Dendroclimatology Dendroclimatology (relationship between Dendroclimatology (relationship between

annual tree growth and climate) offers high annual tree growth and climate) offers high resolution paleoclimate reconstruction for resolution paleoclimate reconstruction for most of the Holocenemost of the Holocene

Huon pine - Huon pine - Lagarostrobos frankliniiLagarostrobos franklinii A conifer endemic to Tasmania is A conifer endemic to Tasmania is

recognized as the longest living tree (or recognized as the longest living tree (or organism) knownorganism) knownA medium sized specimen growing on A medium sized specimen growing on

the west coast of Tassie is estimated to the west coast of Tassie is estimated to be about 10,000 years oldbe about 10,000 years old

Lagarostrobos franklinii

Sequoiadendron giganteum

Tree Rings Cross section of temperate forest tree trunks Cross section of temperate forest tree trunks

reveal alternation of light and dark bandsreveal alternation of light and dark bands Seasonal growth increments consisting of Seasonal growth increments consisting of

earlywood (light growth band from early earlywood (light growth band from early part of the growing season) and denser part of the growing season) and denser latewood (a dark band produced towards latewood (a dark band produced towards the end of the growing season)the end of the growing season)

Mean width of tree rings are a function of Mean width of tree rings are a function of tree species, tree age, soil nutrient tree species, tree age, soil nutrient availability and a whole host of climatic availability and a whole host of climatic factorsfactors

Dendroclimatologist must extract climatic Dendroclimatologist must extract climatic signals available in the tree-ring data from signals available in the tree-ring data from remaining background "noise"remaining background "noise"

Tree Ring Banding

Splicing Tree Ring Records

Sampling Tree Rings

Climate Information from Trees Tree growth can be limited directly or indirectly by Tree growth can be limited directly or indirectly by

some climate variablesome climate variable If the limitation can be quantified and dated, If the limitation can be quantified and dated,

dendroclimatology can be used to reconstruct dendroclimatology can be used to reconstruct some information about past environments some information about past environments

Trees growing near the extremes of their ecological Trees growing near the extremes of their ecological niche are subject to climatic stresses – typically niche are subject to climatic stresses – typically moisture and temperature stressmoisture and temperature stress Trees in semi-arid regions are frequently limited Trees in semi-arid regions are frequently limited

by the availability of waterby the availability of water Dendroclimatic indicators reflect waterDendroclimatic indicators reflect water

Trees growing near the latitudinal or altitudinal Trees growing near the latitudinal or altitudinal tree line are frequently temperature limitedtree line are frequently temperature limited

Dendroclimatic indicators reflect temperatureDendroclimatic indicators reflect temperature

Extreme Ecological Niche

Sediments Marine sediments accumulating in ocean basins Marine sediments accumulating in ocean basins

can indicate climate conditions in the surface can indicate climate conditions in the surface ocean or on the adjacent continentsocean or on the adjacent continents Sediments are composed of both biogenic and Sediments are composed of both biogenic and

terrigenous materialsterrigenous materials Biogenic components include planktonic and Biogenic components include planktonic and

benthic organismsbenthic organisms The nature and abundance of terrigenous The nature and abundance of terrigenous

materials provides information about materials provides information about continental weathering and the intensities continental weathering and the intensities and directions of windsand directions of winds

Ocean sediment records have been used to Ocean sediment records have been used to reconstruct climate change ranging from reconstruct climate change ranging from thousands of years to tens of millions of years in thousands of years to tens of millions of years in the pastthe past

Biogenic Sediments Calcareous or siliceous oozesCalcareous or siliceous oozes Three types of analysis of calcareous and Three types of analysis of calcareous and

siliceous tests are typically used for climate siliceous tests are typically used for climate reconstructionreconstruction The oxygen isotopic composition of The oxygen isotopic composition of

calcium carbonatecalcium carbonate The relative abundance of warm- and cold-The relative abundance of warm- and cold-

water specieswater species The morphological variations in particular The morphological variations in particular

species resulting from environmental species resulting from environmental factorsfactors

