Earth’s Biosphere Interaction of physical processes in Earth’s Interaction of physical processes in Earth’s

climate system with biosphereclimate system with biosphere Results from the movement of carbonResults from the movement of carbon

Carbon Cycle Carbon moves freely between reservoirsCarbon moves freely between reservoirs

Flux inversely related to reservoir sizeFlux inversely related to reservoir size

Photosynthesis

Sunlight, nutrients, HSunlight, nutrients, H22OO Transpiration in Transpiration in

vascular plantsvascular plants Efficient transfer of Efficient transfer of

HH22O(v) to atmosphereO(v) to atmosphere

Oxidation of COxidation of Corgorg

BurningBurning DecompositionDecomposition

2612622 666 OOHCOHCOoxidation

esisphotosynth

Terrestrial Photosynthesis COCO22 and sunlight and sunlight

plentifulplentiful HH220 and correct 0 and correct

temperature for temperature for specific plants not specific plants not always sufficientalways sufficient

Biomass and biome Biomass and biome distribution distribution controlled by rainfall controlled by rainfall and temperatureand temperature

Local Influence on Precipitation

Orographic precipitation influences distribution Orographic precipitation influences distribution of biomass and biomesof biomass and biomes

Influences the distribution of precipitationInfluences the distribution of precipitation

Marine Photosynthesis HH22O, COO, CO22 and sunlight and sunlight

plentifulplentiful Nutrients low (N, P)Nutrients low (N, P) Nutrients extracted Nutrients extracted

from surface water by from surface water by phytoplanktonphytoplankton

Nutrients returned by Nutrients returned by recyclingrecycling Upper ocean (small)Upper ocean (small) Upwelling (high)Upwelling (high) External inputs External inputs

(rivers, winds)(rivers, winds)

Ocean Productivity Related to supply of Related to supply of

nutrientsnutrients Nutrient supply high Nutrient supply high

in upwelling regionsin upwelling regions Equatorial upwellingEquatorial upwelling Coastal upwellingCoastal upwelling

Southern OceanSouthern Ocean Wind-driven mixingWind-driven mixing Short growing Short growing

seasonseason Light limitationLight limitation

Productivity – Climate Link ““Biological Pump” Biological Pump”

– photosynthesis – photosynthesis takes up COtakes up CO22 and and nutrients, plants nutrients, plants eaten by eaten by zooplankton, zooplankton, dead zooplankton dead zooplankton or excreted or excreted matter sinks matter sinks carrying carbon carrying carbon to sedimentsto sediments

Export – Removal of Carbon For every 1000 carbon For every 1000 carbon

atoms taken up by atoms taken up by phytoplanktonphytoplankton

50-100 sink below 100 50-100 sink below 100 mm

10 are exported to 10 are exported to depths below 1 kmdepths below 1 km Stored for millenniaStored for millennia

1 carbon atom is buried 1 carbon atom is buried in deep sea sedimentsin deep sea sediments Sequestered for eonsSequestered for eons

HNLC Growth in regions limited by micronutrients (Fe)Growth in regions limited by micronutrients (Fe)

High nutrient low chlorophyll (N. Pacific, SO)High nutrient low chlorophyll (N. Pacific, SO) Higher production linked with removal of COHigher production linked with removal of CO22

Effect of Biosphere on Climate Changes in greenhouse gases (COChanges in greenhouse gases (CO22, CH, CH44)) Slow transfer of COSlow transfer of CO22 from rock reservoir from rock reservoir

Does not directly involve biosphereDoes not directly involve biosphere 10-100’s millions of years10-100’s millions of years

COCO22 exchange between shallow and exchange between shallow and deep oceandeep ocean 10,000-100,000 year10,000-100,000 year

Rapid exchange between ocean, Rapid exchange between ocean, vegetation and atmospherevegetation and atmosphere Hundreds to few thousand yearsHundreds to few thousand years

Increases in Greenhouse Gases COCO22 increase anthropogenic increase anthropogenic

and seasonaland seasonal Anthropogenic – burning Anthropogenic – burning

fossil fuels and fossil fuels and deforestationdeforestation

Seasonal – uptake of COSeasonal – uptake of CO22 in N. hemisphere in N. hemisphere terrestrial vegetationterrestrial vegetation

