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Well… hmm. The Stoat has a big hate on for the latest Hansen paper which discusses these issues, and I’m sure he’s a lot more qualified to critique it than I am (though it does seem not too well focussed/overly verbose).
OTOH, Hansen has been on the forefront of making climate change a publicly accessible issue for 35+ years now, and who can blame the man for a little (OK, a large dose of) advocacy when most of us rational sorts can see the world crumbling down all around us? Looking likely the Arctic is toast within 20 years, and that’s certainly going to affect the AMOC/global weather patterns plus speed up Greenland melting, Not looking too good from here, I’d say.
“who can blame him?” Certainly not I, and indeed I wish a lot more in similar positions would put their heads above the parapet and address the public directly.
“who can not praise him” might have been a better way to put it, if at all, particularly as much of the inevitable kickback, devoid of substance, will go for the man rather than the science.
Stoat has an axe where Hansen is concerned. He has been keeping it sharp for years. Mann? A better judge in this area, I think. He is both fairly skeptical of the paper as it goes against the mainstream and extraordinary claims require extraordinary evidence – and thinks we ignore Hansen at our peril.
From the New York Times:
Thanks for that Tamino. Watched the whole video. Jim Hansen to me comes across as very knowledgable, rational, concerned, but not at all alarmist. Not that will stop certain people claiming the latter.
Meanwhile, another American scientist, Dr Mark Eakin of the US government’s Coral Reef Watch programme, is quoted in today’s press as saying 1998 dire projections for Coral reefs under global warming “were not alarmist”. His comment, referring to a prediction of catastrophic coral reef decline, made by Australian scientist Ove Hoegh-Guldberg after 1998 bleaching events:
“What we’re seeing now is unfortunately saying that Ove’s paper was not alarmist,” said Eakin. “This year is especially telling. In the past, big bleaching events happened pretty much during the course of a year. This current bleaching event started in mid-2014.”
It seems that no let up in the bleaching equals no recovery time…
Hopefully we never get to the situation of knowing definitively that Hansen et al’s latest predictions “were not alarmist”
http://coralreefwatch.noaa.gov/satellite/index.php
http://www.theguardian.com/environment/2016/mar/22/climate-change-warnings-coral-reef-great-barrier-reef-experts-projections-scientists
Reblogged this on Anmerkungen und Beobachtungen and commented:
James Hansen ist unter den Klimawissenschaftlern einer der radikaleren und mit seinem charakteristischen Hut nicht zu verwechseln. Hier sagt er: wir haben bisher die Einmischung von Wärme in den tieferen Ozean überschätzt und die Auswirkung der Schmelzwasserschicht an der Oberfläche der polaren Ozeanbereiche unterschätzt. Wir kriegen weniger Wärmeabstrahlung ins All, stärkere Temperaturunterschiede zwischen Tropen und Polargebieten und damit stärkere Stürme und höhere Schmelzraten der Polareisgebiete als bisher angenommen.
Ah yes that reminds me….you’d called it a while back: I’ll continue to do what I can come hell or high water. Expect both” May 2011.
The shutdown of Antarctic bottom water formation that Hansen describes could explain the lack of deep ocean (> 2 km) warming observed by the GRACE satellites:
Home
though I did not see a reference to that in the Hansen paper.
And looking around their website I noticed that GRACE also observes the AMOC slowdown, a phenomenon I did not expect to see in my lifetime.
Home
Two other aspects that Jim Hansen doesn’t cover in his video, both of which certainly alarm me, concerning AMOC shutdown:
1. Oxygen transport: One of the most remarkable facts about life on Earth is this: that complex, oxygen-demanding organisms thrive in our deepest oceans, thousands of metres from the source of that oxygen: the atmosphere and the photic surface waters. They can do so because of the existence of the Atlantic meridional overturning circulation, (and similar around Antarctica) whereby oxygen-rich, saline waters sink to the ocean floor in the north Atlantic as they cool on their northward journey. It acts as the beating heart of the oceans, driving oxygen to the depths. Shutdown of AMOC means that heart falters and the ocean depths become anoxic and bacteria produce toxic hydrogen sulphide, which kills oxygen requiring organisms like fish, like … well, like almost everything really, and you end with a stinking ocean of sludge.
The kill mechanism for previous mass extinctions such as the end-Permian was ocean anoxia, euxinia and acidification, caused by rapid global warming caused by release of CO2 via extensive vulcanism. Except that now we are probably exceeding that rate of release of CO2.
