One of my long-standing interests is the location of ocean sediment series that enable apples-to-apples comparison of the 20th century to the mid-Holocene. These are not nearly as common as one would think. Ocean sediment series covering the Holocene typically stop prior to the 20th century due to core recovery problems and, on the other hand, high-resolution series (especially from box cores) that provide detailed 20th century information are not necessarily accompanied by corresponding Holocene information (even on “intermediate” resolution.)
Last week, Sicre and coauthors archived two very high resolution alkenone series from Placentia Bay and Bonavista Bay, offshore Newfoundland (5 and 9 years respectively), covering the last two millennium, with their most recent portion dated through the 20th century. While the proximity is not ideal, the cores do appear to be close enough to three Holocene alkenone SST series from Sachs et al 2007 to compare 20th century and mid-Holocene SSTs on the North American East Coast, an exercise that I will carry out in today’s post. The exercise has some added interest because the three Sachs 2007 series were used in Marcott et al 2013 (though their recent portions were foolishly re-dated by Marcott.) As high resolution ocean SST data over the past two millennia, the new Sicre data is also relevant to the popular two-millennium reconstruction period, but the new data is about as opposite to a Hockey Stick as one can imagine. Unsurprisingly, the new data was not press released and has thus far attracted no attention.
Location Map of Sicre 2014 and Sachs 2007 Locations
The two new alkenone series from offshore Newfoundland (Bonavista Bay and Placentia Bay) are from the same authors as the high resolution Iceland MD99-2275 series. Both new series are high resolution (5 and 9 years respectively). The two new cores are located to the north three alkenone series from Sachs (2007), that were incorporated (after re-dating) into Marcott et al 2013. The three Sachs 2007 series were in the Laurentian Fan, offshore Nova Scotia and offshore Virginia, with GGC26 (Laurentian Fan) at a similar longitude to Placentia Bay but several hundred miles to the south.
Somewhat surprisingly, the alkenone SST of the more northerly series (Bonavista Bay AI07-03G) is slightly warmer than the alkenone SST of the more southerly series (Placentia Bay AI07-12G).
Figure 1. Location map showing location of three Sachs 2007 cores and the two new Sicre 2014 cores.
High Resolution Sicre 2014 Data
Here is a plot of the two high-resolution new series. Neither series shows any recognizable uptick in the 20th century. The Placentia Bay series shows a noticeable decline over the two millennia. The most recent portion of the data is from box cores the tops of which have been convincingly dated to the end of the 20th century by Pb-210 dating.
Figure 2. Alkenone SST offshore Newfoundland, from Sicre 2014 archive. Both series are splices of gravity (early) and box core (late) with a short discontinuity in each series. Red – Bonavista Bay; blue – Placentia Bay. Both samples were taken through combining gravity and box cores, with the box core results coming to the present (2006). Note the slight gap between box and gravity cores.
In a Holocene Context: Comparing to Marcott GLB
In the next graphic, I’ve compared the East Coast offshore alkenone SSTs from the Laurentian Fan and Emerald Basin cores to the Marcott GLB (red) and Northern extratropic (NXT) reconstructions (green). I’ve centered each series to have the same mean over the 0-1870 AD period (left axis has Laurentian Fan GGC26 absolute scale, while right axis is anomaly basis 0-1870 AD). The most striking aspect of the East Coast alkenone SSTs is the remarkable Holocene warmth: 4 to 8 deg C warmer than the present. Even in the alkenone data prior to Sicre 2014, the variation over the past two millennia was very small relative to the Holocene variation. Even though the Sachs 2007 was much lower resolution than the Sicre 2014 data, it also showed a non-HS decline over the past two millennia – a pattern shown more clearly in the higher resolution newer data.
Figure 2. Alkenone SST. Left panel – Holocene; right panel – most recent two millennia. Laurentian Fan (GGC26) and Emerald Basin (GGC30) compared to Marcott GLB (red) and NXT (green) reconstructions. Sicre 2014 Placentia Bay shown in blue. Note that the Placentia Bay absolute temperatures are several degrees lower than Laurentian Fan (see Appendix.)
