Comments on: Loso: Varves in Alaska

By: Loso: Varve Thickness and Nearest Inlet « Climate Audit

Loso: Varve Thickness and Nearest Inlet « Climate Audit — Tue, 28 Jun 2011 01:38:22 +0000

[...] varve thickness at Iceberg Lake was suggested by Willis Eschenbach at Climate Audit two years ago here: My own feeling is that the dropping of the lake level in 1957 is the key to the greatly elevated [...]

By: Steve McIntyre

Steve McIntyre — Fri, 04 Sep 2009 13:24:52 +0000

The data at NCDC now says:

Master chronology is updated to correct an error in Loso et al. (2006),
and presents simple averages of data from individual sections.

There is no reconciliation statement however. Willis noted above that he got data from Loso at the time; it would be worth comparing the two versions to see what was “corrected”.

By: Steve Sadlov

Steve Sadlov — Wed, 25 Apr 2007 15:38:17 +0000

A serious effort need to be made to monitor and study the negative PDO phase we now seem to be in. The last one was unknown, since the mechanism was unknown during the period from the late 1930s to the late 1970s. It is both exciting and – well – alarming – to be living in these times. There will be a real mixed bag. To my fellow southwesterners, I can only say, the marginal drought of the past few years is likely to spread to encompass the whole of the former Mexican territories – from the border to 42 north, from the sea to the high plains east of the Front Range. Dixie will also very likely be in a bad way. The rest of the country will encounter cold and wet conditions. Another “year with out a summer” ala 1814, but by different means, cannot be ruled out, for the Midwest and Northeast at one or more points during this phase. The resulting highly zonal jet stream (as opposed to the past 30 + years’ wavy patterns) may also bring shocking changes to Europe, who have been lulled by abnormally benign conditions especially since the late 1980s. Granted, there were a few cold winters (or to be fair, portions of winters) there, but by and large the pattern has been mild for them. Interestingly, a previous likely time of negative PDO likely commenced during the Victorian Era and ended during the final days of World War One. Accounts from that war clearly depict a much more snowy climate very near the coasts of the English Channel and North Sea, than what has been experienced since the 1970s there. Also, of interest, is the fact that the most recent PDO commenced not long before Operation Barbarossa – the rest, as they say, is history.

By: DougM

DougM — Wed, 25 Apr 2007 15:12:47 +0000

Thicker varves would seem to be a logical result during periods of glacial advance and maximum glacial extent. During these times the speed of the ice in the glacier would likey be above average resulting in increased erosion. At the farthest advance, the area of erosion is also at a maximum. The increase in erosion should produce greater average deposition rates. Advancing glaciers may produce tempoary increases in available materials as they overrun previous terminal moraines.

By: Roger Dueck

Roger Dueck — Tue, 24 Apr 2007 20:05:06 +0000

The Holocene, Vol. 16, No. 5, 705-716 (2006)
DOI: 10.1191/0959683606hl965rp
⧠2006 SAGE Publications

Pattern and timing of sediment infill at glacier-fed Mud Lake: implications for lateglacial and Holocene environments in the Monashee Mountain region of British Columbia, Canada
K. R. Hodder
Department of Geography, Queen’s University, Kingston, Ontario K7L 3N6, Canada, kr.hodder@utoronto.ca

