constraining hydrological cycle characteristics of early eocene hyperthermals   

Constraining Hydrological Cycle

Characteristics of Early Eocene Hyperthermals   

Srinath Krishnan

Reasons for study

Rainfall has direct impact on human society Impact of anthropogenic activity on rainfall

patterns is not well understood Modern studies suggest intensification of

hydrological cycle with warming Wet Wetter Dry Dryer

Lack of data inhibits validation of these models in a complex natural system

Reasons for study

Rainfall has direct impact on human society Impact of anthropogenic activity on rainfall

patterns is not well understood Modern studies suggest intensification of

hydrological cycle with warming Wet Wetter Dry Dryer

Lack of data inhibits validation of these models in a complex natural system

Reasons for study

Rainfall has direct impact on human society Impact of anthropogenic activity on rainfall

patterns is not well understood Modern studies suggest intensification of

hydrological cycle with warming Wet Wetter Dry Dryer

Lack of data inhibits validation of these models in a complex natural system

Reasons for study

Rainfall has direct impact on human society Impact of anthropogenic activity on rainfall

patterns is not well understood Modern studies suggest intensification of

hydrological cycle with warming Wet Wetter Dry Dryer

Lack of data inhibits validation of these models in a complex natural system

Early Eocene HyperthermalsPaleocene-Eocene

Thermal Maximum

• ~3-50C rise in temperature

• Negative carbon isotope excursion of 2.5-6‰

Eocene Thermal Maximum-2

• Smaller rise in temperature compared to the PETM set on a warming trend

• Carbon isotopic excursion about half of the PETM

Adapted from Zachos et al. (2001)

Early Eocene Hyperthermals

Causes Methane Hydrates (Dickens et al., 1995) Burning of terrestrial organic matter (Kurtz et al.,

2003) Estimates of greenhouse gas concentrations

Pre-PETM: ~600 – 2,800 ppm of CO2

PETM: ~750 – 26,000 ppm of CO2 ~1,500 – 55,000 Gt C in the atmosphere ~3,900 – 57,000 Gt C released in the oceans

Modern atmospheric CO2 concentration: ~360 ppm Modern Conventional fossil fuel reserves: ~5,000 Gt C

Early Eocene Hyperthermals

Causes Methane Hydrates (Dickens et al., 1995) Burning of terrestrial organic matter (Kurtz et al.,

2003) Estimates of greenhouse gas concentrations

Pre-PETM: ~600 – 2,800 ppm of CO2

PETM: ~750 – 26,000 ppm of CO2 ~1,500 – 55,000 Gt C in the atmosphere ~3,900 – 57,000 Gt C released in the oceans

Modern atmospheric CO2 concentration: ~360 ppm Modern Conventional fossil fuel reserves: ~5,000 Gt C

GOAL

Use early Eocene hyperthermals as analogues to study changes in the hydrological cycle during extreme warming events

Schematic of a Water Cycle

Adapted from NASA Goddard Flight Center

Expected changes with warming Increased lower tropospheric water vapor

In the extra-tropics, the important components of the hydrological cycle that affect isotopic signals are Horizontal poleward flow of moisture Changes in precipitation and evaporation

Dr. Raymond Schmitt: http://www.whoi.edu/sbl/liteSite.do?litesiteid=18912&articleId=28329

Variations in Precipitation with warming

Held and Soden (2006)

Increased Evaporation

2.80c in 2100

Held and Soden (2006)

Increased Precipitation

Variations in Precipitation with warming

2.80c in 2100

Isotopes and Precipitation

Modern annual precipitation

http://www.waterisotopes.org

Rayleigh Distillation

Clark and Fritz, 1997

Rayleigh Distillation

Clark and Fritz, 1997

Increased depletion with progressive rainout events

Hypotheses

There is a systematic change in moisture transport to the higher latitudes during warming events Are there similar changes in δD between

the two hyperthermals at the higher latitudes?

Can these changes be detected on a global scale?

Can this theoretical model be reproduced with an isotope coupled climate model?

Proxies

n-alkanes: Single chain hydrocarbon with long chain lengths (n-C23-35) indicating terrestrial plant/leaf wax sources

Compound-specific hydrogen isotopic composition represents meteoric water modified by evapotranspiration

Compound-specific carbon isotopic compositions represents environmental and ecological conditions

Proxies

n-alkanes: Single chain hydrocarbon with long chain lengths (n-C23-35) indicating terrestrial plant/leaf wax sources

Compound-specific hydrogen isotopic composition represents meteoric water modified by evapotranspiration

Compound-specific carbon isotopic composition represents environmental and ecological conditions

n-alkanes and precipitation

Adapted from Sachse et al., 2006)

Deute

rium

n-alkanes

Biomarker transport

Adapted from Eglinton and Eglinton, 2008

Continent Oceans

Wind

Terrestrial Plants Rivers

Aerosols (with

waxes)