Discussion
During the Holocene, mid-latitude and high-latitude summer insolation has decreased dramatically – by over 40 wm-2 in high latitudes. Since many, if not most, usual “proxies” respond to summer temperatures (with the invocation of annual temperatures mostly armwaving), it has long been recognized that one would expect a very pronounced signature for summer proxies on a Holocene scale. Esper et al 2012 pointed out that, even since Roman times, summer insolation at 60N has declined by ~6 wm-2 (about 1 wm-2 since medieval times), and acutely observed that one could hardly rely on tree ring “proxies” to record the smaller forcing arising from additional CO2 if they did not also record a Holocene signal – a point unfortunately not mentioned in AR5.
While summer high-latitude NH insolation has decreased sharply over the Holocene, winter high-latitude NH insolation has increased. Alkenones, as Richard Telford has recently emphasized, are responsive to summer temperature and thus the decline in East Coast alkenone SSTs since the early Holocene is to be expected. However, the size of the decline in East Coast alkenone SSTs since the Early Holocene is considerably greater than the corresponding decline in the European sector of the North Atlantic.
Sachs observed that a relatively small coastward displacement of the Gulf Stream could account for the difference and plausibly speculated that the Gulf Stream hugged the East Coast much more closely in the mid-Holocene. Even so, the differences in East Coast alkenone SST appear to be considerably higher than the SST differences in PMIP models (but this is a large topic that is outside the scope of today’s post.)
Readers need to keep in mind that SH insolation has changed more or less opposite over the Holocene – thus, at face value, the proxies ought to look a lot different in their patterns. I’ve spent a lot of time recently looking at SH Holocene proxies, but they do not appear to me to reflect summer SH insolation nearly as well as one would expect from the theory of NH proxies. But that’s a very long story.
Obviously the Sicre 2014 results provide further evidence against Marcott’s supposed early-20th century blade. At the time, I pointed out that the Marcott blade does not exist in the data and is entirely an artifact of incorrect data handling. To borrow a term from Mark Steyn, the Marcott blade was f……..flawed. It is reprehensible that Marcott and coauthors have failed to issue a corrigendum. And that specialists in the field, knowing of the error, have permitted the result to be reproduced and disseminated. While the blade in the original article may have been merely f….lawed, one could perhaps describe its promulgation as a more virulent form of the flaw. Or perhaps, to coin a word, flawed-ulent.
Defenders of Marcott have argued that, even if the uptick is flawed, this is immaterial to the Marcott estimate of the difference between Holocene and modern warmth. This is a large topic in itself – one that is made more difficult by defects in Marcott’s data analysis that are outside the scope of today’s post. In the above comparison, I’ve centered the data on the most recent two millennia (rather than 6000 years ago as in Marcott.) In my opinion, Marcott’s centering method disguises the real variation of mid-Holocene estimates and is very inappropriate for the objective of his study. But again a long topic.
But even with this limited preview, readers can readily see that the very large “residual” between the Marcott NXT estimate and the East Coast alkenone SSTs: up to 9 degrees for the Laurentian Fan SSTs. Regardless of whether this is an artifact of the proxies or a regional variation, this is the sort of thing that deserves attention. At face value, the alkenone proxies show that summer ocean temperatures along the North American East Coast between Washington and Newfoundland were 4-9 deg C warmer around 10000 BP than in the 20th century (with the larger differential to the north). In the far north, remnants of the continental ice sheet were still eroding.
In 2001, at the time of the IPCC TAR, a major report from the U.S. Global Change Program stated that the Holocene was a “relatively stable” period relative to the LGM or to the “20th century”, as, for example, the following:
Taken together [paleoclimate information from ice cores, ocean sediments etc], this information demonstrates that the Earth’s climate over the past 10,000 years has been relatively stable compared to the 10,000 years that preceded this period and compared to the 20th century.
While this statement may ultimately hold, the more that I look at Holocene data, the less obvious it seems to me. From the perspective of East Coast alkenone SST data, both the levels and rate of change in the 20th century seem unexceptional. Over the past decade, there have been many important new results from specialists in the longer Holocene period, results that, in my opinion, have been one of the most positive paleoclimate developments since AR4. For the most part, specialists in the field have attempted to understand their data, rather than throwing their data into a poorly understood black box in Mannian style, Marcott et al 2013 being an exception. Unfortunately, the many interesting Holocene results from specialists were given negligible coverage in AR5, which, instead, overfocused on diminishing returns over the past two millennia. Even worse, to the limited extent that AR5 addressed Holocene changes, it cited Marcott et al 2013, while neglecting numerous articles by more knowledgeable authors and specialists.