2. NW Europe temperature anomaly: the paper shows temperature anomalies in the NE Atlantic, ie NW Europe in excess of -10degC from around 2065 onwards. Currently the average temperature difference between winter and summer is of a similar magnitude. Such a temperature change, making the future summers similar in temperature to present winters, would make much of the upland regions of NW Europe almost uninhabitable.
Peter Ward and Joe Kirschvink talk about these “greenhouse gas extinctions” in their new book A New History of Life. I’m only partway through it, but from what I’ve read so far I’d recommend reading it. I do hear they somewhat overstate the importance of their case in the last third of the book, but no doubt it’ll still give food for thought.
Thanks for the reference, Dan. I’ve a couple of palaeontologist Peter Ward’s previous books, Under a Green Sky (2007) and The Flooded Earth (2010) on the same subject, but it would be good to get an update. Ward also has some lectures well worth watching , eg https://www.youtube.com/watch?v=HP_Fvs48hb4
Slioch
“the paper shows temperature anomalies in the NE Atlantic, ie NW Europe in excess of -10degC from around 2065 onwards”
Now you have me really worried.
Northern Iceland has summer temperatures around 14C and winters around 4C. The agriculture is mostly based on grass; milk and dairy cattle, plus sheep.
Grass does not grow below 6C. A 10C temperature drop would render most of our agriculture impossible.
entropicman
Until I hear otherwise, I will assume that pasture-fed ruminants are terrible for the climate. They produce lots of methane and take up land that could be used for other uses e.g. growing trees or even growing biomass for BECCS (or if BECCS is too hard sinking the biomass in the ocean.)
I just don’t see how a cow roaming around producing 100 kgs of methane a year can be good for the climate. Depending on what measure is used hat might convert into 10 tonnes CO2e per cow per year.
Are the claims I read about grass fed cattle having little impact on climate just another green fig leaf for our damaging way of life?
Tamino, thanks for passing this worrisome video along… I think.
Tangentially relevant–
Commenter ‘Theo’ asked what I consider a pretty good question on RC about why the winter and summer phases of the DMI ‘north of 80’ temperature graph look so different. In the course of responding to his question (I consider myself a charter member of the RC ‘fools rush in’ club), I wrote:
Occurred to me that it’d be nice statistically-oriented blog post for someone to do seasonal bins for the DMI data and compare those trends. The differences are very obvious to the eye, as Theo found, so I think one would likely find some strong statistical differences. Of course, it’s based on reanalysis data, which isn’t necessarily the best for climatic purposes due to inhomogeneities (and IIRC, DMI data isn’t based on the same reanalysis over the entire span.) Still, it might be a) interesting, and b) illustrative as hell.
So I’m throwing this idea out there, since this site is pretty much a hot-bed of data/stats enthusiasts, quite a few of whom do blog. Does that idea pique anyone’s interest?
(I’m not well-equipped to do the analysis myself–I might be just able, but would be error-prone and it would take me forever. However, I would be interested to write up/re-blog any results.)
[Response: Hasn’t DMI changed their model over time, so that previous data aren’t congruent with recent data?]
Inline: “[Response: Hasn’t DMI changed their model over time, so that previous data aren’t congruent with recent data?]”
Yes, I think so, so a rigorous analysis would need to consider that. IIRC, they transitioned from an earlier, less-sophisticated reanalysis product to a better one. It’s documented, as I recall, on their site. I’m not sure what even a close order estimate of the quantitative bias would be, nor if there is a reasonably efficient way to compensate.
OK. Still not a lot of time, but I’ll take a quick look at the DMI site…
It’s here:
http://ocean.dmi.dk/arctic/meant80n.uk.php
Description:
So, tabulating:
1958-2002: ERA40
2002-2006: NWP T511
2006-2010: (NWP, I presume) T799
2010-: T1279
Ouch. Starting to remind me of the satellite temp record.
Assuming I have your query right, Doc:
I emailed DMI some years about the relatively stable summer temps north of 80 and the bigger swings and warming trend of winter. The response was pretty straightforward. North of 80 mostly has sea ice year-round (so far), so surface temps are clipped at close to 0C. But sub-zero temps during Winter are way below the clip and can warm.
Dunno about any recent model changes. That was the information I got maybe 5 years ago.