Methods

Samples

Total Lipid Extract

n-alkane and biomarker fractions

Compound Detection & Identification

Compound-specific Deuterium & Carbon isotope compositions

Crushing and Extraction

Compound Separation

Gas ChromatogramAnalyses

Compound-specific Isotope Ratio Mass Spectrometer

Clean-up Procedures

Analytical Uncertainty: ±5‰

IODP-302 Arctic Coring Expedition

Arctic Paleocene-Eocene Thermal Maximum

Modified from Pagani et al., 2006

~55.6 MaDuration: ~150-200 kyrs

Arctic Eocene Thermal Maximum-2

This work

~54 MaDuration: ~75-100 kyrs

Preliminary Conclusions

Enrichment at the onset for both events with different magnitudes Decreased rainout for moisture reaching the

poles

15-20‰ magnitude depletions during the events Similar variations during both the events

Preliminary Conclusions

Enrichment at the onset for both events with different magnitudes Decreased rainout for moisture reaching the

poles

15-20‰ magnitude depletions during the events Similar variations during both the events

Hypotheses There is a systematic change in

moisture transport to the higher latitudes during hyperthermal events Are there similar changes in δD during the

two hyperthermals at the higher latitudes?

Preliminary Conclusion: Enrichments in δD do correspond with the hyperthermals at the onset of the event with similar magnitude depletions during the eventNumber of samples

Arctic ETM-2: 29 samples

Hypotheses

There is a systematic change in moisture transport to the higher latitudes during hyperthermal events Are there similar changes in δD during the

two hyperthermals at the higher latitudes?

Can these changes be detected on a global scale?

Can this theoretical model be reproduced with an isotope coupled climate model?

Tropical PETM: Tanzania (Handley et al., 2008)

Tropical PETM: Colombia (This work)

Mid-latitudes PETM: Bighorn Basin Smith et al. (2006)

PETM: High LatitudesPagani et al. (2006)

Summary of changes during PETM Tropics

Tanzania – 15‰ enrichment Colombia - ~30‰ depletion

Mid-latitudes Lodo – No change during the event with hints of depletion at

the onset and the end Bighorn Basin – No significant change Forada - ~10‰ enrichment at the onset followed by a10‰

depletion during the event High Latitudes

Arctic – 60‰ enrichment at the onset followed by 20‰ depletion through the event

Summary of changes during PETM Tropics

Tanzania – 15‰ enrichment Columbia - ~30‰ depletion

Mid-latitudes Lodo, California – No change during the event with hints of

depletion at the onset and the end Bighorn Basin – No significant change Forada, Italy - ~10‰ enrichment at the onset followed by

a10‰ depletion during the event High Latitudes

Arctic – 60‰ enrichment at the onset followed by 20‰ depletion through the event

Summary of changes during PETM Tropics

Tanzania – 15‰ enrichment Columbia - ~30‰ depletion

Mid-latitudes Lodo – No change during the event with hints of depletion at

the onset and the end Bighorn Basin – No significant change Forada - ~10‰ enrichment at the onset followed by a10‰

depletion during the event High Latitudes

Arctic – 60‰ enrichment at the onset followed by 20‰ depletion through the event

Hypotheses There is a systematic change in

moisture transport to the higher latitudes during hyperthermal events Can these changes be detected on a

global scale? Preliminary Conclusion: Existing data not

sufficient to draw conclusions about regional & hemispherical changes. Requires further studies on a global scale

Ongoing Work

Ongoing Work: Giraffe Core

C29

Ongoing Work: 1051

C29

Ongoing Work: 1263

C29

Ongoing Work: 690

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Hypotheses

There is a systematic change in moisture transport to the higher latitudes during hyperthermal events Are there similar changes in δD during the

two hyperthermals at the higher latitudes? Can these changes be detected on a global

scale? Can these changes predicted be

reproduced with an isotope coupled climate model?

Future Work: Eocene Modeling Goal

To utilize the global dataset developed to compare the hydrological response in terms of isotopes, temperatures and precipititation signals

Simulations planned Hyperthemal scenarios (PETM vs. ETM2)

Different CO2 concentrations

Background Eocene

Thank You

AcknowledgmentsJoint Oceanographic Institute, ODP/IODP

Mark Pagani, Matt Huber, Appy Sluijs, Carlos JaramilloPeter Douglas, Sitindra Dirganghi, Micheal Hren, Brett Tipple, Katie French, Keith Metzger, Courtney Warren, Matt Ramlow,

Gerry Olack, Dominic ColosiYale G&G Faculty, Staff & Students

Mid-latitudes PETM: Forada Tipple (unpublished)

Mid-latitudes PETM: Lodo Tipple (unpublished)

Paleogeography

C-3 Biosynthetic pathway

C-4 Biosynthetic pathway

Modern mean annual poleward flux

Changes in northward polar flux with doubling of CO2 – IPCC AR-4 scenario

Held & Soden, 2006

Proxies

TEX-86

Derived from marine pico plankton Crenarchaeota

Vary membrane fluidity and composition depending on the temperature

Has recently been applied to analyze paleo-SST

Changes in GWML

Theoretical Model Warming results in increased lower tropospheric

water vapor Scales according to the Clausius-Clayperon

relationship

In the extra-tropics, the important components of the hydrological cycle that affect isotopic signals are horizontal poleward flow of moisture and changes in precipitation and evaporation

Simple models have been developed by scaling with the Clausius-Clayperon relation

€

d lnes

dT=L

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Energy Use Phase

Energy generation Phase

FATTY ACID BIOSYNTHESIS

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ACETYL CO-A

MALONYL CO-A

CH3

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CH2

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