Methane increase Methane increase anthropogenicanthropogenic Rice patties, cows, Rice patties, cows,

swamps, termites, swamps, termites, biomass burning, fossil biomass burning, fossil fuels, domestic sewagefuels, domestic sewage

Climate Archives Four major archives of climate recordsFour major archives of climate records

SedimentsSediments IceIce CoralsCorals TreesTrees

Each archive has different time span, Each archive has different time span, resolution and ease of datingresolution and ease of dating

Understanding Climate Change

Understanding present climate and predicting Understanding present climate and predicting future climate change requiresfuture climate change requires TheoryTheory Empirical observations Empirical observations

Study of climate change involves construction Study of climate change involves construction (or reconstruction) of time series of climate data(or reconstruction) of time series of climate data How these climate data vary across time How these climate data vary across time

provides a measure (quantitative or provides a measure (quantitative or qualitative) of climate changequalitative) of climate change

Types of climate data include temperature, Types of climate data include temperature, precipitation (rainfall), wind, humidity, precipitation (rainfall), wind, humidity, evapotranspiration, pressure and solar evapotranspiration, pressure and solar irradianceirradiance

Contemporary & Past Climate Contemporary climate studies use empirically Contemporary climate studies use empirically

observed instrumental dataobserved instrumental data Temperature records available from central Temperature records available from central

England beginning in the 17England beginning in the 17thth century century Period traditionally associated with Period traditionally associated with

instrumental records extends back to instrumental records extends back to middle of the 19middle of the 19thth century century

Climate change from periods prior to the Climate change from periods prior to the recording of instrumental datarecording of instrumental data Must be reconstructed from indirect or Must be reconstructed from indirect or

proxy sources of informationproxy sources of information

Climate Construction from Instrumental

Data Contemporary climate change studied Contemporary climate change studied

by constructing records (daily, monthly by constructing records (daily, monthly and annual) which have been obtained and annual) which have been obtained with standard equipmentwith standard equipment TemperatureTemperature RainfallRainfall HumidityHumidity WindWind

Paleoclimate Reconstructions Climate varies over different time scales Climate varies over different time scales

and each periodicity is a manifestation of and each periodicity is a manifestation of separate forcing mechanismsseparate forcing mechanisms

Different components of the climate Different components of the climate system change and respond to forcing system change and respond to forcing factors at different ratesfactors at different rates

To understand the role each component To understand the role each component plays in the evolution of climate we must plays in the evolution of climate we must have a record longer than the time it have a record longer than the time it takes for the component to undergo takes for the component to undergo significant changesignificant change

Paleoclimatology Study of climate change prior to the period of Study of climate change prior to the period of

instrumental measurementsinstrumental measurements Instrumental records span only a fraction Instrumental records span only a fraction

(<10(<10-7-7) of Earth's climatic history) of Earth's climatic history Provide a inadequate perspective on Provide a inadequate perspective on

climatic variation and the evolution of the climatic variation and the evolution of the climate today and in the futureclimate today and in the future

A longer perspective on climate variability A longer perspective on climate variability can be obtained by the study of natural can be obtained by the study of natural climate-dependent phenomenaclimate-dependent phenomena

Such phenomena provide a proxy record of Such phenomena provide a proxy record of the climatethe climate

Paleoclimate Proxy Records Many natural systems are dependent on climateMany natural systems are dependent on climate

It may be possible to derive paleoclimatic It may be possible to derive paleoclimatic information from theminformation from them

By definition, such proxy records of climate all By definition, such proxy records of climate all contain a climatic signalcontain a climatic signal The signal may be weak and embedded in a The signal may be weak and embedded in a

great deal of (climatic) background noisegreat deal of (climatic) background noise Proxy material acts as a filter, transforming Proxy material acts as a filter, transforming

climate conditions in the past into a relatively climate conditions in the past into a relatively permanent recordpermanent record

Deciphering that record can often be complexDeciphering that record can often be complex

Proxy Data Proxy material can differ according toProxy material can differ according to

Its spatial coverageIts spatial coverage The period to which it pertainsThe period to which it pertains Its ability to resolve events accurately in timeIts ability to resolve events accurately in time

