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Comments 26 to 50 out of 99:

26. Rob Painting at 21:31 PM on 5 December, 2010
    Most references I see on coral bleaching list increased temperature as the main stress likely to cause it. Reading the wiki on Coral bleaching seems to offer a contradiction Not really. Coral reef bleaching can be induced by a number of conditions- as listed in the Wiki page. The bleaching events I have previously linked to are truly massive in scale and correspond with anomalously warm, and sustained, sea surface temperatures. Hence the ability to predict these large bleaching events in advance. If you pore over the peer-reviewed literature you will see a lot of debate about the cause in earlier years, however as global warming, and warming ocean temperatures have continued, the evidence identifying warming SST's has strengthened. Try reading the first link I provided at @ 19. The lead author, Eakin, has published a lot of work on corals, and the study gives a good overview.
27. Rob Painting at 22:03 PM on 5 December, 2010
    That seems to say that CO2 is required for photosynthesis. Yes, same for "sea plants" as it is for land based ones. The carbon in the CO2 molecule provides the basis for carbohydrates which are synthesized using energy from the sun.
28. muoncounter at 04:13 AM on 6 December, 2010
    #24: "Coral bleaching is a vivid sign of corals responding to stress," Let's walk down your stress list point by point: a. increased (most commonly), or reduced water temperatures -- emphasis added b. increased solar irradiance (photosynthetically active radiation and ultraviolet band light) -- not happening, unless you live under an ozone hole c. changes in water chemistry (in particular acidification) -- yes, that happens when CO2 concentration increases and is the point of this thread c. starvation caused by a decline in zooplankton -- do they die due to lowered pH? d. increased sedimentation (due to silt runoff) -- local effects only e. pathogen infections -- chicken and egg here, increased stress leads to greater susceptibility to infection f. changes in salinity -- most likely local (we'd notice it globally) g. wind -- random, at best h. low tide air exposure -- sea level is rising i. cyanide fishing -- whatever that means So the winner is ... most commonly temperature, acidification "CO2 appears to be essential for coral photosynthesis?" Corals are Cnidaria ... (animals). We don't do photosynthesis.
29. cjshaker at 05:53 AM on 6 December, 2010
    Muoncounter: you might want to read replies from Rob Painting. Coral is a symbiotic organism, basically an algae inside the animal. The algae provides energy for the coral from photosynthesis. Chris Shaker
30. cjshaker at 05:57 AM on 6 December, 2010
    I remain curious as to why coral are so temperature sensitive, considering that they have evolved during millions of years of the glacial cycle? As of 1950, we were still 4.5C short of the temperature high achieved during the previous warming phase. The glacial cycle causes large climate changes. Why have coral not evolved to be more flexible about temperature? Chris Shaker
31. Rob Painting at 05:59 AM on 6 December, 2010
    Muoncounter - We don't do photosynthesis. The corals in shallow water reefs are a symbiosis between the coral polyp and photosynthesizing algae. The algae provide nutrients to the polyp via photosynthesis and in exchange get shelter and protection. Typically too warm waters (above the photo-symbiont's tolerance) leads to a shut down in photosynthesis and because they are no longer getting food, the polyps expel the algae, hence the "bleaching" of colours which the algae produce. So although the polyp may not photosynthesize, it is certainly dependent on it for survival.
32. Rob Painting at 06:04 AM on 6 December, 2010
    I remain curious as to why coral are so temperature sensitive Chris, were the Earth (and sea temperatures) not warming so rapidly, it's likely that coral would be able to adapt, by acquiring less temperature sensitive photo-symbionts. Like other changes in the Earth system, it's the speed of change that is the problem.
33. cjshaker at 06:14 AM on 6 December, 2010
    Rob I've been reading about dramatic temperature changes in the recent past, documented from temperature proxy data retrieved from the ice cores. http://www.scientificamerican.com/article.cfm?id=ice-core-reveals-how-quickly-climate-can-change "Following this abrupt shift, as much as 20 degrees Fahrenheit (10 degrees Celsius) of warming occurred over the subsequent decades—a change that ultimately resulted in at least 33 feet (10 meters) of sea-level rise as the ice melted on Greenland." http://www.sciencedaily.com/releases/2008/06/080619142112.htm "The ice core showed the Northern Hemisphere briefly emerged from the last ice age some 14,700 years ago with a 22-degree-Fahrenheit spike in just 50 years, then plunged back into icy conditions before abruptly warming again about 11,700 years ago. Startlingly, the Greenland ice core evidence showed that a massive "reorganization" of atmospheric circulation in the Northern Hemisphere coincided with each temperature spurt, with each reorganization taking just one or two years, said the study authors." These seem like pretty massive and rapid climate changes to me. Chris Shaker
    Response: This discussion has drifted off the topic of this thread. Everybody please start commenting on the appropriate threads.
