twomey with an immense amount of physics condensed into a non-linear scale of the nuclei increase factor.

Stephen

 

From: geoengi...@googlegroups.com <geoengi...@googlegroups.com> On Behalf Of david....@carbon-cycle.co.uk
Sent: 10 November 2022 16:12
To: andrew....@gmail.com; 'geoengineering' <geoengi...@googlegroups.com>
Subject: RE: [geo] The Shortwave Radiative Flux Response to an Injection of Sea Salt Aerosols in the Gulf of Mexico

 

This email was sent to you by someone outside the University.

You should only click on links or attachments if you are certain that the email is genuine and the content is safe.

Some questions:

 

1)      I am assuming that we are talking about 10.8 Tg yr of sea water and not 10.8 Tg of salt. Is this correct?

2)      To what height is the injection being modelled at?

3)      Any idea of the predicted energy calculation for delivering and spraying this much material to this height?

To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/01a901d8f51f%24213348b0%246399da10%24%40carbon-cycle.co.uk.

The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. Is e buidheann carthannais a th’ ann an Oilthigh Dhùn Èideann, clàraichte an Alba, àireamh clàraidh SC005336.

[Douglas MacMartin]

From Paul (lead author):

 

Q1 - 10.8 Tg/yr equivalent sea salt - see the 4^th paragraph in 2.2

Q2 - See last sentence of the first paragraph in 2.2 "Along with the model's background wind-dependent sea

salt emission flux, the additional sea salt particles in the experiments are initially added to the lowest atmospheric

layer and are not wind dependent."

Q3 - I did not calculate the energy requirement.

 

Cheers,

Paul

 

 

From: geoengi...@googlegroups.com <geoengi...@googlegroups.com> On Behalf Of david....@carbon-cycle.co.uk
Sent: Thursday, November 10, 2022 8:12 AM
To: andrew....@gmail.com; 'geoengineering' <geoengi...@googlegroups.com>

Subject: RE: [geo] The Shortwave Radiative Flux Response to an Injection of Sea Salt Aerosols in the Gulf of Mexico

 

Some questions:

 

1)      I am assuming that we are talking about 10.8 Tg yr of sea water and not 10.8 Tg of salt. Is this correct?

2)      To what height is the injection being modelled at?

3)      Any idea of the predicted energy calculation for delivering and spraying this much material to this height?

To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/01a901d8f51f%24213348b0%246399da10%24%40carbon-cycle.co.uk.