Ocean temperature increase and hurricanes

[SkepticLance]

bascule

 

You need to re-read what I wrote. Your comments are quite misplaced, since they are based on complete lack of understanding of my post. When I ask a question, I expect an attempt at an answer rather than criticism for a perceived argument that is not actually there.

 

And sayonara.

There is a very big difference between distrusting a prediction and disbelieving a long term trend. I take great note of long term trends, as long as they are in the past, and recorded as good data. A predicted trend is something else. Mostly, (with a few exceptions where all details of the relevent science are known) predictions are unreliable. And the further into the future the prediction goes, the more unreliable it becomes.

Edited December 12, 2008 by SkepticLance

[Sayonara]

Yes, but pointing out that a prediction is unreliable to the nth degree is not sufficient justification for ignoring it. Although you are quite right in that that is not strictly relevant to this part of the discussion, that only holds true if the data you are querying comes from measurement and not modelling. Remember that past trends as well as future trends can be predicted.

[SkepticLance]

To sayonara

Re predictions of future warming.

The world is warming, and will continue to do so until something changes. That is a fairly reliable prediction.

 

I accept the need to make changes. I do not accept the need for idiotic and panicky responses due to a perceived need for rapid change. I do not think this will happen, mostly, though some things that have already happened are undesirable. The rather badly thought out Kyoto Protocol has led to actions that are undesirable - such as the development of a biofuel industry that destroys rainforests, and cuts food supplies.

 

There are a number of other actions under way that are far more desirable - such as research into electric vehicles, new generation nuclear power, development of new agricultural techniques, a reluctance to destroy forests, and a trend to planting more, and so on. Long may these trends continue, and let's not go down the road of actions that are destructive of human welfare, in response to a false perception of urgency.

[Sayonara]

I take it that you consider the transplantation of cities away from the coast to be such a panicky response?

 

I think it would probably take too much effort and time to be properly categorised as a knee-jerk reaction, but I still tend to agree. There are much more useful efforts that can be made.

[iNow]

I thought this graphic was insightful:

 

 

http://www.ncdc.noaa.gov/oa/climate/research/sst/ersstv3.php

 

The extended reconstructed sea surface temperature (ERSST) was constructed using the most recently available International Comprehensive Ocean-Atmosphere Data Set (ICOADS) SST data and improved statistical methods that allow stable reconstruction using sparse data. This monthly analysis begins January 1854, but because of sparse data the analyzed signal is heavily damped before 1880. Afterwards the strength of the signal is more consistent over time.

 

 

 

 

Also, a wealth of information here:

http://www.emc.ncep.noaa.gov/cmb/sst_analysis/

NOAA Optimum Interpolation Sea Surface Temperature Analysis

 

 

One last spiffy one:

http://ghrsst.jpl.nasa.gov/

The Global Data Assembly Center:

Portal to The GODAE High Resolution Sea Surface Temperature Pilot Project

Edited December 13, 2008 by iNow

[swansont]

Still leaves me with a question. How is it that, with an air temperature increase in the tropics of less than 0.5 C over 35 years, we get a water temperature increase of the same? If global warming is the mechanism, then air temperature will rise till the heat energy gets transferred to the sea, causing a water temperature increase, but with a big time delay.

 

I addressed this earlier. If the air temperature is higher than the water temperature, the air temperature need not change at all for the water temperature to increase. Your objection would be valid if the system were already in equilibrium, but it's not.

[JohnB]

Sorry for the delay. I've been playing catch up since I got back from holidays. (Went down to Melbourne to watch the World Latin American Dance Championships. Awesome.)

 

iNow, my graph on page 1 shows ACE, not number of storms. ACE is a function of number of storms, intensity and duration. The Accumulated Cyclone Energy index is falling.

 

Something I've noted while reading up on this is that depending on which metric you use, you get a different answer. For example, while ACE is falling, the Power Dissipation Index appears to be rising, yet both of these (for a season) use total number, intensity and duration of storms.