Isotopic Composition of Shells First general rule of isotope geochemistryFirst general rule of isotope geochemistry

Heavy isotopes concentrate in the Heavy isotopes concentrate in the compound where bond energy is strongestcompound where bond energy is strongest

When a mineral forms in water, heavy When a mineral forms in water, heavy isotope concentrates in the mineralisotope concentrates in the mineral The isotopic composition is a function ofThe isotopic composition is a function of

The isotopic composition of the waterThe isotopic composition of the waterThe temperature of formationThe temperature of formation

•Fractionation decreases as Fractionation decreases as temperature increasestemperature increases

The 18O of Shells Temperature dependentTemperature dependent

T = 16.9 - 4.2 (T = 16.9 - 4.2 (cc - - ww) + 0.13 () + 0.13 (cc - - ww))22 Isotopic variations in carbonates smallIsotopic variations in carbonates small For modern analyses, For modern analyses, ww can be can be

measured directly in ocean water measured directly in ocean water samples; in fossil samples, however, samples; in fossil samples, however, the isotopic composition of sea water is the isotopic composition of sea water is unknown and cannot be assumed to unknown and cannot be assumed to have been the same as it is todayhave been the same as it is today

Glacial/Interglacial change in 18O

Interglacial scenario:Interglacial scenario: High sea- High sea-level stand coupled with little ice level stand coupled with little ice at the poles and relatively little at the poles and relatively little storage of storage of 1616O in ice caps leads to O in ice caps leads to relatively sea-water rich in relatively sea-water rich in 1616O. O. Calcareous organisms living in Calcareous organisms living in the oceans will incorporate more the oceans will incorporate more 1616O in their carbonate shells. O in their carbonate shells. Clouds contain high proportion of Clouds contain high proportion of the light isotope because of it's the light isotope because of it's higher vapor pressure.higher vapor pressure.

Glacial scenario:Glacial scenario: Low seal level Low seal level stands with much polar ice will stands with much polar ice will store more store more 1616O and thus sea O and thus sea water will contain a higher water will contain a higher proportion of proportion of 1818O; this proportion O; this proportion will be mirrored by calcareous will be mirrored by calcareous organisms that live and organisms that live and fractionate this water when they fractionate this water when they form their shell. Clouds contain form their shell. Clouds contain high proportion of the light high proportion of the light isotope because of it's higher isotope because of it's higher vapor pressure.vapor pressure.

Trends in 18O During glacial timesDuring glacial times

Sea water enriched in Sea water enriched in 1818OO Surface water colderSurface water colder

1818O of planktonic calcareous O of planktonic calcareous organisms more positiveorganisms more positive

During interglacial timesDuring interglacial times Sea water enriched in Sea water enriched in 1616OO Surface water warmerSurface water warmer

1818O of planktonic calcareous O of planktonic calcareous organisms more negativeorganisms more negative

Constraining 18O of Seawater Isotopic records of deep water organisms can Isotopic records of deep water organisms can

helphelp Bottom water temperatures (» -1°C to 2°C) Bottom water temperatures (» -1°C to 2°C)

have changed little since glacial timeshave changed little since glacial times Therefore increases in the Therefore increases in the 1818O of deep O of deep

water organisms mostly reflect changes in water organisms mostly reflect changes in the isotopic composition of the glacial the isotopic composition of the glacial oceanocean

Concluded that 70% of the changes in the Concluded that 70% of the changes in the isotopic composition of surface dwelling isotopic composition of surface dwelling organisms was due to changes in the isotopic organisms was due to changes in the isotopic composition of the oceans, and only 30% due composition of the oceans, and only 30% due to temperature variationsto temperature variations