Yes, that’s more or less what I told Theo.
Found where I posted a copy of the email reply from DMI (Steve Goddard’s site).
https://stevengoddard.wordpress.com/2010/09/21/albedo-feedback-in-the-arctic/#comment-2442
Interesting… thx.
I found this disturbing bit on Wunderground today. Note that it says if we act to decarbonize now, this need not happen.
http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=3269
Lloyds of London comissioned the report, UK/US S Task Force on Resilience of the Global Food Supply Chain to Extreme Events supported it, the model upon which it was based was developed at Anglia Ruskin University’s Global Sustainability Institute, and Lloyds released it in June of 2015. For those who are interested, a copy is available here:
Click to access food%20system%20shock_june%202015.pdf
Slioch:
Since oceans are wind and tidally mixed, i.e., heated from above and need to be stirred to mix dense waters back to the surface, there is always a possibility that the flow of oxygen to the abyss may be disrupted. However, the reduction of NADW formation in the North Atlantic is balanced by increased winds around Antarctica to drive southern ocean deep water formation.
It is very difficult to drive the oceans anoxic. For example at the last big temperature excursion driven by greenhouse gases, the Paleocene-Eocene thermal maximum, the deep circulation wasn’t disrupted despite release of 2000 to 5000 Gt C. Right now we are at about 500 Gt C release.
Mitch,
I wouldn’t get too carried away with a PETM-AGW emissions comparisons without first adjusting them for the different situations. The 500+Gt(C) (&rising) AGW emissions have happened far quicker than the PETM emissions, so peak airborne fraction will be far lower in the PETM. Also the initial CO2 levels of the Paleocene were higher than our pre-industrial levels, although the PETM figure isn’t known with much precision. If you take those two factors into account, and the range of PETM emissions (2,000 – 7,000Gt(C)) found in the literature, the effective PETM comparison emissions can easily drop to worryingly low levels. If Af is 1.5 higher today (43% AGW, 30%? PETM) and CO2(initial) approaching 4x lower (275ppm AGW, 1,000ppm? PETM), the comparison yields 330Gt(C) to 1,170Gt(C) PETM(effective) against 560Gt(C)+120Gt(C)/decade-continued-emissions.
And the disruption to the AMOC discussed by Hansen is not comparable to PETM as it was an ice-free world back then.
Mitch, The ocean’s mixed layer is only a few hundred meters deep. Below the thermocline, there’s very little mixing and the ocean’s average depth is 3,688 m. The deepest waters in the Atlantic are sourced from the THC sinking around the Antarctic and above those waters is that from the sinking in the high latitude North Atlantic. The sinking is said to be the result of increased salt concentration as a result of the yearly formation of sea-ice, both around the Antarctic and in the Arctic Mediterranean (aka, the Nordic Seas) plus the Labrador Sea. The fact that the waters below the thermocline are near freezing indicates to me that there’s little vertical mixing in other areas of the Atlantic. In the Equatorial Pacific, the easterly trade winds tend to bring colder waters to the surface as a function of the ENSO process.
Graph was selected from:
http://sam.ucsd.edu/vertical_sections/Atlantic.html
Here are some for the Pacific:
These are from: http://sam.ucsd.edu/vertical_sections/WHP_Pacific_public.html
One of the standard models that the group used, treats CH4 as having a short atmospheric half-life. However, for the last 25 years, CH4 atmospheric concentrations have increased year over year, and forcing from CH4 has increased. Thus, the model may not fully capture actual observed forcing to date or appropriately model future forcing. We may be farther along the path to AGW than the paper suggests.
All in all, I expect to see weather over the next 30 years include scenarios that paper projects for the period 2060 – 2080.
In particular, I would be very surprised if sea level rise is not much greater than suggested by the paper.
One sentence in the paper suggests that the group is thinking in terms of sea level rise as a result of ice sheet melt in situ as a result of energy from forcing. However, as ice warms, it weakens and is subject to fracture and debris flows driven from its own potential energy. This reduces the energy required to produce SLR by orders of magnitude, and thus SLR may occur rather abruptly and sooner, rather than later.
AGW is like termites and dry rot. It is cheaper to fix it sooner, rather than later.
Your Loyal Alarmist.
Interestingly, there is a similar process in Plate Tectonics – orogenic collapse. Basically, if you pile up a big enough mountain range/plateau, like Tibet, it slides out sideways and collapses due to gravitational instability. And we see that Tibet is actually undergoing extensional faulting right now.