 

Another point to consider is that it becomes important where the authors of a paper live as the ROW doesn't use the American system of classification. While everyone uses the "Saffir-Simpson Hurricane Scale", the interpretations differ. The SSHS is based on sustained wind speeds. In the US this means sustained for 1 minute or more for a given 6 hour period. For most of the ROW, the requirement is for 10 minutes or more. This means that a storm classified as Cat 5 in the US may not be so classified elsewhere. It would also mean that the US would see more TC activity and in higher categories than the ROW.

 

However, since this should be consistent through history, it should have little bearing on trends in the NA and NEP regions.

 

I also note that using the ACE "Above Normal" is defined as above "115% of the current median" whereas "Below Normal" is defined as below "74% of the current median". Why this discrepancy exists, I don't know, but it obviously makes it much harder to have a below normal season than an above normal one. There could be some sort of loggerythmic scale involved, so for now I just accept it.

 

There also appears to be a lot of lattitude in what is meant by a "bad" season. Looking at the NA region, (hypothetically) is a season that spawns 4 Cat 5 cyclones that last for 6 hours and never make landfall worse that one that spawns 12 Cat 3 cyclones that all make landfall and last for 3 days each? The devil is in the details.

 

Terminologies also differ. Is a "Named Storm" the same thing as a "Tropical Storm"? It would appear to be "yes", but I can't be sure.

 

If we look at this NOAA page "Atlantic Hurricane Season Sets Records", we see a listing of 16 named storms, 8 hurricanes and 5 major hurricanes for the 2008 season. NOAA conclude that 2008 ties as 4th most active since 1944.

 

Comparing this with the ACE list at Wiki, we see a different picture. The numbers are still the same @ 16, 8 and 5 but 2008 is 15th on the list with an ACE of 142. It ties as 6th for Tropical Storms, 10th (with 2004 and 1999) for hurricane number and 8th (with 1995, 1999 and 1969) for major hurricanes.

 

We also see Weather dot com calling the 2008 season an "all time record breaker". This would appear to be based on "5 of the 6 months of hurricane season had a major hurricane", since there were no Cat 5s in 2008. Again, interpretation; Is one a month for 5 months worse than 2 a month for 4 months? (1950 had 8 MH in it's season.)

 

As an aside, Hurricane San Ciriaco in 1899 had an ACE of 73.57 which is higher than the entire 2007 Hurricane Season (72). That was one hell of a storm.

 

It is also interesting to note that the rather poor 2007 season (ranking 40th in ACE) actually spawned 2 Cat 5 Hurricanes. Full numbers being 15 TS, 6 H and 2 MH.

 

Another interesting point to consider is that out of the last 18 years, only 6 have spawned Cat 5 Hurricanes, 1992, 1998, 2003, 2004, 2005 and 2007. 1991, 1993, 1994, 1995, 1996, 1997, 1999, 2000, 2001, 2002, 2006 and 2008 had none. Comparing that to the current plateau in world temps shown by HADCRUT, there would certainly appear to be a correllation with some sort of threshold being crossed around 1999 WRT Cat 5 generation. Interesting.

 

Bottom line is, it would appear that you could prove just about anything depending on which metric you use and how you interpret the original data. I don't have a degree, but I didn't think science was supposed to work that way.

[Pangloss]

JohnB, that was interesting, but I think that just as you have to take dire declarations about human contribution to hurricane intensity with a grain of salt, I think you also have to take logical reasoning against human contribution to hurricane intensive with a grain of salt. There are just too many variables. For instance, this wasn't an El Nino year, and yet it was still a very strong and active season, meeting or exceeding most of the pre-season predictions. What if it had been an El Nino year? What if there had been a few more Cat 5s? Would that actually prove anything either way? Science has to be the guide for both sides of the GW question.

 

I agree with you, though, that the number of months in which a hurricane occurs is a near-worthless statistic. Similarly, damage statistics in human lives and monetary cost also seems worthless for measuring the influence of GW. Just fodder for the 6 o'clock news.