In addition to today’s post on East Coast alkenone series, I plan to look at other locations where high-resolution 20th century data can be compared to Holocene series used in Marcott.
Appendix
The next diagram shows the original diagram of the three alkenone series from Sachs 2007. The diagram below also shows the Virginia Slope series, not shown in my re-plot above. The horizontal axis is (obviously) in opposite direction to my diagrams.
Figure A1. From Sachs 2007 Figure 2. Alkenone-derived SSTs over the Holocene in three slope water cores. Diamonds – Virginia Slope core CH07-98-GGC19 (36 52N, 74 34W, 1049 m); open circles – Scotian Margin core OCE326-GGC30 from the Emerald Basin (43 30N, 62 8W, 250 m); and solid circles – Laurentian Fan core OCE326-GGC26 (43 29N, 54 52W, 3975 m) (solid circles).
In the figure in the post, I re-centered the Placentia Bay series to the same mean over the past two millennia as the Sachs 2007 GGC26 series. The figure below shows the two series in their (original) scale. Unsurprisingly, given its more northerly location, the Placentia Bay series is about 4-5 degrees colder than GGC26, but both series have more or less similar declines over the past two millennia. Using alkenone SSTs from Placentia Bay to project GGC26 alkenone SSTs seems like a more sensible way of trying to compare 20th century alkenone SSTs to mid-Holocene SSTs than a Marcott black box. Needless to say, one has to examine many other examples from different geographies before trying to summarize conclusions.
Figure A2. GGC26 (Sachs 2007) and Placentia Bay (Sicre 2014) alkenone SSTs.
Here is KNMI HadiSST for 47N 55W (Placentia Bay) h/t Mosher for suggestion.
Climate Audit 
42 Comments
Thanks for another concise analysis. Flawed-ulent- hilarious!
A better picture of temperatures for the entirety of the Holocene is sorely lacking.
Compare the Scotian Margin core Holocene trends (Fig A1) with the GISP2 Ice core Holocene trends in Fig5 at
http://climatesense-norpag.blogspot.com/2014/07/climate-forecasting-methods-and-cooling.html
“The earth’s orbit around the sun is not quite circular, which means that the earth is slightly closer to the sun at some times of the year than others. The closest approach of the earth to the sun is called perihelion, and it now occurs in January, making northern hemisphere winters slightly milder. This change in timing of perihelion is known as the precession of the equinoxes, and occurs on a period of 22,000 years. 11,000 years ago, perihelion occurred in July, making the seasons more severe than today.”
http://www.ncdc.noaa.gov/paleo/milankovitch.html
Don – anyone – lay person alert here; I know that there are many other cycles which affect climate, over and above Milankovitch, which I assume is the longest. Has anybody plotted these cycles against each other, synchronously as it were, and if so, what does this tell us? I’m thinking that there must be, even if thousand of years apart, a point where such cycles coincide at one extreme or the other, and how this manifests? The above suggests that we are at “optimum” Milankovitch from a climate point of view.
SteveM, as I am ever the skeptic, I would be concerned about two proximately located proxy sites converging and diverging significantly over time in proxy response – both in absolute temperature and trends. I see your intent to show proxy series in opposition to those as presented by Marcott, but I am wondering if you could make a case for using alkenone response as temperature proxies and what potential problems could exist in making this relationship.
I am ever optimistic that a proper search (from the basic physics and not after the fact selection) for reliable temperature proxies could find some even if the response was not always direct and needed adjustments. I would also think that proxies where the physical understanding is most straightforward and best understood would be the most fertile ground for those searches. Those promising ones are listed in the links below and include alkenones.
http://en.wikipedia.org/wiki/Paleothermometer
http://en.wikipedia.org/wiki/Alkenone
Kenneth wrote:
“I would be concerned about two proximately located proxy sites converging and diverging significantly over time in proxy response – both in absolute temperature and trends.”
Quite so. They are proximate but in different sedimentation regimes, so once again there are questions about whether all the variables are properly controlled. I wonder if anyone has tried taking two cores that are very proximate (like, within a quarter mile of each other)to show consistency.
Alkenones have different issues to tree rings etc. But, ultimately, they are still biological proxies where nobody really knows why they produce the amounts/ratios they do. I have certainly seen nutrient run-off from the land mentioned as a confounding factor.
A thought from the back of the room: Is it a mistake to pursue a global reconstruction? Would regional reconstructions be more accurate?
The following paper developed a regional reconstruction which could be useful to those working on attribution. I might be wrong.
