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…