[iNow]

Interesting information. Thanks, John. It sounds, however, like we CAN still very much show trends as long as we use a consistent data set. If I interpret your post correctly, the only difference is that some people are calling it six and others calling it half a dozen. Or, some people calling a pair of pants "sexy" versus another group callng them "slutty." They are the same pants, and that is where we should focus.

 

I'm personally inclined to go with the one used in the primary literature, and NOAA, as the ACE data seems to be in a hole.

[JohnB]

as the ACE data seems to be in a hole.

I got the "concentrating on the pants" immediately, but I was making coffee before I got this one. Has your wife ever threatened to thump you with something?

 

NOAA uses the ACE Index, that's why I don't get how 2008 ranks 4th historically according to NOAA. BTW, they keep a complete listing of yearly ACE here. It is disappointing that they can't keep it up to date as it ends with the 2006 values, surely they've had the time to at least input the 2007 values?

the only difference is that some people are calling it six and others calling it half a dozen.

Not quite, ACE and PDI are both based on frequency, duration and number of storms but PDI uses the cubed power for wind velocity and includes area covered, this would appear to give a heavier weighting to higher category storms.

 

PDI hasn't been around long as it was developed by Dr. Emanuel in his 2005 "Letter to Nature", where he builds on his previous letter. Are "Letters to Nature" peer reviewed? I don't think the GRL ones are, so these may not be. I don't know.

 

Anyhoo, Emanuel 2005 states a doubling of PDI in the 30 years to 2005 and frankly, the ACE doesn't agree. So we have two metrics that appear to be diametrically opposed.

 

To further confuse things, Roger Pielke Jr in another Nature communication states that;

Emanuel reports a marked increase in the potential destructiveness of hurricanes based on identification of a trend in an accumulated annual index of power dissipation in the North Atlantic and western North Pacific since the 1970s. If hurricanes are indeed becoming more destructive over time, then this trend should manifest itself in more destruction. However, my analysis of a long-term data set of hurricane losses in the United States shows no upward trend once the data are normalized to remove the effects of societal changes.

NOAAs Tom Knutson tends to agree. However both of these gentlemen are referring to landfalling TCs. Figure 1 in Dr. Knutsons paper is taken from Landsea 2005 and shows no increase. (The 2005 season being an obvious outlier.) It strikes me as highly implausable that total "energy" for a season could double over 30 years without some increase being visible in the landfall stats. Did all the extra storms stay at sea or something?

 

There was quite an argument in 2005 over this matter with Landsea commenting in Nature;

I question his analysis on the following grounds: it does not properly represent the observations described; the use of his Atlantic bias-removal scheme may not be warranted; and further investigation of a substantially longer time series for tropical cyclones affecting the continental United States does not show a tendency for increasing destructiveness. These factors indicate that instead of "unprecedented" tropical cyclone activity having occurred in recent years, hurricane intensity was equal or even greater during the last active period in the mid-twentieth century.

Ouch!

 

I note that Emanuel cowrote a paper with RCs Michael Mann in 2006 titled Atlantic Hurricane Trends Linked to Climate Change. In this EOS article they find;

There is a strong historical relationship between tropical Atlantic SST and tropical cyclone activity extending back through the late nineteenth century. There is no apparent role of the AMO.

This would appear to be at odds with NOAA who state;

NOAA attributes this increased activity to natural occurring cycles in tropical climate patterns near the equator. These cycles, called “the tropical multi-decadal signal,” typically last several decades (20 to 30 years or even longer). As a result, the North Atlantic experiences alternating decades long (20 to 30 year periods or even longer) of above normal or below normal hurricane seasons. NOAA research shows that the tropical multi-decadal signal is causing the increased Atlantic hurricane activity since 1995, and is not related to greenhouse warming.