Other Complications – Vital Effects

Unfortunately calcareous marine organisms Unfortunately calcareous marine organisms never took a course in chemical never took a course in chemical thermodynamicsthermodynamics They do not precipitate their shell in oxygen They do not precipitate their shell in oxygen

isotope equilibrium with seawater isotope equilibrium with seawater Calcareous organisms commonly display Calcareous organisms commonly display

“vital” isotope effects “vital” isotope effects For example, incorporation of metabolically For example, incorporation of metabolically

produced carbon dioxideproduced carbon dioxide Vital isotope effects are not a problem ifVital isotope effects are not a problem if

They are knownThey are known They are constantThey are constant

Other Biotic Climate Data Climate reconstruction can be achieved by Climate reconstruction can be achieved by

studyingstudying Relative abundances of speciesRelative abundances of species Species assemblagesSpecies assemblages Morphological variationsMorphological variations

Test coiling directions, either right-Test coiling directions, either right-coiling (dextral) or left-coiling (sinistral), coiling (dextral) or left-coiling (sinistral), reveal proxy information about paleo-reveal proxy information about paleo-temperatures of the oceans temperatures of the oceans

Other variations include differences in Other variations include differences in test size, shape and surface structuretest size, shape and surface structure

Corals Coral skeleton are colonies Coral skeleton are colonies

composed of polyps composed of polyps Symbiotic algae (zooxanthellae)Symbiotic algae (zooxanthellae)

Zooxanthellae supply both Zooxanthellae supply both with food and oxygenwith food and oxygen

Food caught by the coral Food caught by the coral supplies both with supplies both with phosphorous and nitrogenphosphorous and nitrogen

Algae are crucial to calcium Algae are crucial to calcium carbonate depositioncarbonate deposition Without algae corals unable Without algae corals unable

to produce substantial reef to produce substantial reef structuresstructures

Complicates geochemical Complicates geochemical records from coralsrecords from corals

Coral Growth Polyps are seated in Polyps are seated in

aragonite secreted by the aragonite secreted by the epidermisepidermis CaCOCaCO33 is deposited is deposited

beneath living tissuebeneath living tissue Interconnected polyp Interconnected polyp

networks completely networks completely covers the skeleton covers the skeleton

Corals periodically Corals periodically encapsulate a portion of their encapsulate a portion of their skeleton and seal it off from skeleton and seal it off from contact with sea water or contact with sea water or living tissuesliving tissues Over the course of years, Over the course of years,

each polyp lifts itself each polyp lifts itself hundreds of times leaving hundreds of times leaving new skeleton behindnew skeleton behind

Annual Banding in Coral Density of skeleton depends on coral Density of skeleton depends on coral

growth rategrowth rate Related to temperature and cloud Related to temperature and cloud

covercover Winter growth slow and skeleton is Winter growth slow and skeleton is

dense (dark)dense (dark) Spring and summer growth rapid Spring and summer growth rapid

and skeleton is less dense (light)and skeleton is less dense (light) Seasonal coral banding may be visible Seasonal coral banding may be visible

to the naked eye or apparent in an x-to the naked eye or apparent in an x-ray ray

Age of corals determined by counting Age of corals determined by counting bandsbands Uneven banding can reveal Uneven banding can reveal

significant weather eventssignificant weather events

Sample Collection

Hydraulic drill Hydraulic drill used to collect a used to collect a core through core through the coralthe coral

Cores taken to Cores taken to coral's plane of coral's plane of maximum maximum growthgrowth

Coral Records of SST 1818O function of SST and O function of SST and

salinity (fresh water influx salinity (fresh water influx and precipitation)and precipitation)

Close correspondence Close correspondence between between 1818O and O and instrumental measurements instrumental measurements Red spikes in Red spikes in 1818O record O record

match up with red spikes match up with red spikes in the SST recordin the SST record

Coral Coral 1818O data nearly as O data nearly as accurate as instrumental accurate as instrumental datadata

Coral records can cover the Coral records can cover the past 500-800 yearspast 500-800 years

Instrumental records are only Instrumental records are only available for the last 50-100 available for the last 50-100 yearsyears