A similar process could demolish ice sheets that are grounded below sea level very rapidly; as the melting front moves to deeper water, the remaining ice sheet becomes unstable and collapses to a thinner, and grounded state in a very rapid process.
I like Hansen, especially for when he says things like he expects to be called to testify against the CEOs of fossil fuel companies when they are on trial for crimes against humanity.
I don’t know what to make of this latest paper.
Hansen once made a prediction, in his Bjerknes lecture no less, that if humanity attempted to burn all the fossil fuels a Venus syndrome would occur, i.e. the oceans would boil away and life on Earth would end. He couldn’t model it: “Our model blows up before the oceans boil, but it suggests that perhaps runaway conditions could occur with added forcing as small as 10-20 W/m2” Nevertheless, he maintained, try to burn all the fossil fuels, and ocean boiling is a “dead certainty”.
Recently, Hansen has walked back that claim as the result of using a more realistic model:
Still, it would appear that we have it within our power to make the Earth largely uninhabitable for multicellular life. But personally I doubt that we could ever get that far. We would in all likelihood destroy industrial civilization well before that. However, with the current business as usual trajectory which Paris has yet to affect, it is largely thought that we may achieve 4°C within this century, and it is largely thought that this is incompatible with a globally organized civilization.
According to Kevin Anderson of the Tyndall Institute:
CORRECTION: I was trying to cut as much of what I thought nonessential from my Hansen quote but trimmed a little too much at the beginning of the second paragraph where he states, “One implication is that if we should ‘succeed’ in digging up and burning all fossil fuels,
some parts of the planet would become literally uninhabitable, with some time in the year having wet bulb temperature exceeding 35°C.” Only some parts achieve a wet bulb temperature of 35°C, but in his view the rest of the world would still be hot enough that it would likely end of our species – as indicated by the rest of the paragraph.
Is there a substitute for AMOC? Or is that pathway a unique bit of geography?
Will the lack of a route for warm water to the north have an effect on Arctic melt?
It seems to me that an AMOC shutdown might lead to a large split in temps. A much hotter equatorial band and much cooler northern temps. What am I missing in my off-the-cuff understanding of the issue?
Read Hansen’s paper. There is a reason Archer was so complimentary, and it has nothing to do with the alarm content. In most blog presentations of a possible shutdown of the AMOC, the earth gets very cold for a very long time. Read Wally Broecker for a reference source. In the Hansen paper, there is a surprise for the koldies. Same one as ever… ACO2 and science.
JHC,
Cold for a long time??? The SH becomes warmer if AMOC is shutdown, the NH gets much colder, in a hosing event (means the AMOC is not allowed to recover what is not realistic), there would be only reduce Temperature for some decades but then after would increase temperature by GHGs with a shutdown AMOC, in Realitiy the AMOC would beginn slow to recover, so then its more likely, that 1) Temperature would be stalled for some decades and then would more intense increase by recover of AMOC and increased GHGs.
See this Paper here: http://www.nature.com/articles/srep14877 (but think about its a hosing scenario)
Eric Swanson–
Ocean mixing is misunderstood, and often misrepresented. Surface waters going down into the oceans are driven by how fast water is being pumped up by tidal and wind mixing. As the figures you present show, wind mixing is relatively inefficient and only efficiently mixes the upper 400 to 500 m of the oceans. Density change only drives the relative proportions of different water masses that go down. When NADW becomes too buoyant to become a deep water mass by addition of fresh water, that water is replaced by additional Antarctic bottom water.
So, the deep ocean doesn’t become stagnant, it just gets replenished from the south. And, the heat that had been going to the North Atlantic now switches to the Antarctic. This is known as the “polar see-saw”.
Mitch, When you wrote: “NADW becomes too buoyant to become a deep water mass …”, I think you should be referring to the surface waters in the high latitude North Atlantic, not the deep waters, which are already way below the surface and thus not impacted by low density melt water at the surface. What happens, as I understand it, is that the sea-ice freezing process releases salt into the surrounding surface water. That water is actually less salty than that of the NA sub tropical gyre, the result of precipitation and the seasonal melt of sea-ice. The waters which have been found to sink in the Nordic Seas or in the Arctic end up in the Arctic Mediterranean, the basin below the sill depth of the Greenland-Iceland-Scotland ridge. Any water sinking into that basin must displace some waters which then flows over the sill, these waters sink to become the NADW. Along the way down, the salty AM water partially mixes with other NA water, which results in lower salinity for the NADW compared with that from the AM. The THC sinking is impacted by freshening of the surface water, as seen in historical freshening events, such as “The Great Salinity Anomaly”.