34. scaddenp at 06:49 AM on 6 December, 2010
    I responds to this over on #148 of "we're heading into an ice age".
35. cjshaker at 18:04 PM on 6 December, 2010
    scaddenp: I put the sources detailing recent dramatic temperature shifts here, because we're talking about the inability of coral to deal with dramatic temperature shifts. It seemed surprising to me. Chris Shaker
36. Rob Painting at 18:30 PM on 6 December, 2010
    These seem like pretty massive and rapid climate changes to me. Indeed, they would affect any coral reefs growing around Greenland. I'm not aware there was, but if there was. Moderator: There isn't a coral rebuttal or post (yet). I didn't realize all those coral "arguments" existed.
37. Rob Painting at 23:40 PM on 6 December, 2010
    Chris Shaker, The changes in tropical temperatures during the glacial/inter-glacials was much smaller than the global average, "probably" 1-2 degrees change. Most of the large temperature swings occurred at high latitudes and especially the Northern Hemisphere where continental ice sheets formed. This small change is temperature in the tropics is why the tropical rainforests were not greatly affected by the ice ages. Precessional changes (wobbles in the Earth's rotation) which affect the amount of solar radiation at the equator are thought to have had a greater significance. Localized coral bleaching is not a new phenomenon, however mass coral bleaching is, certainly within the last several hundred thousand years.
38. cjshaker at 06:24 AM on 7 December, 2010
    Rob: Do we have good temperature proxy data from the tropics? Sea floor cores, or such? Do the glacial cycles show up there, too? Chris Shaker
39. muoncounter at 03:02 AM on 15 December, 2010
    Follow up from here. Excellent link posted by RSVP. Ocean CO2 concentrations on the increase, as of 2006 Odd, the largest changes in the Atlantic are in the northern hemisphere, the Indian is worse in the south, but the Pacific seems even.
    Response: I take back the 'excellent link' opinion. The website has an extensive page in denial of AGW.
40. muoncounter at 10:22 AM on 15 December, 2010
    I'm not understanding this ocean acidifying-ocean CO2 feedback question. Oceans are indeed acidifying as they absorb atmospheric CO2, as the figure above shows. From Caldeira and Wickett 2005: The SRES pathways considered here produce global surface pH reductions of about 0.3 to 0.5 pH units by year 2100. ... Atmospheric emissions of 5000 Pg C and 20,000 Pg C produce global surface pH reductions of 0.8 and 1.4 pH units, respectively by year 2300. We depend on these CO2 sinks to take up to 50% of our fossil fuel waste product out of the atmosphere each year. There's evidence that ocean sinks are weakening, as in LeQuere et al 2007: 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 ... How is it possible for oceans to simultaneously absorb and emit CO2?
41. michael sweet at 10:40 AM on 15 December, 2010
    RSVP, Coming in from the cool ice data thread. Three factors of ten is ten times ten times ten or one thousand times different. The pH affects the different ion distribution as Stephen Baines points out. The pH in fresh water with CO2 dissolved is around 5 and the pH in the ocean is around 8 or 1000 times less hydrogen ions. This affects the carbonate concentration and therefore the solution of CO2. N2 and O2 are not pH sensitive. That is part of why Henry's law seems to not work according to your calculations. As I said here and Alec said here, carbon dioxide is soluble in water and O2 and N2 are not. Because CO2 is soluble in water its properties are different from O2. The calculations are very difficult (I have not done them) and to get better than a qualatative answer you will have to read the peer reviewed literature. My understanding is that research continues to estimate how much CO2 the ocean can absorb before it is saturated. (Currently the ocean is absorbing CO2 as the concentration increases according to Henry's law. The warming of the ocean is not as important today as it was in the past) CO2 running out: stop speculating about processes you do not understand. We better pray that the CO2 in the ocean never outgasses enough to run out. There is an enormous amount of CO2 in the ocean and the surrounding land would start to dissolve as the CO2 outgasses. That would be Venus for sure.
