Visit ArabTopics.com

More on Hvitarvatn Varves

In a previous post on PAGES2K Arctic, I pointed out that they had used the Hvitarvatn, Iceland series (PAGES2K version shown below), upside-down to the interpretation of the original authors (Miller et al), who had interpreted thick varves as evidence of the Little Ice Age. A few days ago, Miller and coauthors archived a variety of series from Hvitarvatn, prompting me to review this data.

hvitarvatn
Figure 1. PAGES2K Arctic Hvitarvatn series. PAGES2K implicitly reconstruct a Little Warm Age during the period of glacier advance, the conventional Little Ice Age.

It turns out that Hvitarvatn is a very interesting lake sediment site for a variety of reasons. It is much more securely dated than the Baffin Island sites; it has been carefully described geologically; a variety of proxies have been calculated for the location; some proxies are available through the Holocene, not just the last 1000 years or so; and, there are a variety of other well-dated proxies near Iceland.

In geophysics, specialists work out from high-quality data to lower quality data, rather than throwing all of the data into a jumble (as paleoclimatologists do). In today’s post, I’m going to parse the Hvitarvatn data, which I will later use to parse the Baffin Island and Ellesmere Island varve data, all of which has become widely used since Kaufman et al 2009 (including PAGES2K, Ljungqvist and most recently Shi et al 2013).

Dating
Varve chronologies are determined by simply counting varves – which seems straightforward enough. In Iceland, a series of well-dated volcanic tephra permit a cross-check of varve counting. When reconciled to tephra, one of the varve chronologies was over 100 years short by the medieval period. The possibility of similar errors in varve chronologies in Baffin Island and elsewhere needs to be kept firmly in mind.

Varve Thickness and Glacier Advance
A number of canonical varve sites are from proglacial lakes (e.g. Big Round, Donard and Ayr in Baffin Island; Iceberg Lake in Alaska). Like these other sites, Hvitarvatn is a proglacial lake in the watershed of the Langjökull ice cap. Miller et al observe that varve thickness is controlled by the glacier:

Varve thickness is controlled by the rate of glacial erosion and efficiency of subglacial discharge from the adjacent Langjökull ice cap.

They observe that the Langjokull ice cap had receded during the Holocene optimum and had only advanced to the lake during the last millennium. They dated the start of the Little Ice Age to ~1250AD. They dated a first phase of glacier advance between 1250 and 1500AD, with a second phase commencing ~1750AD and ending only around 1900AD. Miller et al report that, within the entire Holocene, ice-rafted debris occurred only during this second phase, especially during the 19th century.

…The largest perturbation began ca 1250 AD, signaling the onset of the Little Ice Age and the termination of three centuries of relative warmth during Medieval times. Consistent deposition of ice-rafted debris in Hvítárvatn is restricted to the last 250 years, demonstrating that Langjökull only advanced into Hvítárvatn during the coldest centuries of the Little Ice Age, beginning in the mid eighteenth century. This advance represents the glacial maximum for at least the last 3 ka, and likely since regional deglaciation 10 ka.

The two outlet glaciers terminating in Hvitarvatn, Norjurjokull and Suojurjokull, advance slowly into the lake, occupying their maximum lake area in the late 19th century, and retreat comparatively rapidly in the mid- to late 20th century.

we place the start of the LIA in the highlands in the mid-thirteenth century, when Langjökull began a series of two long periods of expansion, with high stands at ca 1500 AD and in the nineteenth century.

This study presents the first continuous record of ice cap extent for the entire Holocene and clearly demonstrates that the LIA contained the most extensive glacial advance of the Neoglacial interval. The strong multi-proxy signal at Hvítárvatn implies that the LIA was the coldest period of the last 8 ka and suggests that is unlikely for any non-surging Iceland glacier to have reached dimensions significantly larger than its LIA maximum at any time during the Holocene.

The figure below shows varve thickness and ice-rafted debris data from Hvitarvatn.

Ice-rafted debris is interpreted as evidence that the glacier had advanced into the lake. It is completely absent from the record through the Holocene Optimum and is rare until the second phase of the Little Ice Age, with maximum intensity in the 19th century with local maxima in 1940 and 1890, before declining rapidly with the 20th century recession of the glacier.

The varve record begins about 3000 BP. Varves thicken quite dramatically commencing about 1250AD, which Miller et al interpret as the start of the Little Ice Age. They interpret 1500-1760AD as a sort of standstill, with, as noted above, thick varves in the second phase (19th century) coinciding with ice-rafted debris. Varves continue to be thick during glacier recession in the 20th century, continuing to be thick into the warm 1930s.

hvitarvatn_varve-and-IRD_annotated
Figure 1. Hvitarvatn varve thickness and ice-rafted debris.

During the Holocene Thermal Maximum (HTM), the recession of the glacier meant that sediments were not varved. Miller et al utilized biogenic silica and information on diatoms to reconstruct HTM warmth, as shown below.
hvitarvatn biogenic

The Hvitarvatn data seems to provide rather secure information glacier advance and retreat, a topic of considerable importance in the older (pre-IPCC) paleoclimate literature (e.g. Matthes 1940).