The problem with melting ice from Greenland is that the amount of fresh water added into the ocean would be both large and the addition could last many years, with long term consequences not seen in historical times. I’m still reading Hansen et al., but I haven’t seen a reference to what may happen in the AM as Arctic sea-ice continues to decline and more open water will allow wind driven currents to move warmer waters into the Arctic. This might be seen in the Barents and Kara Seas as an extension of the Norwegian Current flow, then feeding into the newly opened North East Passage to the North of Siberia. I think there are many details still to be worked out.
for Andrew Dodds, in case you wanted a cite for that possibility, here’s one:
Diverse calving patterns linked to glacier geometry
Nature Geoscience (2013)
doi:10.1038/ngeo1887
“Here we present a numerical model that simulates the disparate calving regimes …. Our model treats glacier ice as a granular material made of interacting boulders of ice that are bonded together. Simulations suggest that different calving regimes are controlled by glacier geometry, which controls the stress state within the glacier. We also find that calving is a two-stage process that requires both ice fracture and transport of detached icebergs away from the calving front. We suggest that, as a result, rapid iceberg discharge is possible in regions where highly crevassed glaciers are grounded deep beneath sea level, indicating portions of Greenland and Antarctica that may be vulnerable to rapid ice loss through catastrophic disintegration.”
Eric:
Adding fresh water to the North Atlantic means that it becomes less dense than it is now in wintertime. Antarctic Bottom water is significantly more dense, even today because of low fresh water input and major freeze exclusion of salt being added as sea ice forms. Studies of the last glacial maximum show that the water out formed in the Greenland-Iceland-Norwegian (GIN) Seas became less dense, and circulated out at 1500 m rather than 3500-4000 m as they do today. The deep North Atlantic was filled with Antarctic water. The Antarctic water circulates back to the surface around Antarctica.
Studies have been done of temperature change under continued greenhouse gas emissions while ‘hosing’ the GIN seas with fresh water. The result is still warming in Europe, just less warming than in North America. The excess heat is transferred to Antarctica.
Mitch, you are mixing apples and oranges. The issue has nothing to do with the AMOC during glacial conditions, as those conditions don’t apply in our world situation. Hansen’s paper noted Rahmstrof’s (1994) finding that the sinking during glacial times shifted to the south of the GIS ridge, but that isn’t today’s problem. Adding fresh water to the sub-polar gyre and/or the Greenland Sea says nothing about what changes will occur to the north in the Eastern Arctic Ocean.
It sounds like you are using Seager, Battisti et al. (2003) as your reference, a study in which the sea-ice was proscribed, thus could not respond to the local change in climate and thus understated both the feedback and the resulting cooling after a hosing. If not, which more recent studies(s) do you prefer? Recall also that Hansen’s latest model used a rather coarse ocean model (resolution of 4×5 deg and 13 layers that increase in thickness with depth), which might not capture the full effects of sea-ice and ocean circulation. As Hansen notes: “Another flaw is unrealistic hemispheric sea ice, with too much sea ice in the Northern Hemisphere and too little in the Southern Hemisphere.” All righty, then…
He (Hansen) was just on our local (New Zealand wide) radio interview show. Kim Hill is well regarded and does a really good interview – It may be Saturday here but it was Good Friday wherever Hansen is… and he did it.
http://www.radionz.co.nz/national/programmes/saturday
Eric:
Let’s go back to the original point–whether an AMOC collapse would cause ocean anoxia–there is no evidence in models or paleoceanographic data that AMOC shut down would cause anoxia. Second, if AMOC shut down, deep circulation would be replaced by Antarctic deep water formation, because deep water is pumped up, not pushed down. Abyssal ocean circulation is not thermodynamic.
Finally, AMOC tends to be overblown on blogs. Collapse of AMOC leads only temporarily to global cooling. Modeling over the years shows that it reduces global warming over Europe primarily. The latest paper that I have found suggests a 15-20 year global cooling if there is a complete AMOC collapse but is then followed by continued warming (Drijfhout, 2015, Sci Repts, available here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4594299/). However, most models show linear decrease of AMOC with warming, not collapse.