J. R. Desloges

Department of Geography, University of Toronto, Toronto, Ontario M5S 3G3, Canada

R. Gilbert

Department of Geography, Queen’s University, Kingston, Ontario K7L 3N6, Canada

The Holocene sedimentary infill of proglacial Mud Lake, British Columbia, Canada, was investigated using 3.5 kHz acoustic sub-bottom profiling and sediment samples. The sediment infill is a mixture of silt and clay and is divided into five stratigraphic units: massive silt (Unit 1), weakly laminated silt with very fine sand beds (Unit 2), weakly laminated silt with rippled beds of fine sand (Unit 3), weakly laminated clay with very fine sand laminations (Unit 4) and silt-clay varves (Unit 5). Acoustic reflectors correlate with stratigraphic unit boundaries. Annual accumulation rates were estimated for six age/depth intervals: prior to 9.6 kyr cal. BP, accumulation rates were very high – on the order of several centimetres per year. Early to middle Holocene sediment inputs (9.6-3.6 kyr cal. BP) were variable but low, ranging from 0.3 mm/yr to 1.2 mm/yr. The late Holocene (most recent 3.6 kyr) shows annual accumulation rates that generally exceed 2 mm/yr. Surface sediment reveals a mean of 4.3 mm/yr over the last 20 years. These results are consistent with regional Holocene chronologies and long-term paraglacial succession: (1) maximum sediment and meltwater availability and minimum stabilization by vegetation following Fraser deglaciation replaced by (2) less meltwater and sediment availability during the Hypsithermal, and (3) more stabilized sediment during the early and mid Holocene. Renewal of glacial activity, particularly in the late Neoglacial, has led to increased rates of accumulation in Mud Lake. Despite the contrasting geologic setting of Mud Lake in the Omineca belt, contemporary sediment yield is consistent with the trend of sediment yield with glacier cover in lakes of the adjacent Foreland belt.

I have not read this paper but the conclusions seem consistent with Willis’ and my position on Iceberg Lake varves. Interesting in that the increased rates of sedimentation are during periods of increased glaciation.

By: Steve Sadlov

Steve Sadlov — Tue, 24 Apr 2007 19:07:59 +0000

RE: #13 – In fact, SE Alaska is what I would consider the global type location for PDO effects.

By: Willis Eschenbach

Willis Eschenbach — Tue, 24 Apr 2007 18:23:31 +0000

Dear mccall and Lee, could you please take your dispute elsewhere? This thread is about Iceberg Lake.

Many thanks,

By: Willis Eschenbach

Willis Eschenbach — Tue, 24 Apr 2007 04:09:25 +0000

Lee, thanks for your post. As I showed in my graph, the 95% CI is very wide. But even ignoring that, the trend 1958 – 1998 is not significant.

In addition, the similarity with temperature is only superficial. I have looked at the correlation of the varves with the local temperature records (Yakutat, etc. listed above). There is no statistically significant correlation with either the full records, or the summer (May – October) temperatures.

You say:

3. willis’ corections to the 20th century part put the graph EVEN MORE into line with a scenario of warming in the latter 20th century, and a late 20th century warmer than the “MWP,” assuming varve thickness is a proxy for temperature.

To draw that conclusion, you’d first need to show that it is a proxy for temperature. I have found no evidence to date that it is, and much evidence that it is not. For example, it shows the temperature peaking in about 1925, and dropping until about 1945, when in fact the temperatures were going strongly the other direction.

The data for 1958 is flagged as “earthquake” in the data files, because of the huge shaking from the 1958 earthquake. In addition, in 1957 the lake shape changed radically, bring the inflow much closer to the location of the cores, as well as reducing the volume. My feeling is that these events are related the change in the record after that.

By: Lee

Lee — Mon, 23 Apr 2007 23:24:22 +0000

DaveB, this is why I specifically said I was eyeballing. I attempted to be careful in pointing out interesting features, and NOT claiming that anything about that was definitive, precisely because of the noise in this one record. But those are interesting features, and it would be interesting to see if they are mirrored in other kinds of proxy or historical data. And it is also interesting that willis’ claimed corrected analysis make the record more closely mirror the probable historical record and recent warming, rather than less.

If this graphic was the only datum, it would be meaningless. But it is not the only datum – there is a generally good existing picture of a MWP, followed by a LIA, followed by recent warming, and this data follows that picture very well. It is fully consistent with that story – while it cant be statistically distinguished in this one record, the fact that it tracks with expected results so well lends credence to the idea that the average trace is reasonably close to reality. It would be interesting to see this one analysis combined with similar analyses from this and other proxies in a multiproxy analysis using something different from dendro records.

The recent qualitative change (the glacial floods) and perhaps the possibly-real qualitative difference in the modern minimum thickness varve frequency, lend support to the idea that something in recent years is different from the rest of the record.

By: Dave B

Dave B — Mon, 23 Apr 2007 21:23:08 +0000

lee,

willis certainly does not need me to defend him, but perhaps you didn’t “eyeball” willis’ “discussion”:

“Because of the width of the CI, none of these data points is significantly different from any other of these data points. As a result, there’s not much we can say about the trends or the values.”

eyeballing this graph is like eyeballing a straight line, WRT MWP, LIA, or modern warming.