On The Natural Variability of the Pre-Industrial European Climate, Bengtsson et al (2006). Here is an excerpt:
“We suggest that climate variability in Europe for the “pre-industrial” period 1500-1900 is fundamentally a consequence of internal fluctuations of the climate system.”
Click to access bengtsen06PR.pdf
Thank you for listening,
Richard
With a little research I see that Emerald Basin has been extensively cored. I was hoping to see if I could pull out some quality assurance data(core to core consistency) but too much is paywalled.
what worries me a bit is that I don’t see any MWP of LIA on these charts …
or are they that futile on a 12000 year scale ?
For these details see Figs 5,9,and 10 C D at
http://climatesense-norpag.blogspot.com/2014/07/climate-forecasting-methods-and-cooling.html
Flawed-ulent – bwahahaha!
He tawt he taw a puddy tat — but it was entirely flawed-ulent. An Elmer Fuddism at its best!
Wondering why the Emerald Basin proxy in the left-hand-side of Fig 2 has
elevated values before 11kyr BP? The three other proxies have reduced values
increasing to about 11 kyr BP and then diminishing as expected. When does
Emerald Basin realize its highest value? Very interesting data, but I am having
a hard time understanding the gigantic differences in deltaT among the proxies
for a given year in the past. Imagine being somewhere in the northern hemisphere
11 kyr BP…………in July. You are at perihelion and also the NH is tilted toward
the sun. SPF 4000 anyone?
Forgot for a moment about the top-like behaviour of the earth
about its vertical axis. It also precesses about this axis
as it makes its loop around the sun, don’t recall the rate of
this, but we can’t guarantee that maximum solar radiance will strike the NH when it is also at Perihelion. Looking again at Fig 2 above, are we not in or close to being in a transition
period for emerging from an 11 kyr slide in temperatures in the NH and then an equally start of a decline in SH temperatures. Those would tend to balance out, but if we have
many more proxies and also WX stations in the NH, wouldn’t a natural uptick in the NH data look like a systemic rise in world temperatures?
Steve,
In paragraph 5 of the discussion you forgot to note that there is an odor of flawed-ulence clinging to the Marcott paper.
“As high resolution ocean SST data over the past two millennia, the new Sicre data is also relevant to the popular two-millennium reconstruction period, but the new data is about as opposite to a Hockey Stick as one can imagine.”
The whole point of Sicre’s paper is that they chose sites that are very sensitive to movements in the Labrador Current. These are not only not coordinated with global SST, but seem to move in anti-phase. Their Fig 6, for example, emphasises how during the MWP, when alkenone SST was high near Iceland, it dropped substantially at the NE site, and less so at the SE site. Their conclusion:
“In contrast, the NE Newfoundland record shows that LC circulation is tightly linked to Arctic atmospheric conditions (NAM), which in turn modulate the advection pathway of cold, ice-loaded Polar Waters from the Arctic. This is illustrated by virtue of a generally enhanced LC during the MCA, and an overall weaker LC and likely decreased AMOC during the LIA (Lund et al., 2006). If this MCA/LIA pattern is to be considered analogous to generally warmer/colder climates in the subpolar North Atlantic, it would suggest the possibility of increasing LC strength in a future warmer climate. This would not only imply a colder future climate off eastern Canada…”
IOW, recent warming should result in cooler Newfoundland SST.
Steve: if global warming causes both warmer and cooler SSTs, almost anything can be rationalized ex post. At face value, I presume that you agree that neither the Iceland alkenone SST data nor the Newfoundland alkenone SST supports a Hockey Stick. No doubt you have ex post rationalizations, but on this simple point, it would be helpful if you clarify your agreement on this simple point so we can see whether there are any points of agreement to build on.
Second, I presume that you agree that the alkenone SST data indicates substantially warmer mid-Holocene East Coast temperatures than 20th century temperatures. Again, if you wish to argue that this is an expected theoretical outcome and provide references to authors who previously advocated this position, I’d be happy to consider your references, but in the meantime, it would be helpful to understand whether there are any points of agreement or whether you are simply indulging in shut-eyed denial.
Anti-phase, Nick?
Do you mean that if SST cools globally that the LC will warm?
“As high resolution ocean SST data over the past two millennia, the new Sicre data is also relevant to the popular two-millennium reconstruction period, but the new data is about as opposite to a Hockey Stick as one can imagine.”