I also find it interesting that Mann & Emanuel 2006 uses an increase in anthropogenic aerosol forcings to make things fit. Aerosols levels have been falling. That is the usual argument for the temp rise at the end of the 1940-1975 cooling period isn't it? They argue for "the regional enhancement of

anthropogenic tropospheric aerosol cooling". Hmm. I also note they attribute their aerosols to Crowley 2000. While Crowley also uses an increasing negative forcing due to aerosols, he doesn't seem to provide a source. (Yes, he does link to the RF data, but not where he got it from.) Crowley shows an increasing negative forcing going from -0.58600 W/M2 in 1980 to -0.70100 W/M2 in 1998. It's this sort of thing that gives me headaches.

 

Back on topic. I think it's fair to say that there has been an increase in intense TCs. Of the 6 seasons that spawned Cat 5s, 4 were in the last 8 years. Theory tells us that with an increase of SST we should see an increase also in TS generation, simply because there is more water above the threshold temp for a longer time. How this reconciles with no observed increase in activity and a low ACE, I have no idea. There must be another factor involved somewhere.

 

I wonder if the rise in air temp causes an increase in wind shear, which appears to be a mitigating factor in the growth of a TC?

[iNow]

I got the "concentrating on the pants" immediately, but I was making coffee before I got this one. Has your wife ever threatened to thump you with something?

I'm glad. I wasn't sure if you'd catch that. And, she's still my girlfriend, but she does far more than threaten, and I have the bruises and scars both to prove her "appreciation" for my humor.

 

 

 

 

 

Back on topic. I think it's fair to say that there has been an increase in intense TCs. Of the 6 seasons that spawned Cat 5s, 4 were in the last 8 years. Theory tells us that with an increase of SST we should see an increase also in TS generation, simply because there is more water above the threshold temp for a longer time. How this reconciles with no observed increase in activity and a low ACE, I have no idea. There must be another factor involved somewhere.

First, let me say that was an excellent post, John. You took your time to lay out clearly the issue and describe what you'd read, and I really appreciate it. This does, indeed seem to be another factor somewhere missing in these arguments. What stands out most to me, however, is both a) that increasing SSTs by definition feed increasing strengths of TCs, and b) that these past 8 years have seen so many more Cat 4 & 5 storms than in years previous. Not enough for certainty, but I'm most certainly inclined to tend toward the fact that something is feeding these more intense storms and that AGW seems the most likely and plausible explanation.

 

 

 

I wonder if the rise in air temp causes an increase in wind shear, which appears to be a mitigating factor in the growth of a TC?

I agree with your conjecture. Wind shear seems vitally important based on all I've read, but I'm not formally training so welcome further insight and evidence either way.

 

Thanks again, dude. I'll try to pay closer attention to these apparent contradictions that you've so rightly drawn attention to. Cheers.

Edited December 23, 2008 by iNow
multiple post merged

[JohnB]

but she does far more than threaten, and I have the bruises and scars both to prove her "appreciation" for my humor.

Sounds like my wife. Her most commonly used threat is "I'll beat you, and not in a good way.":D

 

Just furthering the conjecture a bit.

1. In 2005 Katrina was a low grade hurricane until it got to the Gulf of Mexico where it strengthened to a monster.

 

2. On most maps of warming, the most severe is in the region containing the CONUS, NA and Europe. This makes sense since the two land regions are arguably the most highly industrialised and urbanised areas on the planet.

 

I wonder how much heat rivers are dumping into the ocean?

 

Think about a summer storm over a city. It's a hot day and in the afternoon the rain comes and cools everything down. How? The rain has absorbed the heat from the air, the roofs of houses and the roads. This much warmer water goes into the storm drains and directly into the waterways.

 

How much warmer is the Mississippi today compared to 100 years ago? This heat runoff is fed directly into the Gulf waters. This happens with all rivers of course, but most empty into an ocean whereas the Gulf is almost totally landlocked.

 

My conjecture is that this heat runoff is causing a disproportionate increase in temps in the Gulf, logically leading to a disproportionate strengthening of any hurricane that spends too much time there. The slower moving the hurricane, the stronger it gets.

 

I don't know how to prove the idea, but I don't seem to see it discussed anywhere in the literature.

