Paleoclimatic Research:

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Paleoclimatic Research Creating a Holocene
Climate Record for Iceland Using Proglacial
Lacustrine Sediments
Anna Wagner Undergraduate, University of
Colorado Department of Geologic Sciences and
Environmental Sciences DOSECC Workshop 2005
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Why Iceland? North Atlantic Sensitivity Glacial
records Soft bed rock Diagnostic tephras
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Research Questions
Did the large icecaps disappear during maximum
Holocene warmth?
What is the magnitude and timing (cyclicity?)
of Holocene environmental change?
How unusual is 20th century warmth? Annual
resolution is needed to answer the last two
questions
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(Black, J., et al. 2004)

• The ice cap itself has a gradual relief which
  allows small changes in the ELA to result in
  large changes of the accumulation area
• High sedimentation rates

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Hvítárvatn sediment

LIA
Neoglaciation
HTM
Deglacial sediment
Glacial deposit
Bedrock
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Conclusions thus far

• Yes, the ice cap was gone during the early
  Holocene and the temperatures were warmer, HTM
• Ice sheet modeling currently underway in means
  to determine magnitude and timing of Holocene
  environmental change
• Currently, creating high resolution
  (sub/decadal) data to confirm and detail the
  extent to which these changes have taken place
• Proxies being used BiSO2, TOC, tephra layers,
  diatoms, pollen, magnetic susceptibility, 14C
  ages

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HvítárvatnSeasonally Laminated ?

X-ray Visual
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Importance of Varved Sediments

• Provide high resolution climate record
• from which we can infer
• How unusual is the rate and magnitude of climate
  change or warming in the 20th century is
• If there is a quasi-periodic cyclicity in
  Holocene environmental change on Iceland

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Hvítárvatn HVT04-13
Core taken at a depth of 51 m depth

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• (Note x-ray colors inverted from color photos)
• Sedimentary structures easily visible with x-rays
• (ex. small scale cross lamination)
• No graded bedding, no reworking of the core

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Hypothesis

• Depositional Environment Laminae Color
• Ice Cover. Yellow
• Catchment Runoff.. Olives
• Sub-glacial fluvial processes
• and calving ... Black

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Methods

• Sampling of Core
• Grain Size
• to examine physical grain size differences
  between laminae
• Instrumentation used was the Malvern
• Diatom Assemblages
• to examine seasonal successions within the
  varve
• Iowa Lake Side Lab summer course
• Total Organic Carbon
• to examine periods of higher productivity of
  the lake
• CM5012 CO2 Coulometer

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Sampling HVT04-13

• -22 annual varves
• -83 laminae
• Bottom of Core is thought to be deposited in 1975

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Average Grain Size Distribution
Clay Silt Sand
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Average Grain Size Distribution by Laminae
Percentage
Olive
Yellow
Black
Laminae Color
Clay Silt Sand
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Conclusions from Grain Size

• Laminae of yellow, olive and black are physically
  differentiable by grain size
• Clay content increase with lighter color
• Sand and silt content increases with darker color
• This represents that source of sediment or energy
  of environment must be changing between laminae

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DIATOMS
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Conclusions from Diatoms

• Much higher abundance of diatoms present in
  darker sediments
• -climatically optimal
• Fragilaria is ice tolerant and is not found in
  yellow laminae but large influx in black laminae
• -habitat lost
• River species abundance spikes in olive sediments
• -lotic species are washed in with snowmelt via
  fluvial systems

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Total Organic Carbon Percents
Black---
Dark Olive--
Olive---
Light Olive--
Yellow---
Total organic carbon
With an error bar of 0.2 these data provide
little help
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• Weather Vs. Climate
• Stratigraphy is not cut and dry Yellow, Olive,
  Black
• Noticeable interruptions
• Due to high sediment deposition of environment,
  noise likely represents persistent weather events

• FURTHER WORK
• working with daily weather data and
  stratigraphy for correlations

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Conclusions
Nordurjokull

• The sediments of Hvítárvatn are seasonally
  laminated

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Conclusions
A Large Thank You To Dr. Gifford
Miller Dr. Áslaug Geirsdóttir Ms. Jessica
Black Dr. James White Dr. Sarah
Spaulding Ms. Wendy Roth Drilling,
Observation, and Sampling of the Earths
Continental Crust, Inc., (DOSECC) Undergraduate
Research Opportunities (UROP) University of
Colorado

• The sediments of Hvítárvatn are Seasonally
  laminated with a high likelihood weather events
  are also recorded!