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A 13,000-year regional record of Holocene storms in the northeastern United States. Anders Noren University of Vermont Funding: NSF Career Grant EAR-9702643. • Rain-induced erosion • Deposition in lakes. Ritterbush Analyses. PS. MS. CH. GD. LOI. %C. %N. C/N. d 13 C. 1 cm. - PowerPoint PPT Presentation
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A 13,000-year regional record of Holocene storms in the northeastern United States
Anders NorenUniversity of Vermont
Funding: NSF Career Grant EAR-9702643
• • Rain-induced erosionRain-induced erosion• • Deposition in lakesDeposition in lakes
L MC /N δ13 PC G NCH GD LOI %C %N C/N δ13C PS MSRitterbush Analyses
1 cm
Other Mechanisms
• Earthquakes• Snowmelt• Lake-level fluctuations• Removal of vegetation
- Drought, disease- Fires- Human activity
Why Storms?• Written records correlate with paleostorm reconstructions
- Layer occurrence- Layer thickness
• Field observations
2000
2600
5900680082009400
The Ritterbush Record 50 cm
Cal
enda
r Yea
rs B
P
QuestionsDoes the Ritterbush record reflect regional processes?• Storm size: Hurricanes or localized
storms? (Were layers depositedsynchronously in multiple lakes?)
• Regional storm trends: Periods ofincreased storminess? Cycles?
Climatic causes/controls?
• • SteepSteep• • DeepDeep• • Evidence ofEvidence ofsediment transportsediment transport
Lake Characteristics
Lake TownArea (km2)
Depth (m)
Basin Relief (m)
Amherst Plymouth, VT 0.33 27 675Beebe Hubbardton, VT 0.45 13 215Chapel Saint Huberts, NY 0.07 24 925Duck Sutton, VT 0.03 14 290Dunmore Salisbury, VT 3.99 32 812Echo Plymouth, VT 0.42 28 678Elligo Greensboro, VT 0.70 30 259Emerald Dorset, VT 0.13 13 713Morey Fairlee, VT 2.22 13 414Ritterbush Eden, VT 0.05 14 293Richmond Richmond, VT 0.10 3 273Thirteenth North River, NY 1.33 15 536Vail Sutton, VT 0.06 14 354
Lake Locations
Coring DeviceDriverDriver
HeadHead
BarrelBarrel
Piston
6m
Analytical Tools
• Magnetic Susceptibility (MS)
• X-Radiography (XR)
• Visual Logging: color, texture (VL)
• Loss-on-Ignition (LOI)
• AMS-Radiocarbon Analysis (14C)
VL50
100
150
200
250
300
XR
Dep
th (c
m)
MSLOI0 25 0 50
Time Series Filter
• Remove negative peaks > 1from median
• SSA reconstruction of remaining series
• Peaks > 1 from reconstruction = SIGNIFICANT
VL50
100
150
200
250
300
XRD
epth
(cm
)LOI MS MSLOI
VL50
100
150
200
250
300
XRD
epth
(cm
)LOI MS MSLOI COMP
AMS 14C Analysis
• 80 dates• John Southon, Lawrence Livermore National Laboratory
1070010800109001100011100112009400
9500
9600
9700
9800AMS Date1 sigma14C Curve
Calendar Years BP
14C
Yea
rs B
P
Dep
th (c
m)
0
200
400
600
0 5000 10000 15000
Age Model (yr)
Radiocarbon AgesCalibrated Ages
Removeeventlayers
Compresscore
VLVLVL50
100
150
200
250
300
EventsVL50
100
150
200
250
300
1400
3000
5200
Dates
14002100, 2150
Model Ages
3000, 31203400, 3790
4800, 49505200
Discussion
• Storm size• Storm magnitude• Storm frequency
—> Climate:New England and North Atlantic
Storm Size
0 2 4 6 8 10 12 14Calendar kyr BP
Terrigenous Layer
End of Record
Storm Size
Terrigenous Layer
End of Record
• Small storms locally as damaging as large
0 2 4 6 8 10 12 14Calendar kyr BP
0 2 4 6 8 10 12 14Calendar kyr BP
Terrigenous Layer
End of Record
Storm Magnitude
11-point avg.
0
7
0 2 4 6 8 10 12Calendar kyr BP
Avg
. Lay
er
Thic
knes
s (c
m)
Storm Magnitude
• Magnitude highest in early and late Holocene
11-point avg.