 

It's like cars, I can't help but think that the straight heat output of hundreds of millions of cars each dumping tens of thousands of litres of extremely hot air directly into the atmosphere every day must have some sort of effect. (Beyond being lumped into the UHI index.)

 

Like you, I'm not formally trained either. I have a laymans idea of science. I expect scientific comments to be along the lines of; "This is what we think and here is the data that shows why we think this." This is one reason why I look at things like the Emanuel PDI letter with reserve. I can see two reasons for creating a new metric;

1. The ACE that everybody uses should show an increase and does not, therefore it is incomplete and we need a new metric that does. or

2. The ACE that everybody uses should show an increase and does not, therefore we need a new metric that does to bolster our arguments.

 

I'm sceptical when someone in the "warmer" camp comes up with a "new" anything that shows things as worse than expected just as I'm sceptical if someone in the "denier" comes up with a "new" something showing things better than expected. Creating new things to back an argument because the widely accepted metrics don't is immediately suspect in my view. Time may show that the "new" thing is indeed needed, but it's definitely starting from a handicapped position IMO.

 

BTW, does anyone know if "Letters to Nature" are peer reviewed? If not, then PDI is a non-peer reviewed metric and should be given less weight because of that fact. If they are, cool, but then the contradiction still remains.

Edited December 24, 2008 by JohnB

[iNow]

Interesting idea about the rivers. It made me recall how much fertilizer and chemicals we are pouring into the oceans via rivers (which collect run-off from rains on land).

 

That fertilizer would feed the algae and plankten in the ocean, and that increased growth (rate and scope) may cause additional warming of ocean waters. [/conjecture]

 

 

Hmmm...

[SkepticLance]

iNow

Most speculation I have seen on this topic is that fertilising the ocean will have the opposite effect. Phytoplankton growth is stimulated, and the increased biomass absorbs CO2. Some of this, presumably sinks to the bottom of the sea and adds to the carbon sink in the abyss. Of course, this is still unproven.

[iNow]

iNow

Most speculation I have seen on this topic is that fertilising the ocean will have the opposite effect. Phytoplankton growth is stimulated, and the increased biomass absorbs CO2.

 

Thanks, Lance. I have seen that data, and agree with the concept. However, my point was specific to the effect on ocean temperatures, not CO2 content in the atmosphere.

[scalbers]

Actually the ocean fertilization might just be a temporary benefit in moving CO2 into the ocean sooner. Since the ocean systems ultimately have limited capacity to absorb carbon this might just hasten the day that oceans help slow the growth of atmospheric carbon?

 

In other words if we use the "biological pump" to move carbon to the ocean bottom, this will in effect do the mixing that normally takes about 1000 years in a shorter period of time. Once the ocean is mixed then CO2 uptake slows down quite a bit.

[iNow]

One of the problems with that idea, scalbers, would be the creation of dead zones where high rates of plankton growth cause an anoxic environment.

 

 

http://daac.gsfc.nasa.gov/oceancolor/scifocus/oceanColor/dead_zones.shtml

"Dead zones" in this context are areas where the bottom water (the water at the sea floor) is anoxic — meaning that it has very low (or completely zero) concentrations of dissolved oxygen. These dead zones are occurring in many areas along the coasts of major continents, and they are spreading over larger areas of the sea floor. Because very few organisms can tolerate the lack of oxygen in these areas, they can destroy the habitat in which numerous organisms make their home.

 

The cause of anoxic bottom waters is fairly simple: the organic matter produced by phytoplankton at the surface of the ocean (in the euphotic zone) sinks to the bottom (the benthic zone),where it is subject to breakdown by the action of bacteria, a process known as bacterial respiration. The problem is, while phytoplankton use carbon dioxide and produce oxygen during photosynthesis, bacteria use oxygen and give off carbon dioxide during respiration. The oxygen used by bacteria is the oxygen dissolved in the water, and that’s the same oxygen that all of the other oxygen-respiring animals on the bottom (crabs, clams, shrimp, and a host of mud-loving creatures) and swimming in the water (zooplankton, fish) require for life to continue.