Bradley and Jones 1993, an article which (rather than Mann et al 1998) did much to initiate the present programme of “multiproxy” studies, referred back to those older literature (Matthes 1940) in its introduction. They argued that records of glacier advance and retreat were compromised by the absence of continuous records and advocated instead reliance only on precisely-dated continuous records (tree rings and ice cores, but, in practice, mostly tree rings). This programme subsequently dominated the field, in part because of IPCC highlighting such studies.

At several sites (Soper Lake and Donard Lake, Baffin Island; Lower Murray Lake, Ellesmere Island), varve thickness has been said to be positively correlated with summer temperature. (Though no significant correlation between varves and temperature has been reported at similar sites: East Lake, Melville Island; Ayr Lake, Baffin Island).

PAGES2K appears to have incorporated Hvitarvatn varve thickness data into their dataset (with thick varves denoting warmth) on the basis of this practice at other Arctic sites. However, the original authors clearly interpreted thick varves as evidencing the Little Ice Age (the existence of which in Iceland is established by numerous indicators.) The PAGES2K version is clearly upside-down to this interpretation.

In an accompanying post, future post, I will compare Hvitarvatn varve thickness to varve thicknesses in the five “standard” varve thickness series used in Shi et al 2013 (and many other recent posts.)

Source: 
Climate Audit

Dear friends of this aggregator

  • Yes, I intentionally removed Newsbud from the aggregator on Mar 22.
  • Newsbud did not block the aggregator, although their editor blocked me on twitter after a comment I made to her
  • As far as I know, the only site that blocks this aggregator is Global Research. I have no idea why!!
  • Please stop recommending Newsbud and Global Research to be added to the aggregator.

Support this site

News Sources

Source Items
WWI Hidden History 51
Grayzone Project 219
Pass Blue 240
Dilyana Gaytandzhieva 16
John Pilger 416
The Real News 367
Scrutinised Minds 29
Need To Know News 2739
FEE 4827
Marine Le Pen 383
Francois Asselineau 25
Opassande 53
HAX on 5July 220
Henrik Alexandersson 981
Mohamed Omar 383
Professors Blog 10
Arg Blatte Talar 40
Angry Foreigner 18
Fritte Fritzson 12
Teologiska rummet 32
Filosofiska rummet 115
Vetenskapsradion Historia 162
Snedtänkt (Kalle Lind) 225
Les Crises 2962
Richard Falk 176
Ian Sinclair 112
SpinWatch 61
Counter Currents 10027
Kafila 502
Gail Malone 42
Transnational Foundation 221
Rick Falkvinge 95
The Duran 9971
Vanessa Beeley 143
Nina Kouprianova 9
MintPress 5680
Paul Craig Roberts 1969
News Junkie Post 58
Nomi Prins 27
Kurt Nimmo 191
Strategic Culture 5056
Sir Ken Robinson 25
Stephan Kinsella 101
Liberty Blitzkrieg 859
Sami Bedouin 65
Consortium News 2685
21 Century Wire 3655
Burning Blogger 324
Stephen Gowans 92
David D. Friedman 154
Anarchist Standard 16
The BRICS Post 1519
Tom Dispatch 543
Levant Report 18
The Saker 4462
The Barnes Review 536
John Friend 493
Psyche Truth 160
Jonathan Cook 155
New Eastern Outlook 4195
School Sucks Project 1782
Giza Death Star 1975
Andrew Gavin Marshall 15
Red Ice Radio 623
GMWatch 2375
Robert Faurisson 150
Espionage History Archive 34
Jay's Analysis 1018
Le 4ème singe 90
Jacob Cohen 210
Agora Vox 16272
Cercle Des Volontaires 438
Panamza 2238
Fairewinds 117
Project Censored 987
Spy Culture 556
Conspiracy Archive 77
Crystal Clark 11
Timothy Kelly 583
PINAC 1482
The Conscious Resistance 863
Independent Science News 81
The Anti Media 6738
Positive News 820
Brandon Martinez 30
Steven Chovanec 61
Lionel 298
The Mind renewed 445
Natural Society 2619
Yanis Varoufakis 1028
Tragedy & Hope 122
Dr. Tim Ball 114
Web of Debt 148
Porkins Policy Review 434
Conspiracy Watch 174
Eva Bartlett 618
Libyan War Truth 339
DeadLine Live 1913
Kevin Ryan 64
BSNEWS 2088
Aaron Franz 245
Traces of Reality 166
Revelations Radio News 121
Dr. Bruce Levine 150
Peter B Collins 1620
Faux Capitalism 205
Dissident Voice 11030
Climate Audit 225
Donna Laframboise 453
Judith Curry 1142
Geneva Business Insider 40
Media Monarchy 2440
Syria Report 78
Human Rights Investigation 93
Intifada (Voice of Palestine) 1685
Down With Tyranny 12269
Laura Wells Solutions 44
Video Rebel's Blog 440
Revisionist Review 485
Aletho News 21012
ضد العولمة 27
Penny for your thoughts 3091
Northerntruthseeker 2463
كساريات 37
Color Revolutions and Geopolitics 27
Stop Nato 4724
AntiWar.com Blog 3151
AntiWar.com Original Content 7095
Corbett Report 2417
Stop Imperialism 491
Land Destroyer 1222
Webster Tarpley Website 1118

Compiled Feeds

Public Lists

Title Visibility
Funny Public