Long Records Detailed records of Detailed records of 1818O provide information O provide information

on SST and El Nino activity for last 350 yearson SST and El Nino activity for last 350 years Longer records obtained by splicing recordsLonger records obtained by splicing records

Other Coral Geochemical Proxies Cd/Ca and Ba/Ca proxy for upwellingCd/Ca and Ba/Ca proxy for upwelling

Cd and Ba have nutrient-like distributions in Cd and Ba have nutrient-like distributions in seawater and therefore are sensitive seawater and therefore are sensitive indicators of vertical mixing -- Other proxies?indicators of vertical mixing -- Other proxies?

Terrigenous Material in Marine Environments

Weathering and erosion processes in Weathering and erosion processes in different climatic zones on continental land different climatic zones on continental land masses produce characteristic inorganic masses produce characteristic inorganic productsproducts

Those products are transported to oceans Those products are transported to oceans (wind, rivers or floating ice) and deposited on (wind, rivers or floating ice) and deposited on the sea floorthe sea floor Carry information about the climate of Carry information about the climate of

their origin or transportation route, at the their origin or transportation route, at the time of depositiontime of deposition

Terrestrial detritus dilutes the relatively Terrestrial detritus dilutes the relatively constant influx of calcium carbonateconstant influx of calcium carbonate Most basic information is carbonate purityMost basic information is carbonate purity

Terrestrial Sediments Several types of non-marine sediments Several types of non-marine sediments

can provide relevant climatic informationcan provide relevant climatic information Aeolian, glacial, lacustrine and fluvial Aeolian, glacial, lacustrine and fluvial

deposits are a function of climatedeposits are a function of climate Often difficult to distinguish specific Often difficult to distinguish specific

causes of climatic change causes of climatic change Erosional features such as ancient Erosional features such as ancient

lacustrine or marine shorelines, or glacial lacustrine or marine shorelines, or glacial striae also reveal climatic informationstriae also reveal climatic information

Periglacial Features Morphological features associated with Morphological features associated with

continuous (permafrost) or discontinuous continuous (permafrost) or discontinuous (diurnal or seasonal freezing) periods of sub-(diurnal or seasonal freezing) periods of sub-zero temperatureszero temperatures Features such as fossil ice wedges; pingos; Features such as fossil ice wedges; pingos;

sorted polygons; stone stripes; and sorted polygons; stone stripes; and periglacial involutionsperiglacial involutions

Climate reconstructions are subject to a fair Climate reconstructions are subject to a fair degree of uncertaintydegree of uncertainty The occurrence of periglacial activity can only The occurrence of periglacial activity can only

indicate an upper limit on temperaturesindicate an upper limit on temperatures These features are difficult to dateThese features are difficult to date

Dating of associated sediments provides Dating of associated sediments provides only a maximum age estimateonly a maximum age estimate

Glacial Fluctuations Glacier fluctuations result from changes in Glacier fluctuations result from changes in

the mass balance of glaciersthe mass balance of glaciers Glacial movements lag climate forcingGlacial movements lag climate forcing Different glaciers have different response Different glaciers have different response

times to mass balance variationstimes to mass balance variations Interpreting glacial movements in terms of Interpreting glacial movements in terms of

climate complexclimate complex Many combinations of climatic conditions Many combinations of climatic conditions

might correspond to specific mass balance might correspond to specific mass balance fluctuationsfluctuationsTemperature, precipitation (snowfall) Temperature, precipitation (snowfall)

and wind speed are three main factors and wind speed are three main factors

Records of Glacial Movements Record of glacial front movements is Record of glacial front movements is

derived from morainesderived from moraines Piles of sediments carried by Piles of sediments carried by

advancing glaciers and deposited advancing glaciers and deposited when they retreatwhen they retreatPeriods of glacial recession, and the Periods of glacial recession, and the magnitude of recession, are harder magnitude of recession, are harder to identifyto identify