 

The "creeping dead zones" are areas in the ocean where it appears that phytoplankton productivity has been enhanced, or natural water flow has been restricted, leading to increasing bottom water anoxia. If phytoplankton productivity is enhanced, more organic matter is produced, more organic matter sinks to the bottom and is respired by bacteria, and thus more oxygen is consumed. If water flow is restricted, the natural refreshing flow of oxic waters (water with normal dissolved oxygen concentrations) is reduced, so that the remaining oxygen is depleted faster.

 

 

 

 

 

 

 

Also, it appears that as the ocean absorbs more and more CO2 that it's ability to continue absorbing more decreases.

 

http://www.sciencemag.org/cgi/content/abstract/1136188

Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change

 

Based on observed atmospheric carbon dioxide (CO2) concentration and an inverse method, we estimate that the Southern Ocean sink of CO2 has weakened between 1981 and 2004 by 0.08 petagrams of carbon per year per decade relative to the trend expected from the large increase in atmospheric CO2. We attribute this weakening to the observed increase in Southern Ocean winds resulting from human activities, which is projected to continue in the future. Consequences include a reduction of the efficiency of the Southern Ocean sink of CO2 in the short term (about 25 years) and possibly a higher level of stabilization of atmospheric CO2 on a multicentury time scale.

 

 

In case you don't have a subscription to read the full article at Science, you can read more about it here:

 

http://www.sciencedaily.com/releases/2007/05/070517142558.htm

Scientists have observed the first evidence that the Southern Ocean’s ability to absorb the major greenhouse gas, carbon dioxide, has weakened by about 15 per cent per decade since 1981.

 

In research published in Science, an international research team – including CSIRO’s Dr Ray Langenfelds – concludes that the Southern Ocean carbon dioxide sink has weakened over the past 25 years and will be less efficient in the future. Such weakening of one of the Earth’s major carbon dioxide sinks will lead to higher levels of atmospheric carbon dioxide in the long-term.

[scalbers]

Yes inow, I take it you agree with me this wouldn't be a good idea overall, just some limited atmospheric CO2 benefit in the short-term and even that is outweighed by other problems that you are providing good details about.

 

My main point is that the proposed fertilization would hasten the day that the deep ocean sinks weaken.

[SkepticLance]

There is a bit of confusion here, I think. The ocean's ability to absorb CO2 is generally the ability to dissolve it. When iron or other fertiliser is added to the oceans, a different mechanism comes into play. Enhanced phytoplankton growth converts CO2 into organic compounds. A small part of this is supposed to sink and become part of the deep ocean carbon sink. As I said before, this is unproven, and the value of fertilisation is problematic. However, it is NOT the same as the ocean's ability to absorb CO2. If it works, it would have quite different limits.

 

The fertilisation need not create anoxic spots. If the iron or other effective fertiliser is spread over wider parts of the deep oceans, instead of concentrations in shallower waters as currently happens in the Gulf of Mexico, which is just a matter of good management of the technique, then anoxic spots will not form, but fertilisation will occur. However, I am not convinced the technique has merit. Time and research are needed.

[iNow]

The fertilisation need not create anoxic spots. If the iron or other effective fertiliser is spread over wider parts of the deep oceans, instead of concentrations in shallower waters as currently happens in the Gulf of Mexico, which is just a matter of good management of the technique, then anoxic spots will not form, but fertilisation will occur.

 

Since this was quoted in my source above:

 

The cause of anoxic bottom waters is fairly simple: the organic matter produced by phytoplankton at the surface of the ocean (in the euphotic zone) sinks to the bottom (the benthic zone),where it is subject to breakdown by the action of bacteria, a process known as bacterial respiration. The problem is, while phytoplankton use carbon dioxide and produce oxygen during photosynthesis, bacteria use oxygen and give off carbon dioxide during respiration. The oxygen used by bacteria is the oxygen dissolved in the water, and that’s the same oxygen that all of the other oxygen-respiring animals on the bottom (crabs, clams, shrimp, and a host of mud-loving creatures) and swimming in the water (zooplankton, fish) require for life to continue.

