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Palaeo\(^3\)
Fribourg, image - Coggle Diagram
Palaeo\(^3\)
Fribourg
Climate System
- Sun Energy \(\to\) atmospheric circulation \(\to\) winds - ocean surface circulation \(\to\) variation temp. and density of sea water (THC)
- Earth rotation \(\to\) coriolis force (deflection to right/left in N/S hemisphere
coriolis is more import in closed basins
\(\to\) currents that transport heat to poles (eg Gulf) are always on western part of the basin (due to coriolis)
ocean circulation generally follows the wind direction (3% of energy from wind to ocean transfered)
\(\to\) ekman transport: water transport in 90° to wind and coriolis, deflection different with water depth
response times:
- Fast response
- Atmosphere (hours to weeks)
- Land surface (hours to months)
- Ocean surface (days to months)
direct influence from atmosphere
- Vegetation (hours to centuries)
- Sea ice (weeks to years)
- slow response
- mountain glaciers (10 - 100 y and faster)
- deep ocean (100-1500 y)
- ice sheets (100-10000y)
Radiation balance on earth
- N-hemisphere im sommer im deficit
- S-hemisphere im winter im defizit
\(\to\) hoch am äquator (positive), tief an polen (negativ), overall balanced
- heat ttransfer from low to high latitudes
atmospheric circulation (caused by sun energy)
- precipitation at low and high latitites (blue) & evaporation at mid latitudes (yellow)
- hadley cells: heat transportation from low to mid latitudes
- cyclones (low pressure system, anti clockwise) (left)
- clockwise (high pressure system, clockwise)
- rossby waves:
turbulences between easterlies and westerlies accross the polar front
ITCZ
\(\to\) variable patterns: ocean looked different in past
surface ocean currents
- surface divergence: water upwelling, linear = front systems
- surface convergence (sinking water, "eddies" (colcore - downwelling and warmcore - upwelling)
\(\to\) upwelling waters = nutrient rich
forces influencing water:
- wind (friction)
- internal friction (eddy viscosity)
- coriolis force
- horizontal pressure gradient
circulation patterns:
- surface gravity waves
- ekman transport
-inertia current
- geostrophic current
- divergence & convergence (eddies, front and gyre systems)
North Atlantic Current system
- Intense western boundary current (Gulf stream very warm and influences up to 600m deep)
- Less pronounces eastern boundary currents (coastal upwelling - coastal plancton pools)
- NAO = North atlantic oscillation (islandic low pressure system + Azores high pressure system oscillating)
- positive NAO Index: very high pressure at azores & very low pressure above iceland
\(\to\) more and stronger winter storm across AO, warm and wet winter in europe, cold and dry in greenland, East-US mild and wet
- negative NAO Index: weak high at azores, weak low at iceland
\(\to\) fewer and weaker winter storms, moist air in mediterranean, cold europe, cold air and snow in east-US, mild winter in greenland
Indian Ocean current system and monsoon
- january: warm & dry air southwards: NE Monsoon = Inter-Monsoon (ITCZ south of equator)
- july: SW Monsoon current: a lot of currents flowing away from africa
--> wet period
Pacific Ocean current System and ENSO
- El-Niño souther oscillation
higher sealevel in west (Australia) causes water to flow from west to east, which leads to reduced upwelling, due to warm water intake (which leads to more precipitation and brings temp. down) --> water flows from east to west, starting the cycle over again
- during El-Niño events:
Caracterization of water
- conservative tracers (major elements in salts)
- altered by processes occuring at the boundaries of the ocean (Sea-surface, sea-floor, continental shelves and slopes)
- Temp - Salinity
Temp: remains constant over time (conservation of energy), Very cold water (south arctic water mass) fills basin and is not mixing well with waters above
salinity: balance between input of salt and removal of sediments (water input influences salinity heavily though), PSU = practical salinity Unit (old)
- high evap. - more salinity (mediterranean sea has different volume and higher salinity in east due to evap)