0
7
0 2 4 6 8 10 12Calendar kyr BP
Avg
. Lay
er
Thic
knes
s (c
m)
Spectral Analysis
0 100 200 300 0 0.05 0.1
0 100 200 300 0 0.05 0.1Time Frequency
0 100 200 300 0 0.05 0.1
0 100 200 300 0 0.05 0.1Time Frequency
Another Spectrogram…
Storm Magnitude
11-point avg.
0
7
0 2 4 6 8 10 12Calendar kyr BP
Avg
. Lay
er
Thic
knes
s (c
m)
Storm Magnitude
0
5
0 1 2 3 4 5
Raw SpectrumHarmonic99% CI95% CI90% CI
Frequency (cycles/kyr)
Storm Magnitude
0
5
0 1 2 3 4 5
Raw SpectrumHarmonic99% CI95% CI90% CI
• 500-year cycle: Ocean circulation? Solar?Frequency (cycles/kyr)
Terrigenous Layer
End of Record
0 2 4 6 8 10 12 14Calendar kyr BP
Storm Frequency
0 2 4 6 8 10 12Calendar kyr BP
Storm Frequency
0.0
0.3
0 1 2 3 4 5
Raw SpectrumHarmonic99% CI95% CI90% CI
Frequency (cycles/kyr)• 3000-year cycle
Storm Frequency
• 4 maxima; currently increasing—observed?
0 2 4 6 8 10 12Calendar kyr BP
New EnglandClimate
0 2000 4000 6000 8000 10000 12000
Cool, moist
Warm, dry
Cool, moist
Mag.
Freq.
Fans
Avg.
0 2 4 6 8 10 12Calendar ky BP
NorthAtlanticClimate
GISP2 nssK
GISP2 ssNa
Coolings
StormFreq.
StormsFloods
0 2 4 6 8 10 12Calendar kyr BP
Arctic Oscillation
High phase• zonal flow• Europe warm
Low phase• meridional flow• Europe cold
Factors Pointing to AO Involvement
1. Storminess correlates with GISP2 • GISP2 maxima imply meridional flow • Meridional flow :: low-phase AO2. Storm maxima occur when
Europe is cold • Cold in Europe :: low-phase AO3. Modern relationship established
NorthAtlanticClimate
GISP2 nssK
GISP2 ssNa
Coolings
StormFreq.
StormsFloods
0 2 4 6 8 10 12Calendar kyr BP
Implications of AO involvement
Dominant atmospheric modes • AO, ENSO
Long-timescale climate forcing • Ocean thermohaline circulation • Solar variability
Conclusions
1. Storm Size • Small storms locally as damaging
as hurricanes/nor’easters
2. Storm Magnitude • 500-year cycle: cause? • Highest when climate is cool, moist
Conclusions
3. Storm Frequency • 3000-year cycle • 4 Holocene maxima • Currently increasing—observed? • Maxima correlate with fans, floods,
storms, cool periods • Relationships consistent with AO • Probable solar forcing
Acknowledgements
Paul BiermanAndy BosleySarah BrownGordon ChadburnAngie ConlanBen CopansJen CunninghamDavid FlemingGretchen FowlesClaude GaboriaultJosh Galster
Gagan MirchandaniKyle NicholsAdam ParrisSimon RupardJohn SouthonEric SteigStephen TurgeonCarrie WilliamsStephen WrightGeohydrology
Class 1999
I thank NSF for funding,and the following people for their work and guidance.
Doug GomezSara GranRachael HowseForrest JanukajtisKaren JenningsNeil KammanDrew LamneckAndrea LiniAndi LordLaura MallardChristine Massey
Grain Size Analysis
0 500Depth (cm)
(Bos
ley)
(C
onla
n)COMP
COMP
GS
GS
Low-Phase AO Temp. Anomalies
Arctic Oscillation
High phase• zonal flow• Europe warm
Low phase• meridional flow• Europe cold
105001075011000112500
0.001
0.002
0.003
1 sigmaInterceptsProbability
Calendar Years BP
Prob
abili
ty
Calendar Years BPPr
obab
ility
14C
Yea
rs B
PCalibration
10500112500
0.003
1 sigmaInterceptsProbability
10700112009400
9800AMS Date1 sigma14C Curve
Another Spectrogram…