42. Stephen Baines at 12:16 PM on 15 December, 2010
    @ muoncounter. "I'm not understanding this ocean acidifying-ocean CO2 feedback question." As I understand it RSVP is claiming (incorrectly) that there can be no CO2 oceanic solubility feedback during northern latitude warming phases of Milenkovitch cycles because outgassing from warming oceans would have resulted in similar relative increases in CO2, N2 and O2. Summing up succinctly, RSVP fails to understand that the pool of exchangeable CO2 in the ocean is very large relative to that in the atmosphere (for a number of reasons), while the opposite is true for N2 and O2. As a consequence, outgassing from a warmer ocean affects atmospheric CO2 concentrations significantly, but it does not affect N2 and O2 concentrations in any measureable way. As far as I can tell, pH only comes into the discussion because of its effect on the relative abundance of carbonic acid, bicarbonate and carbonate ions (and protons) as temp changes the solubilty of CO2.
43. muoncounter at 14:00 PM on 15 December, 2010
    #42: "outgassing from a warmer ocean affects atmospheric CO2 concentrations significantly" I'm not referring to RSVP's mathiness. Papers are practically screaming that the oceans are sucking up CO2 to what will become dangerous levels (at least to plankton) in not very many years. From McNeil and Matear 2008, Southern Ocean acidification via anthropogenic CO2 uptake is expected to be detrimental to multiple calcifying plankton species by lowering the concentration of carbonate ion (CO3^-2) to levels where calcium carbonate (both aragonite and calcite) shells begin to dissolve. ... Southern Ocean wintertime aragonite undersaturation is projected to occur by the year 2030 and no later than 2038. On the other hand, the language of outgassing is very complicated, as in Lovenduski et al 2006: In contrast, there is a simultaneous anomalous uptake of anthropogenic CO2 during a positive phase of the SAM in the southernmost regions of the Southern Ocean, due to increased upwelling of deep, older waters and their subsequent exposure to higher atmospheric CO2 levels. The anthropogenic uptake only slightly mitigates the natural outgassing from the Southern Ocean, so that a positive SAM is associated with anomalous outgassing of contemporary CO2. In a future characterized by higher atmospheric CO2, however, positive phases of the SAM may be associated with a greater oceanic uptake of anthropogenic CO2. And they say clouds are complicated beasts?
44. Stephen Baines at 16:25 PM on 15 December, 2010
    Ah, I see your problem. The simple (probably non-informative answer) answer is that the ocean is heterogeneous. Depending on where you are it can be a source or a sink for CO2. What increasing atmospheric CO2 concentration has done is to shift that balance uniformly toward the sink side of things. Still, there are large areas where upwelling of deep, CO2 rich water and limited phytplankton growth (often due to relatively low Fe availability) results in surface waters that are supersaturated with CO2. This is particularly true in the Eastern Equatorial Pacific because the cold CO2-rich waters warm significantly after reaching the surface, making them even more supersaturated. It's the largest natural source of CO2 on the planet. In the Southern Ocean things are more complicated because the deep water upwells vigorously there and can be subducted beneathe warmer, light water after moving northward, or can sink to great depths if it gets particularly cold and salty after moving south. I need to read the paper when I have time, but the quote you cite seems to have something to do with the fact that under positive SAM and steady state CO2 conditions, vigorous upwelling brings CO2 rich water continually to the surface where it can lead to net evasion of CO2 on the whole. However, in some places there may net uptake of CO2, or net evasion depending on initial CO2, the evolution of water temperature and mixing with surrounding waters. Under higher atmospheric CO2 levels, though, the net flux would be into the ocean across the Southern Ocean because, while the atmopsheric concentration is changing, the concentration in the upwelled water stays constant because it reflects past atmospheric conditions 200-1000 years ago. If that difference is high enough, then the same vigorous upwelling during SAM could actually enhance net storage of CO2 by continuously bringing new undersaturated water to the surface across the entire region where it can soak up CO2 and then sink to depth again.
45. RSVP at 19:43 PM on 15 December, 2010
    michael sweet #41 "stop speculating about processes you do not understand" Thanks for answering my question. In reading 41, 42, 43, and 44 it becomes clear that the problem is not simple.
