The Chronology and Stratigraphy of the Little Ice Age Presented by Sara Peek November 27, 2006.

The Chronology and Stratigraphy of the Little Ice Age

Presented by Sara Peek

November 27, 2006

Overview Background Use of dendrochronology and

lichenometry to date coarse warming Varved sediments provide a more

continuous climate record Ice core records imply a worldwide

event

Background What is the Little Ice Age?

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.



Possible Causes Reduced solar intensity

14C and 10Be, as well as medieval sunspot counting, proxy for solar intensity


are needed to see this picture. QuickTime™ and aTIFF (LZW) decompressor


Possible Causes Increased volcanic activity

Ash clouds block solar radiation; some cooling can persist for 2 years after the eruption

Sulfuric acid in the stratosphere can also reflect sunlight, resulting in further cooling.

Warming Did the Little Ice Age end because of

the Industrial Revolution?






event

Dendrochronology & Lichenometry





Annual tree rings vary in thickness

Lichen Rhizocarpon geographicum increases in radius over time

Dendrochronology & Lichenometry

Objective: Date moraines, which can be a proxy for climate shift, associated with the Little Ice Age

Methods: Counting tree rings and measuring lichen radii



The moraine complex is (i) two inner, relatively barren, fresh-appearing moraines (Moraines 1–2), the second of which (Moraine 2) is considerably larger and overrides the proximal face of Moraine 3; (ii) a middle suite of three sparsely lichen and tree-covered moraines (Moraines 3–5), with the outermost of the three (Moraine 5) being the most prominent; and, (iii) an outer suite of three smaller, forested moraines (Moraines 6–8).

Colonel Foster Glacier



Septimus Glacier





Results

The year associated with each moraine denotes the year that the glacier began to recede; that is, years that climate was warming.




event

The Varved Sediments of Donard Lake

Donard Lake is located in a trough of the global-scale west winds

Warming or cooling changes the position of the trough, so the region is very sensitive to climate shifts





The eastern lobe of the Caribou Glacier may spill across a bedrock saddle to drain into Donard Lake

Situation

Objective: Obtain annual climate record

Method: Analyze laminae in lake cores in conjunction with 14C dating and magnetic susceptibility



Analysis of Annual Varves

Analysis Numerous studies have shown that

runoff and suspended sediment are a function of summer temperature

Thus, with calibration from historical records, varve thickness is can be used as a climate proxy



--Solid line is varve thickness

--Dotted line is summer temperature

I’m not sure I like this plot.

(and trying to explain the variability with rainfall records doesn’t help much.)



Reconstructed climate record



Reconstructed climate recordLittle Ice Age: 1ºC lower than preceding period




event

Stratigraphy of the Quelccaya ice cap

Objective: reconstruction of a 1.5kyr climatic record

Methods: isotope, conductivity, and microparticle analysis of ice cores



Quelccaya Ice Cap: Largest Glacier in Peru





1980 extent of Quelccaya Ice Cap

55-m-high ice cliff at margin of Quelccaya ice cap. Annual accumulation layers average ¾ m in thickness.



Ice core stratigraphy

Why dust layers? During the dry season, sublimation

concentrates top-level particulates Dominant dry-season wind blows west

or north-west off the dry Peruvian altiplano (plateau).

Faster dry-season winds

Huaynaputina Largest recorded volcanic eruption in

Peru Dates are known precisely to February

and March of 1600 AD

Thus, the thick dust layer from the eruption can be used to place the climate record in time

Huaynaputina & Little Ice Age



How’s the accuracy? For the post-1500 AD record, the

authors give the uncertainty as ±2 years, with an absolute date at 1600.

However, for the lowest part of the core, only visible dust layers could be used for dating, so uncertainty goes up to an estimated ±20 years.

Comparison



Southern and Northern hemisphere temperature records are remarkably similar, implying a global extent for the Little Ice Age.

Conclusions A variety of climate proxies show the

Little Ice Age to be both a significant and a worldwide event.



References Thompson, L.G., et. al. The Little Ice Age recorded in the stratigraphy of the Quelccaya ice

cap. Science, Vol. 234, No. 4774, pgs 361-364. 1986. Moore, J.J., et. al. Little Ice Age recorded in summer temperature reconstruction from

varved sediments of Donard Lake, Baffin Island, Canada. Journal of Paleolimnology 25: 503–517, 2001.

Lewis, D.H., and D.J. Smith. Little Ice Age glacial activity in Strathcona Provincial Park, Vancouver Island, British Columbia, Canada. Can. J. Earth Sci. 41: 285–297(2004)

Lamb, H. H. 1977. Climate & Present, Past and Future. Volume 2. Climatic history and future. Methuen, London

http://www.knowledge4africa.co.za/images-worldhistory/a1ice001.jpg http://en.wikipedia.org/wiki/Image:Solar_Activity_Proxies.png http://en.wikipedia.org/wiki/Image:Carbon-14_with_activity_labels.png http://umarsiddiqi.com/images/industry.jpg http://www.fauna.is/thumbs/BC158landafraediskoft.jpg http://web.utk.edu/~grissino/images/small%20fir.jpg http://pubs.usgs.gov/pp/p1386i/peru/4fig9.gif http://academic.emporia.edu/aberjame/ice/lec19/fig19b.htm http://69.13.97.211/t-shirt-designs/prodimages/smiley%20face.jpg

The Chronology and Stratigraphy of the Little Ice Age Presented by Sara Peek November 27, 2006.

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