AGU, San Francisco, 2013 Modelled insights into climate dynamics of the Cretaceous and Paleogene greenhouse Dan Lunt, Claire Loptson, Alex Farnsworth,

AGU, San Francisco, 2013

Modelled insights into climate dynamics of the Cretaceous and

Paleogene greenhouseDan Lunt, Claire Loptson, Alex Farnsworth, Paul Markwick

(1) What is the role of palaeogeography across the Cretaceous and Paleogene?

(2) Where can new data be targetted to obtain a ‘pure’ climate signal?

(3) How does palaeogeography influence Climate Sensitivity?


Data from Friedrich et al (2012)

(1) Introduction

What is the role of solar forcing vs. palaeogeographic (including gateways) forcing vs. carbon cycle forcing?

Last 150 Ma:

Major climate trends, + variability + ‘events’


(2) Questions to be addressed

Current paradigm:

Paleogeographical / gateway changes less important than greenhouse gas forcing.

BUT:

Work mostly focussed on a limited number of time periods Lack of consistency across simulations Coarse palaeogeographies Models have improved

SO:

(1) What is the role of palaeogeography (including gateways) across the Cretaceous/Paleogene?(2) Where can new data be targetted to obtain a ‘pure’ climate signal?(3) How does palaeogeography influence Climate Sensitivity? (i.e. “state dependency”).


(3) Experimental DesignPalaeogeographies provided by Getech and Paul Markwick

Created using similar techniques to those outlined in Markwick (2007), based on published lithologic, tectonic and fossil studies, the lithologic databases of the Paleogeographic Atlas Project (University of Chicago), and deep sea (DSDP/ODP) data. Extensively updated from Markwick (2007), e.g. bathymetry, new rotations, more underlying data.

Paleogeographies removed


(3b) Experimental Design


(3b) Experimental Design

The model: HadCM3L (with vegetation)“state-of-the-art”....not.


(3b) Experimental DesignThe model: HadCM3L

How good is it for the palaeo?

Lunt et al, Clim. Past (2012)

Data compiled by Tom Dunkley Jones.


Phase 1 Phase 2 Phase 3 Phase 4D

eep

ocea

n te

mpe

ratu

re

50-years 400-years 57-years 500-1000 years

Pre-industrial CO2

Pre-industrial SSTsPaleogeography'sUniform Veg

Lakes4xCO2

TRIFFIDSolar constantsOzone concentrations

Creation of islandsBaratropic

stremfunction

No Ice + 2 x CO2

Ice + 2 x CO2

Ice + 4 x CO2

(3b) Experimental Design (consistent across all simulations)

Simulation spinup – from Alex Farnsworth


(4) Results

Global means...


(4) Results

SSTs...

e.g.Maximum warmth shifts from W. Pacific to E. Indian ocean in Late Eocene.

Zonal mean relatively constant.

ENSO is a constant feature.

Winter Arctic and Southern Ocean seaice for all time periods.

Animations removed


(4) Results

Regions of deep water formation...

e.g.N. Pacific deep water formation in earliest Cretaceous, gone by Middle Cretaceous.

Mid and late Cretaceous and early Eocene little mixing.

North Atlantic deep water formation kicks off ~40 Ma.

Animations removed


(4) Results

Vegetation...

e.g.Expansive N and S American deserts in early Cretaceous.

‘Green’ Sahara develops in late Eocene.

Animations removed


(4) Results

Single sites...


(4) Results

Implications for site targetting...Where are the locations with least paleography-related change; i.e. Where to go for a ‘pure’ CO2 signal:

Marine Terrestrial


(4) Results

Climate Sensitivity


(4) Results

Climate Sensitivity

3.3oC 2.8oC 3.0oC 2.8oC

3.0oC 3.2oC 2.5oC


Summary

Cretaceous and Paleogene simulations broadly support the paradigm that carbon cycle dominates over palaeogeography forcing.

BUT, at single sites, the temperature changes due to palaeogeography alone can be very large.

AND, other aspects of the system, such as ocean circulation and vegetation, can also show very large palaeogeographically-driven changes.

Simulations can point to where a ‘pure’ CO2 signal could be obtained.

Climate Sensitivity is a function of palaeography, varying by 30% through the late and mid Cretaceous.


(5) Future work

CESM simulations

Early Cretaceous grid Late Cretaceous grid

Modern DMS emissionsModern DMS emissions“paleo-tised”

Early Cretaceous DMS emissions

Late Cretaceous DMS emissions


(5) Future work

NERC project: Cretaceous-Paleocene-Eocene: Exploring Climate and Climate Sensitivity

Complete CO2 sensitivities

Ice sheets [e.g. role of CO2, gateways and ice sheets at E-O boundary]

Model internal parameter sensitivity studies.

Data compilations (Stuart Robinson, Oxford). Back-out model-derived CO2 record

Equivalent future simulations

Sagoo et al, Phil Trans, in press.

Kiehl et al, Phil Trans, in press.

Lunt et al, Phil Trans, in press.

.


(5) Future work

Complete Neogene simulations. Role of orbital forcing

PMIP working group on ‘pre-Pliocene climates’

Joint venture between data and modelling communities

Model output available.Email: [email protected]

AGU, San Francisco, 2013Dan Lunt

“Warm Climates of the Past – A lesson for the future?”

Special Issue of Phil Trans A

All papers now ‘in press’

Including contributions from:Badger, DeConto, Dowsett, Foster, Hansen, Haywood, John, Kiehl, Lunt, Otto-Bliesner, Pagani, Pancost, Pearson, Sagoo, Valdes, Zachos, Zeebe, Zhang.

Early Eocene, ~55 - 50 Ma

Mid-Pliocene, ~3.3 - 3 Ma

Last Interglacial, 135-130 ka

...future, 2100

Using the palaeo to inform the future

http://www.paleo.bris.ac.uk/~ggdjl/warm_climates.html

Documents

AGU, San Francisco, 2013 Modelled insights into climate dynamics of the Cretaceous and Paleogene greenhouse Dan Lunt, Claire Loptson, Alex Farnsworth,