The chronology and stratigraphy of the little ice age
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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.

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The chronology and stratigraphy of the little ice age

The Chronology and Stratigraphy of the Little Ice Age

Presented by Sara Peek

November 27, 2006


Overview
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
Background

  • What is the Little Ice Age?


Possible causes
Possible Causes

  • Reduced solar intensity

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


Possible causes1
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
Warming

  • Did the Little Ice Age end because of the Industrial Revolution?


Overview1
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


Dendrochronology lichenometry
Dendrochronology & Lichenometry

Annual tree rings vary in thickness

Lichen Rhizocarpon geographicumincreases in radius over time


Dendrochronology lichenometry1
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


Colonel Foster Glacier

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).



Results

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


Overview2
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


The varved sediments of donard lake
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


Situation

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


Analysis of Annual

Varves

  • Objective: Obtain annual climate record

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


Analysis
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

Little Ice Age: 1ºC lower than preceding period


Overview3
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


Stratigraphy of the quelccaya ice cap
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


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

1980 extent of Quelccaya Ice Cap


Ice core stratigraphy accumulation layers average ¾ m in thickness.


Why dust layers
Why dust layers? accumulation layers average ¾ m in thickness.

  • 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
Huaynaputina accumulation layers average ¾ m in thickness.

  • 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
Huaynaputina & Little Ice Age accumulation layers average ¾ m in thickness.


How s the accuracy
How’s the accuracy? accumulation layers average ¾ m in thickness.

  • 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
Comparison accumulation layers average ¾ m in thickness.

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


Conclusions
Conclusions accumulation layers average ¾ m in thickness.

  • A variety of climate proxies show the Little Ice Age to be both a significant and a worldwide event.


References
References accumulation layers average ¾ m in thickness.

  • 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


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