Mitch, where did I mention a total AMOC collapse causing anoxia? And, FYI, the deep water is pulled down, not pumped, by gravity as the water with the greatest density sinks to the bottom.
Note that Drijfhout’s work uses the ECHAM5/MPIOM model and their study applies “a freshwater anomaly of 1 Sv (Sverdrup = 106 m3 s−1) between 50°N and 70°N in the Atlantic”. Is that hosing a realistic representation of melting around Greenland? The East Greenland Current would move any melt water toward the southern end of Greenland and melting on the western side of Greenland would likely pass thry the Baffin Bay/Davis Strait into the Labrador Sea. And, again I ask, what happens to the sea-ice, particularly over the Arctic Ocean? Hard to tell from what’s written, since there’s no description of the sea-ice model used which I could find in the open literature.
Click to access Poster_LAURIAN_NCAR.pdf
Eric,
“…again I ask, what happens to the sea-ice, particularly over the Arctic Ocean?”
By far the greatest component of winter recession of sea ice is in the seas bordering the Atlantic (Kara, Barents, Greenland Seas). This suggests a strong role for ocean driven warming impact on the ice edge in winter. Note that if one were to naively expect atmospheric warming were the cause of the winter retreat, then at that same simplistic level one might presume recession as being equal around the northern hemisphere. This is not happening.
However the water advected northwards in the Atlantic is saline and dense, so as it enters the Arctic Ocean Basin it falls away from contact with the surface sea ice. This happens around the eastward lip of the Eurasian Basin.
This falling away creates a warm Atlantic water layer deep below the sea ice, ITP data is available here: http://imb.erdc.dren.mil/buoysum.htm
A typical temp/salinity plot is seen here: http://www.whoi.edu/itp/images/itp79dat3.jpg
Note the deep warm layer in panel 2.
The implications of a large freshwater pulse from Greenland are hard to call.
Currents driven by deep subduction off Greenland may be cut off, which may remove a source of warmth to the Arctic Ocean. However general surface salinity of the North Atlantic is much higher than for Pacific waters drawn in through the Bering Strait, this is the case even well away from Greenland.
And this water is not advected into the region by processes that would be affected by Greenland (surface winds and Ekman pumping play a role here).
So it is possible that the salinty of the North Atlantic could be diluted reducing the depth of formation of deep Atlantic Water within the Arctic Ocean Basin, with North Atlantic warmth playing a more active role in reducing sea ice thickening within the Arctic Ocean Basin. Sea ice forms due to the heat flux from ocean to atmosphere in the cold of the Arctic Ocean. As heat is drawn from the ice/ocean boundary at the underside of the ice pack new ice accretes to the underside of the ice this is the dominant process of ice mass growth in winter. If one adds in a source of heat under the ice then this essentially subtracts from the heat flux that causes growth of ice and results in thinner peak thickness of winter sea ice. The result of this is more aggressive spring melt and faster summer recession of the ice edge leading to lower summer extent as seen in the PIOMAS thinning experiment carried out for Ed Blanchard Wrigglesworth.
In the following figure from that experiment, the left panel shows recent conditions, the right panel shows recent year’s weather with the entire pack thinned by 1m in May. Months go down, June, July etc
This is an argument from the extreme, I am certainly not expecting this to happen over the next decade. However it does show how important initial thickness is in the summer melt.
Chris, thanks for the long reply, which rather illustrates my concerns.
As your link to the graphs of temperature and salinity data indicate, the deepest waters of the Arctic Mediterranean have a high salt content and low temperature, the result of centuries of THC sinking. The bottom panel of your ITP79 graph shows salinity above 34.85, while your map of surface salinity shows the Norwegian current at or above 35. Those waters above the Barents Shelf could rather easily sink and add to the overflow at the Denmark Strait sill, even if the sinking of lower salinity waters in the Greenland and/or Iceland Seas were suppressed by melt water from Greenland’s glaciers. Here’s an interesting presentation:
Click to access 03_highres_Chassignet.pdf
Hansen’s paper claims that their model produced too much sea-ice, whereas we are now seeing considerable loss of sea-ice at the end of the melt season. Furthermore, we now observe sea-ice at the end of the freeze season that presents a large increase in the fraction of first year ice, which is thinner and is more easily melted in the subsequent warm season because the thickness is reduced. There’s THC sinking which has been found in the Arctic, as well as in Greenland and Iceland Seas, thus my concern regarding Hansen et al. in which they project reduced AMOC while not specifying what will happen to the sea-ice, starting with recent historical trends.