46. Rob Painting at 22:27 PM on 15 December, 2010
    Muoncounter - How is it possible for oceans to simultaneously absorb and emit CO2? The temperature of the ocean is heterogeneous too. Generally the flux of CO2 to the atmosphere originates from the tropical regions where the ocean is warmer and CO2 less soluble. The uptake is occurring in the larger region of cooler waters where CO2 is more soluble. Much more complicated than that of course, as others have already pointed out, but why over-complicate matters?. The overall effect of human fossil fuel combustion is to increase CO2 dissolved into the oceans at a rate that is unprecedented. Papers are practically screaming that the oceans are sucking up CO2 to what will become dangerous levels (at least to plankton) in not very many years. From McNeil and Matear 2008 The Arctic Ocean is projected to reach aragonite (more soluble form of calcium carbonate) undersaturation within a decade, meaning the waters will be corrosive to calcifying marine organisms that make their shells from aragonite. Imminent ocean acidification in the Arctic projected with the NCAR global coupled carbon cycle-climate model "Aragonite undersaturation in Arctic surface waters is projected to occur locally within a decade and to become more widespread as atmospheric CO2 continues to grow. The results imply that surface waters in the Arctic Ocean will become corrosive to aragonite, with potentially large implications for the marine ecosystem, if anthropogenic carbon emissions are not reduced and atmospheric CO2 not kept below 450 ppm." It amazes me how little attention is being given to such a serious issue. It will have profound effects for life on Earth, and the changes to ocean chemistry are pretty much irreversible for many ten of thousands of years.
47. Stephen Baines at 04:08 AM on 16 December, 2010
    Muoncounter - "How is it possible for oceans to simultaneously absorb and emit CO2?" Actually a simple source of confusion may be the separation of natural and anthropogenic CO2 that is made the Luvenduski paper. It helps to know that net flux of CO2 into the ocean really reflects the balance between CO2 influx and outflux, just like temperature of the ocean reflects a net energy balance. So there can be a net flux of anthropogenic CO2 in (as all of it is in the atmosphere), but a net total flux of CO2 out due to local imbalances between pCO2 in water and air. It can be hard to parse that out in words without being confusing, as that text you quote makes quite clea! But fig 3 does a good job. The complex pattern of "natural" CO2 influx and outflux (Fig 3b)reflects upwelling of CO2 rich water, temp changes, downwelling (well constrained) as well as sea surface exhange and phytoplankton growth/sinking (both less well constrained) on the CO2 balance. The contemporary pattern differs in that influx of CO2 has increased regionwide due to anthorpogenic CO2. The spatial pattern of that increase is shown in Fig3c. That's the shift toward sink state I mentioned. One big unknown in all of this is if the biological pump in this region may respond to changing CO2 in this region. People are working on various aspects of that as we speak.
48. Stephen Baines at 04:22 AM on 16 December, 2010
    As for whether clouds are trickier than oceanic CO2 exchange, you'd have to say the Luvenduski paper does an outstanding job of reproducing the mesocale SST variability across the Southern Ocean (fig 2). I have pretty good confidence in their prediction of the underlying physical variables that largely constrain CO2 flux. Clouds are WAY more difficult, I think.
49. muoncounter at 05:19 AM on 16 December, 2010
    Lovenduski's Fig 4 captures in time series format the changes going on south of 35S latitude. For 'natural flux', the trend turned from - (sink) to + (source) in the mid 80s; a warming sign? But when she adds in 'anthropogenic' to create the 'net flux', the long term trend is driven downwards towards a stronger sink. Hence this patch of southern ocean is, on balance, soaking up CO2 and acidifying. But the picture changes in other parts of the world: --from Lamont Doherty --from NOAA PMEL So anyone who says 'atmospheric CO2 increase is solely due to ocean outgassing' is all wet.
50. Stephen Baines at 05:57 AM on 16 December, 2010
    Glad someone has the patience and time to post those images! "So anyone who says 'atmospheric CO2 increase is solely due to ocean outgassing' is all wet." On that we should be able to agree. Physical and chemical considerations as well the evidence from stable isotopes, physical measurements, times series of pH and pCO2 pattern/trends are in agreement and unequivocal.

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