The whole point of Sicre’s paper is that they chose sites that are very sensitive to movements in the Labrador Current. These are not only not coordinated with global SST, but seem to move in anti-phase. Their Fig 6, for example, emphasises how during the MWP, when alkenone SST was high near Iceland, it dropped substantially at the NE site, and less so at the SE site. Their conclusion:
“In contrast, the NE Newfoundland record shows that LC circulation is tightly linked to Arctic atmospheric conditions (NAM), which in turn modulate the advection pathway of cold, ice-loaded Polar Waters from the Arctic. This is illustrated by virtue of a generally enhanced LC during the MCA, and an overall weaker LC and likely decreased AMOC during the LIA (Lund et al., 2006). If this MCA/LIA pattern is to be considered analogous to generally warmer/colder climates in the subpolar North Atlantic, it would suggest the possibility of increasing LC strength in a future warmer climate. This would not only imply a colder future climate off eastern Canada…”
IOW, recent warming should result in cooler Newfoundland SST.
Here is Fig 6 from Sicre et al
“IOW, recent warming should result in cooler Newfoundland SST.”
a quick look at KNMI says……
guesses folks?
Here is KNMI JJAS HadiSST for 47N 55W (Placentia Bay) h/t Mosher for suggestion. Obviously they do not show the cooler Newfoundland SSTs which Stokes reported. As too often, Stokes appears to have made stuff up, rather than checking.
“IOW, recent warming should result in cooler Newfoundland SST, except when it doesn’t”
there, much better.
Steve,
“if global warming causes both warmer and cooler SSTs, almost anything can be rationalized ex post.”
I think the point Sicre et al are making is that in the region they have chosen, SST is dominated by movements of the Labrador current. Global conditions, except insofar as they influence that, play a lesser role. You pointed to remarkable Holocene warmth, which far exceeds what is generally observed elsewhere. The natural explanation is a shift from LC toward Gulf Stream conditions at that time. We know what a difference that can make; these ice-prone places are south of England.
There is no doubt, in Fig 6, that in the MWP the NE Newf site SST went down when Iceland SST went up.
Steve: I had observed in the post: “Sachs observed that a relatively small coastward displacement of the Gulf Stream could account for the difference and plausibly speculated that the Gulf Stream hugged the East Coast much more closely in the mid-Holocene.” Stokes says: “The natural explanation is a shift from LC toward Gulf Stream conditions at that time.” Once again, Stokes has presented a comment already made in the post as his own and by failing to acknowledge the observation in the post implied an error. This practice is far too characteristic of his commentary.
Nor is Stokes’ theory of a cold MWP in Labrador consistent with other information discussed here. It would also surprise Robert Way.
Gifford Miller, whose work has been discussed here on several occasions, provided convincing evidence of more-or-less synchronous MWP-LIA changes in Baffin Island and Iceland:
Perhaps Nick’s most recent spitball applies only to Placentia Bay.
As too often, Nick Stokes is in such a hurry to throw spitballs that he’s once again presenting a combination of untrue statements and/or look-squirrel.
Stokes says that Sicre et al “chose sites that are very sensitive to movements in the Labrador Current”. This is either an error or a fabrication in respect to the Placentia Bay site, used in the main comparison with Sachs et al 2007 Laurentian Fan site. While the NE Bonavista Bay site was chosen by Sicre et al to be “representative” of the Labrador Current, the SE Placentia Bay site was not so chosen. Sicre et al explicitly stated that the “SE site” (Placentia Bay) was in the “boundary zone between the Labrador Current and the Gulf Stream”. This location is somewhat to the north of the Sachs et al 2007 Laurentian Fan site, but appears to be in a location that provides information on how the 20th century alkenone SSTs would unfold in this area – as shown in the main graphic of this post. My interest – as I stated explicitly – was in comparing 20th century to Holocene data, especially as used in Marcott et al 2013, and the comparison of Placentia Bay and GGC26 seemed apt to me and still seems so. The location map in my post – taken from Sachs et al 2007 – shows and emphasizes the boundary zone to the north of the Gulf Stream along the North American East Coast and Gulf of St Lawrence. My post had reported Sachs’ theory of northward movement of the Gulf Stream in the Holocene. (In previous comments, Stokes had ignored this direct statement in the post.)
Nothing in Stokes’ comments contradicts or rebuts ANY direct statement in my post.