For exampleFor example Ocean floor sediments, reveal information about Ocean floor sediments, reveal information about

long periods of climatic change and evolution (10long periods of climatic change and evolution (1077 years), with low-frequency resolution (10years), with low-frequency resolution (1033 years) years)

Tree rings useful only during the last 10,000 Tree rings useful only during the last 10,000 years, but offer high frequency (annual) resolutionyears, but offer high frequency (annual) resolution

The choice of proxy record (as with the choice of The choice of proxy record (as with the choice of instrumental record) depends on physical instrumental record) depends on physical mechanism under reviewmechanism under review

Factors to Consider When using proxy records to reconstruct When using proxy records to reconstruct

paleoclimates one must considerpaleoclimates one must consider The continuity of the recordThe continuity of the record The accuracy to which it can be dated The accuracy to which it can be dated

Ocean sediments may be continuous for over 1 Ocean sediments may be continuous for over 1 million years but are hard to datemillion years but are hard to date

Ice cores may be easier to date but can miss Ice cores may be easier to date but can miss layers due to melting and wind erosionlayers due to melting and wind erosion

Glacial deposits are highly episodic, providing Glacial deposits are highly episodic, providing evidence only of discrete events in the pastevidence only of discrete events in the past

Different proxy systems have different levels of inertia Different proxy systems have different levels of inertia with respect to climatewith respect to climate Some systems vary in phase with climate forcingSome systems vary in phase with climate forcing Some systems lag behind by as much as several Some systems lag behind by as much as several

centuriescenturies

Steps in Reconstructing Climate

Paleoclimate reconstruction proceeds through Paleoclimate reconstruction proceeds through a number of stagesa number of stages The 1The 1stst stage is proxy data collection, stage is proxy data collection,

followed by initial analysis and measurementfollowed by initial analysis and measurementThis results in primary dataThis results in primary data

The 2The 2ndnd stage involves calibration of the data stage involves calibration of the data with modern climate recordswith modern climate records

The secondary data provide a record of The secondary data provide a record of past climatic variationpast climatic variation

The 3The 3rdrd stage is the statistical analysis of this stage is the statistical analysis of this secondary datasecondary data

The paleoclimatic record is statistically The paleoclimatic record is statistically described and interpreteddescribed and interpreted

Proxy Calibration The uniformitarian principle is typically The uniformitarian principle is typically

assumedassumed Contemporary climatic variations form Contemporary climatic variations form

a modern analog for paleoclimatic a modern analog for paleoclimatic changeschangesHowever the possibility always exists However the possibility always exists that paleo-environmental conditions that paleo-environmental conditions may not have modern analogsmay not have modern analogs

The calibration may be only qualitative, The calibration may be only qualitative, involving subjective assessment, or it involving subjective assessment, or it may be highly quantitativemay be highly quantitative

Proxy Calibration: An Example Emiliania huxleyiEmiliania huxleyi is one is one

of 5000 or so species of of 5000 or so species of phytoplanktonphytoplankton

Most abundant Most abundant coccolithophore on a coccolithophore on a global basis, and is global basis, and is extremely widespread extremely widespread Occurs in all except Occurs in all except

the polar oceansthe polar oceans Produces unique Produces unique

compoundscompounds CC3737-C-C3939 di-, tri- and di-, tri- and

tetraunsaturated tetraunsaturated methyl and ethyl methyl and ethyl ketonesketones

Emiliania huxleyi Blooms E. huxleyiE. huxleyi can occur can occur

in massive bloomsin massive blooms 100,000 km100,000 km22

During blooms During blooms E. E. huxleyihuxleyi cell cell numbers usually numbers usually outnumber those outnumber those of all other of all other species combinedspecies combined

Frequently they Frequently they account for 80 account for 80 or 90% of the or 90% of the total number of total number of phytoplanktonphytoplankton SeaWiFS satellite image of bloom off

Newfoundland in the western Atlantic on 21 July 1999

Emiliania huxleyi Makes Alkenones

UK’37 Varies with Temperature

Alkenone unsaturation Alkenone unsaturation global calibrationglobal calibration UUK’K’

3737 determined in determined in core top sediment core top sediment samplessamples

SST from from SST from from Levitus ocean atlasLevitus ocean atlas

Figure from Muller Figure from Muller et al.et al. (1998) (1998)

Global UK’37 SST Correlation