Repeated glacial movements can Repeated glacial movements can destroy evidence from earlier destroy evidence from earlier advancesadvances

Dating Glacial Movements Dating glacial movements prone to Dating glacial movements prone to

considerable errorconsiderable error Radiocarbon dates on organic material in Radiocarbon dates on organic material in

soils on moraines provides a minimum age soils on moraines provides a minimum age for glacial advancefor glacial advanceConsiderable time lag may exist Considerable time lag may exist

between moraine deposition and soil between moraine deposition and soil formationformation

Lichenometry (lichens) and tephrochronology Lichenometry (lichens) and tephrochronology (lava flows) can sometimes be to date glacial (lava flows) can sometimes be to date glacial eventsevents Reliability is restrictedReliability is restricted

Lake Level Fluctuations In regions where surface water discharge (via rivers In regions where surface water discharge (via rivers

and other waterways) is restricted to inland basinsand other waterways) is restricted to inland basins Changes in the hydrological balance can provide Changes in the hydrological balance can provide

evidence for past climatic fluctuationsevidence for past climatic fluctuations In land-locked basins, water loss is almost In land-locked basins, water loss is almost

entirely due to evaporationentirely due to evaporation•During times of positive water budgets During times of positive water budgets

(wetter climates), lake levels rise and lakes (wetter climates), lake levels rise and lakes expandexpand

•During times of negative water budgets During times of negative water budgets (drier climates), lake levels drop and the (drier climates), lake levels drop and the aerial expanses recedeaerial expanses recede

Lake studies particularly useful in arid or semi-arid Lake studies particularly useful in arid or semi-arid areasareas

Lake Titicaca, Altiplano, Andes What can the lake level of high altitude lakes tell us What can the lake level of high altitude lakes tell us

about oceanic circulation and atmosphere-oceanic about oceanic circulation and atmosphere-oceanic interactions?interactions?

R/V Neecho, WHOI

Salar de Uyuni, Bolivia World's largest salt flat contains a record of alternating wet/dry World's largest salt flat contains a record of alternating wet/dry

periods on the Altiplanoperiods on the Altiplano

Factors Affecting Lake Level Factors affecting the rates of Factors affecting the rates of

evaporation includeevaporation include Temperature, cloudiness, wind speed, Temperature, cloudiness, wind speed,

humidity, lake water depth and humidity, lake water depth and salinitysalinity

Factors influencing the rate of water Factors influencing the rate of water runoff includerunoff include Ground temperature, vegetation Ground temperature, vegetation

cover, soil type, precipitation cover, soil type, precipitation frequency, intensity and type (i.e. rain, frequency, intensity and type (i.e. rain, snow etc.), slope gradients and stream snow etc.), slope gradients and stream sizes and numberssizes and numbers

Identifying Lake Levels Episodes of lake growth identified byEpisodes of lake growth identified by

Abandoned wave-cut shorelines, Abandoned wave-cut shorelines, beach deposits, perched river deltas beach deposits, perched river deltas and exposed lacustrine sediments and exposed lacustrine sediments

Episodes of lake retreatEpisodes of lake retreat Identified in lake sediment cores or Identified in lake sediment cores or

by paleosols and evaporites by paleosols and evaporites developed on exposed lake beddeveloped on exposed lake bed

Stratigraphy, microfossil analysis and Stratigraphy, microfossil analysis and geochemistry may be used to decipher geochemistry may be used to decipher lake level historylake level history

Pollen Analysis Pollen and spores Pollen and spores

accumulationsaccumulations Record past vegetationRecord past vegetation Changes in the vegetation of Changes in the vegetation of

an area can be due to an area can be due to changes of climatechanges of climate

Pollen grains and spores form Pollen grains and spores form ideal recordsideal records Extremely resistant to decayExtremely resistant to decay Produced in huge quantitiesProduced in huge quantities Distributed widely from their Distributed widely from their

sourcesource Can possess unique Can possess unique

morphological characteristicsmorphological characteristics

Problems with Pollen Differences in pollen productivity and dispersion Differences in pollen productivity and dispersion

rates pose significant problemsrates pose significant problems Relative abundances of pollen grains in a deposit Relative abundances of pollen grains in a deposit

cannot be directly interpreted in terms of species cannot be directly interpreted in terms of species abundanceabundance