Stokes asserts that Sicre et al 2014 postulated an “antiphase” relationship between the NE Bonavista Bay site (in the Labrador Current) and offshore Iceland. Their discussion is based on comparing late medieval values of the Bonavista Bay alkenone SST series with MD99-2275 offshore Iceland alkenone series. There is no observable “antiphase” relationship between the Placentia Bay site and MD99-2275. So to that extent, the existence or non-existence of an “antiphase” relationship between Bonavista Bay and MD99-2275 is somewhat of a look-squirrel in relation to the comparison of Placentia Bay and GGC26. That’s not to say that it’s an uninteresting issue. I had been planning to write on the offshore Iceland alkenone SST series anyway and will address it, but Stokes’ comment does not contradict anything in the post.
And, for what it’s worth, though Stokes failed to mention it, none of the four cores: Laurentian Fan, Placentia Bay, Bonavista Bay, MD99-2275 have Hockey Stick shapes.
Steve,
Interesting post at WUWT yesterday by Willis concerning Argo. The post includes sea surface anomaly graphic. This graphic shows extraordinary warming anomaly off eastern N Am. , at about the latitude of the Gulf of St. L.
No one could explain it on that thread.
I should have added that there is an cool anomaly to the northeast of this warm anomaly in an extraordinary juxtaposition seen nowhere else on the planet.
Steven Mosher says, quoting
Nuck Stokes @ Jan 23, 2015 at 1:26 AM
“IOW, recent warming should result in cooler Newfoundland SST, except when it doesn’t”
Heh. +3. Pay attention, Nick!
“The whole point of Sicre’s paper is that they chose sites that are very sensitive to movements in the Labrador Current. These are not only not coordinated with global SST, but seem to move in anti-phase…”
Did Sicre et al make these predictions micro-climate created currents prior to his expedition or after he needed to explain his data. If there was a prior prediction was it published anywhere? If it was then in my mind the highest value of the study was to be able to independently test the validity of the Alkenone’s use as an accurate proxy. If such tests of the proxy in known micro-climates have already been done elsewhere please supply.
Steve: there are hundreds of alkenone measurements. Go to http://www.pangaea.de and search alkenone. Like any proxy, there are puzzles, but there is a great deal to recommend them relative to other “proxies”. Sicre is a she. Nor did Sicre et al purport to make such a prediction in advance.
The point of the study laid out in her application for funding? Are such applications a matter of public record? If not, I would propose they should be. No matter how well established the proxy tool I think it behooves the investigator to add to the tools value for all by making a prediction, particularly if the expectation is an anomaly in the data.
If I was funding I would require a clear point the expedition along with a prediction of findings. I would then recruit a competing expedition, preferably with different expectations, to visit the same locations concurrently, thereby ground-truthing each’s methods along with the consistency of their proxy. I would require them both to publish their data at the same hour and compare results.
“Did Sicre et al make these predictions micro-climate created currents prior to his expedition or after he needed to explain his data.”
The Sicre study here was introduced as “Important New North American East Coast Proxy Data”. Now, it appears, the conclusions are just a Stοkes spitball.
Sicre et al have been working on alkenone proxies in the N Atlantic for a long time, on various sites. The focus has been on current movements. Here is the abstract of the study
“The ice-loaded Labrador Current (LC) is an important component of the western North Atlantic circulation that influences the position and strength of the northern limb of the North Atlantic Current (NAC). This flow of cold and fresh Polar Waters originating from the Arctic has a marked impact on the North Atlantic climate, yet little is known about its variability beyond the instrumental period. In this study, we present the first sub-decadal alkenone-based 2000-year long sea-surface temperature (SST) records from the western Labrador Sea, a climatically crucial region at the boundary between the LC and the NAC. Our results show a clear link between the LC strength and the Northern Annular Mode (NAM), with a stronger NAM and a more vigorous LC during the Medieval Climate Anomaly (MCA). This suggests enhanced LC activity upon future global warming with implications for the Atlantic meridional overturning circulation (AMOC). “
Steve: Nick says: “Sicre et al have been working on alkenone proxies in the N Atlantic for a long time, on various sites. The focus has been on current movements.” WHile Sicre et al have been working on alkenone proxies for a long time, it is an error or fabrication to say that their “focus has been on current movements”. Their interest has first been in simpling collecting the data.