 

 

... the mechanism itself is quite clear. We know without a doubt that adding fertilizer has a specific effect, and there is no disagreement on that.

 

 

This means that your comment can only be referring to scale/magnitude. The implicit suggestion of your post is that if add "just enough" or if we "do it just right," it won't have the negative effects described.

 

Please provide precise numbers (add x fertilizer, get y growth and z oxidation), and also the tipping points/thresholds between positive and negative effects, or discontinue this line of conversation as it will only distract us from the truth we already have available, which we each understand, and on which we all agree.

 

Present the numbers, Lance, or present nothing. Make that your Christmas present to the readers of this forum, will you?

[scalbers]

There is a bit of confusion here, I think. The ocean's ability to absorb CO2 is generally the ability to dissolve it. When iron or other fertiliser is added to the oceans, a different mechanism comes into play. Enhanced phytoplankton growth converts CO2 into organic compounds. A small part of this is supposed to sink and become part of the deep ocean carbon sink. As I said before, this is unproven, and the value of fertilisation is problematic. However, it is NOT the same as the ocean's ability to absorb CO2. If it works, it would have quite different limits.

 

 

Yes, this sinking to the deep ocean is the biological pump I referred to in post 91. Ultimately all the carbon on a thousand year time scale ends up in the same place. The processes of mixing and decomposition ends up producing an equilibrium concentration (I think of carbonic acid) in the ocean and this in turn is in equilibrium with the atmosphere. One might hasten the oceanic uptake of carbon in the short term with fertilization, but the long term limit remains the same. So therefore we have no long term benefit of ocean fertilization.

 

In fact we are simply hastening the day that we have set up a long term acidification of the ocean.

[SkepticLance]

scalbers

Equilibrium relates more to movement into and out of solution. When organic matter falls to the ocean bottom, it enters a carbon sink long term (millions of years) and is not returned to the atmosphere for a very long time. In human time spans, this is not equilibrium. It is removal.

[scalbers]

SkepticLance,

 

Off-hand I think this might be stated differently, since over the 1000 year time scale carbon that falls towards the deep ocean may decompose or dissolve, then mix back to the surface waters and atmosphere. It's unclear to me how much of the carbon would fall all the way to the sea floor and not be metabolized or dissolved or somehow end up back into the ocean waters. It would have to sit on the ocean floor for many thousands of years before geological "removal" would take place.

Edited December 27, 2008 by scalbers

[SkepticLance]

scalbers

Your logic is good, and your conclusion mostly correct. As I said before, only a small part of the carbon taken up by phytoplankton will go into long term carbon storage. This small part drifts to the ocean bottom and gets covered by sediment. From my reading, it appears that a hell of a lot of carbon is already stored beneath deep ocean sediment.

 

As far as I am aware, no-one has determined how much of phytoplankton biomass ends up this way, and this casts a mass of uncertainty over the idea of deep ocean fertilisation.

[scalbers]

Yes, the fraction of the carbon that gets bound up in sediments and geologically sequestered would be important to consider. As a thought experiment lets assume it is reasonably large - about .33. I would submit that this might not be large enough to be beneficial since the remainder (.67) would still reside in the ocean/atmosphere system over a 1000 year time scale and would still be contributing to global warming and ocean acidification. It would be better to have not emitted it in the first place, or perhaps sequester it in soils instead. Or even mechanical sequestration in the ocean sediment if that can be trusted.

 

In other words, ocean fertilization may have a short term atmospheric CO2 reduction over a few decades or centuries, but would likely be quite limited in terms of a reduction 1000 years out. The levels at the 1000 year time scale are longer than human lifetimes, though still worth considering in my view.

 

In the short term this may also increase deep ocean acidification for those lifeforms that exist there.

 

On a separate note, there could be unintended ecological disruptions caused by ocean fertilization.

Edited December 27, 2008 by scalbers