Calibration of pollen abundance and spatial Calibration of pollen abundance and spatial distribution to species frequency is necessarydistribution to species frequency is necessary

Pollen is a wind-blown sediment Pollen is a wind-blown sediment Accumulates on any undisturbed surfaceAccumulates on any undisturbed surface

Sediments containing fossil pollen include peat Sediments containing fossil pollen include peat bogs, lake beds, alluvial deposits, ocean bogs, lake beds, alluvial deposits, ocean bottoms and ice coresbottoms and ice cores

When pollen is deposited in water, differential When pollen is deposited in water, differential settling, turbulent mixing and sediment settling, turbulent mixing and sediment bioturbation can bias recordbioturbation can bias record

Pollen Uses Pollen analysis usually allow only Pollen analysis usually allow only

qualitative reconstructionsqualitative reconstructions The climate was wetter/drier or The climate was wetter/drier or

warmer/colderwarmer/colder Sometimes it is possible to quantify Sometimes it is possible to quantify

climatic variations by the use of climatic variations by the use of individual indicator species rather than individual indicator species rather than total pollen assemblagestotal pollen assemblages The occurrence of plants that may The occurrence of plants that may

not be abundant but which are not be abundant but which are limited by specific climatic conditionslimited by specific climatic conditions

Sedimentary Rocks Marine sediments >100 my subductedMarine sediments >100 my subducted If sediments uplifted and exposed, can If sediments uplifted and exposed, can

be used to reconstruct past climatesbe used to reconstruct past climates As sediments become progressively As sediments become progressively

buried undergo lithification and buried undergo lithification and diagenesisdiagenesis Geochemical proxies must take into Geochemical proxies must take into

account chemical alterationaccount chemical alteration Record can be compressedRecord can be compressed

Climate Reconstruction – Rock Type Rock type provides valuable informationRock type provides valuable information

EvaporitesEvaporitesLithified salt deposits and evidence of dry Lithified salt deposits and evidence of dry

arid climatesarid climates CoalsCoals

Lithified organic matter and evidence of Lithified organic matter and evidence of warm, humid climateswarm, humid climates

Phosphates and chertsPhosphates and chertsLithified siliceous and phosphate material Lithified siliceous and phosphate material

and evidence of ocean upwellingand evidence of ocean upwelling Reef limestoneReef limestone

Lithified coral reef and evidence of warm Lithified coral reef and evidence of warm surface ocean conditionssurface ocean conditions

Climate Reconstruction – Facies Analysis

Investigates how rock type changes over timeInvestigates how rock type changes over time A formation consisting of a shale layer A formation consisting of a shale layer

interbedded between two sandstone layersinterbedded between two sandstone layersEvidence of a changing sea levelEvidence of a changing sea levelPotentially linked to climatic change (Potentially linked to climatic change (e.g.,e.g.,

glacial ice formation)glacial ice formation) Sedimentation rates, sediment grain Sedimentation rates, sediment grain

morphology and chemical compositionmorphology and chemical compositionProvide information on the climatic Provide information on the climatic

conditions at the time of parent rock conditions at the time of parent rock weathering weathering

Biotic Indicators Type and distribution of marine and Type and distribution of marine and

continental fossils within fossil-bearing continental fossils within fossil-bearing rocksrocks Principally limestones and Principally limestones and

mudstones, occasionally sandstonesmudstones, occasionally sandstones Microfossil type, abundance and Microfossil type, abundance and

morphologymorphology Paleotemperatures can sometimes be Paleotemperatures can sometimes be

derived from oxygen isotope analysisderived from oxygen isotope analysis