Further, an author’s speculation about the data is not the same thing as the data. Because the purpose of my post was the comparison of 20th century and Holocene alkenone SSTs, speculations about the connection, if any, of the Labrador Current to the Northern Annular Mode were not relevant, even if they were interesting to the authors. Nor did the authors present statistical support for their antiphase hypothesis other than a by-eye comparison over a limited period. I haven’t spent a whole lot of time on modes and oscillations as the concepts seem uninformative to me in the longer perspective of proxy studies.
It seems almost too characteristic of Stokes that he latches onto the most weakly argued speculation in a paper as the point of interest, rather than taking an interest in the data itself.
“This suggests enhanced LC activity upon future global warming with implications for the Atlantic meridional overturning circulation (AMOC).”
Sicre is speculating that warming is effecting current. Does she also acknowledge the reverse? If so, does anyone know which Sicre recognizes as the lead partner in the dance? I would expect it would oceans considering the lopsided competition in heat capacity.
I believe it is widely thought now an interruption of the Thermohaline conveyor caused a several degree global drop in temperature, taking us to the Younger Dryas minimum. Here is a known rare and significant association between climate and ocean current. Does Sicre believe that is was cooling, (from lack of CO2 or whatever,) that drove the current to stop or the reverse?
Are not ocean currents an accepted primary driver of climate fluctuation on every time scale? Are any climate scientists suggesting that CO2 is more dominant driver of global surface temp than ocean currents?
RGRAF – “Are not ocean currents an accepted primary driver of climate fluctuation on every time scale? Are any climate scientists suggesting that CO2 is more dominant driver of global surface temp than ocean currents?”
Interesting point – there is a school of thought that the accelerated warming of the 1920’s – 1930’s and 1980-1998 were amplified by the amo/pdo oscillations and the pause of the 1950-1960 and the current pause was/is dampened due to the flip side of the amo/pdo, while the overall warming trend since circa 1850 (or circa 1750 depending on which starting point you pick) has been fairly constant.
It is likely that a better understanding of the alkenone proxies may provide better insight into the issue. As Steve has noted, the alkenone proxies appear to be better/ more reliable proxies.
To see what was happening during the Holocene and beyond off the east coast of New Zealand, also using alkenones you could look at this site:
Click to access Sikes%20et%20al%2002.pdf
Notice that there is a huge jump in temperature after the
last ice age. Also, the general trend during the Holocene is
for increases temperatures, somewhat balancing out the long
temperature slide we see at the far northern latitudes.
I kind of like the alkenones.
Steve: I spend far more time looking at alkenones than any other proxy right now. Alkenone SSTs make sensible maps of both modern oceans and of deep time. However, their 20th century behavior is a real puzzle. MD97-2120 and MD97-2121 are higher resolution SH alkenone series from the same general area (also by Sachs).
Steve
Please give me your thoughts on the AR5 “estimates of internal variability” and how they relate to proxy reconstructions and projections of surface temperatures. Can alkenone reconstructions lead to improved estimates of internal variability? Or is the IPCC method of attribution flawed?
Thank you,
Richard
OT but along the Labrador Coast even though ocean currents are moving from north to south, if you attempt to sail south without the aid of an engine the prevailing summer winds in your face will provide plenty of down time.
A Viking Voyage by W.Hodding Carter provides an interesting story about the difficulty he and his crew faced trying to sail a replica Viking boat with no engine through those waters.
Reblogged this on Power To The People and commented:
New Ocean Sediment Data Shows Past Holocene Era Warmer Than Present by 4 to 8 Degrees C. “Remarkable Holocene Warmth: 4 to 8 Degrees Warmer Than The Present”.
Any thoughts on this 2009 paper?
“A —- 2,000-year-long reconstruction of sea surface temperatures (SST) from the Indo-Pacific warm pool (IPWP) suggests that temperatures in the region may have been as warm during the Medieval Warm Period as they are today.”
http://www.whoi.edu/main/news-releases/2009?tid=3622&cid=59106
My thoughts, from what I’ve read, are:
1. Tropical SST has strong correlation to global T.
2. In the tropics Mg/Ca cores are more accurate than alkenone.
It looks to me like the title of the article should be “Back to Normal.” Subtitle: The Indian Ocean has no officially recovered from the Little Ice Age.
Here is Woods Hole’s reconstruction: http://www.whoi.edu/cms/images/mediarelations/Figure2b_550_92918.jpg
Off topic, but it’s Super Bowl Sunday!
Do you know where your Gavin is?
🙂
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