Eric,
I think your concerns are sound. I’m fairly well read but may have missed something. That noted…
I haven’t read any studies that use the current state (Greenland run off, AMOC state, sea ice state – we now have a largely first year ice pack!) as initial conditions then proceed forward. Due to the importance of what we’re seeing now I think that casts all the projections I’ve read of in rather more uncertainty than I am happy with (for myself to rely on them). Given the impacts of loss of sea ice on the atmosphere and weather that’s already observed, that casts some further uncertainty on regional projections.
PS – I should add to the previous post. It might be presumed that loss of sea ice is being driven by ocean warming being advected from the north Atlantic and that as a result a decline in the AMOC will result in a sustained survival of sea ice. I am not persuaded at all by this, it’s a factor but not a leading one. I am persuaded by the proposition of Lindsay & Zhang, as explained in this blog post.
http://dosbat.blogspot.co.uk/2014/03/what-caused-volume-loss-in-piomas.html
The decline in extent being a result of the increase in open water formation efficiency resulting from the loss of volume.
Chris, I suppose that you’ve seen this animation of the progression from old to new sea-ice:
When I first saw an earlier single year annimation, I realized that the sea-ice which we see in single images along East Greenland is actually ice which is moving along with the East Greenland Current after export thru the Fram Strait. The animation appears to agree with Maslowski’s work, as it shows a flow which brings warmer water into the Arctic thru the Bering Strait:
Click to access maslowski.pdf
Also FYI, here’s a discussion from RealClimate back in 2005 about Peter Wadhams and his notion of THC sinking via “Convective Chimneys”:
http://www.realclimate.org/index.php/archives/2005/05/gulf-stream-slowdown/
Needless to say, it’s a very complicated problem…
Eric,
That’s wind driven movement. The Beaufort High is anticylonic (clockwise winds). Strong wind flow from Banks Island over the pack (Beaufort towards Chukchi) causes mass fracturing events across Beaufort.
The AO index also plays a role., when the AO is negative anticyclonic (clockwise) winds dominate across the pack causing a mass clockwise movement of the pack. This stalls with a weak AO index, even reverses with a positive AO index. The effect in a slide show of ASCAT stills is rather breathtaking – the pack seems to move like a living thing.
A few days ago, I spoke to two climate people from the UK Met Office Hadley Centre where they do the UK’s climate research. Neither knew about this latest paper by James Hansen.
One, who was a climate modeller, did not know about the cooling patch in the North Atlantic – but he had of “the hot blob” in the Pacific. He also said that Hurricane Sandy was not unprecedented – it’s just that it happened to hit a densely populated area.
Is this worrying?
Reblogged this on Don't look now and commented:
Could super storms overwhelm the sea defences around nuclear power stations? (http://ow.ly/ZXYLP )
At Turkey Point in Miami a super storm will not be necessary. Sea level rise of 2 more meters will submerge the roads leading to the plant. A category 4 or 5 hurricane right now would have a chance of overwhelming their defenses.
Hmm, I see what you mean:
Picture:
http://www.trbimg.com/img-547f824c/turbine/fl-turkey-point-reactor-20141203
Opposition to nuclear expansion:
http://www.miamiherald.com/news/local/community/miami-dade/article18627960.html
Overview of facility:
https://en.wikipedia.org/wiki/Turkey_Point_Nuclear_Generating_Station
Yeah, what could possibly go wrong?
The Climate Central map located here: http://ss2.climatecentral.org/#13/25.4541/-80.3310?show=satellite&projections=1-RCP85-SLR&level=3&unit=feet&pois=hide shows Turkey Point as an isolated island after only 3 feet of sea level rise. It appears to be about 2-3 miles to dry land. How could a reactor survive as an island to itself?
The Climate Central map uses surveyed land heights. Many other similar maps on line use NASA data that shows sea level rise compared to the top of trees and the roofs of buildings.
geoff, that’s kind of what happened at Fukushima Dai. Tsunami rather than a superstorm, but same principle.
From Ocean Explorer, NOAA (http://ow.ly/10amxQ )