\(\to\) higher salinity - higher density, high T, low density: Seawater density \(\sigma_{\Theta} = density \cdot (-1000)\)
- regular mixing laws
- Non-Conservative tracers (minor elements in salt)
- altered by physical, chemical or biological processes occuring within the ocean (eg mixing)
- Nutrients
- Fluorescence (for productivity)
- dissolved Oxygen
Cold water = high \(O_2\), the "older" the water, the less oxygen is available (decomp. and bacteria consume O2, photosynthesis on surface bring O2)
- isotopes/elements
- Chlorofluorocarbons (CFC's)
- Radiocarbon (\(^{14} C\)) "Age of water"
Temp and salinity, water masses mixing (Frontal systems)
- No mixing between 3 homogeneous water masses
- start of mixing
- strong vertical mixing
- Thermocline:
--> help determine water bodies
Thermo- pycno- and nutriclines
- strong monsoon warms the water and depleats it in nutrients, whereas weak monsoon has a higher thermocline with cold, nutrient rich water closer to the surface ( strong SE winds)
Seasons influence
- Winter: lowest sunlight and highest nutrient, isothermal temp throuout the depth
- Spring: increasing sunlight, decreasing nutrients, increasing thermocline
- summer: highest sunlight, lowest nutrients, strongest thermocline
- fall: decreasing sunlight, increasing nutrients, decreasing thermocline
\(\to\) delayed response
Elements in the Ocean
- occurrence, distribution and cycling of elements gives info about earth's life support system
- 7% of all elements (6) make up 99.3% of elements in the ocean (Cl, Na, Mg, S, Ca, K)
conservative elements
- residence time > 100'000 yr
Non-conservative elements
- variable residence time, but shorter (500-1500 yr)
residence time
\(\tau = \frac{Total \ mass \ of \ substance \ dissolved \ in \ the \ ocean}{Rate \ of \ Supply \ (or \ removal) \ of \ the \ substance}\)
Biogeochemical cycles
- recycling organic matter in the photic zone (3/4 above permanent termocline, 500-1000m), ¼ sinks into deep water , 1% to the seafloor (below 1000m mostly faecal pellets)
\(\to\) during blooming (high activity) a lot more is able to fall down
up to 4000m visible changes during bloom periods (thogh delayed)
Nutrients for organisms on sea floor
- organic compound (soft tissue (O, H, C, N, P))
- Inprganic compound (skeletal material (12CaCO3 *2SiO2)
\(\to\) dissolved organic carbon
Redfield ratio: C:N:P ~106:16:1 (accurate for above the thermocline?)
Data collection via sediment traps, mounted on a mooring line
POM (particulate organic matter) and nutrient cycle:
- residence time <10^6
- Bio limiting: P, N, SiO2
- Bio intermediate: C, Ca2+, Ba2+
POM and scavenging cycle
residence time: <100-1000 yrs
- Adsorption of metal ions onto particle surface (mainly bacteria, passive process)
- Scavenging: adsorption, capture and removal from the water column
\(\to\) passive processes
Water masses:
- Intermediate water masses:
AIW: Arctic intermediate water
MOW: meditteranean (outflow) water
AAIW: Antarctic intermediate water
- largest intermediate water mass
traced up to 30°N, low salinity (34.2), low temp (2-4°C)
- deep water mass:
NADW: cyclonic gyres in greenland and labrador seas main areas of deep water formation
salinity: 34.9, temp<0°C
fills basins and flows over sills (cascading)
\(\to\) the longer deep water travels, the more nutrient rich it gets - nutrient rich water at upwelling
\(\to\) upwelling dissolves carbonates, making the sediments more Si-rich
deep sea sediments
determined by:
- productivity of surface waters
- water depth (long travel to seafloor)
- supply of terrigenous sediment (dilution of biogenic components)
- solubilities ∞ chemistry of watercolumn for distribution on seafloor
Components
- Calcite (saturated before aragonite)
- Aragonite
- silicate
most (silica) material exported from the seasurface, gets not dissolved until it reaches the seafloor (dissolution mainly on seafloor, only 1-10% not dissolved!) - mainly siliceous below ccd
\(\to\) upper water undersaturated in silica, lower water undersaturated in carbonate
\(\to\) why not equally distributed on the seafloor? Biopackaging - marine snow - fecal pellets (bio aggregation)
Accumulation rates:
- terrigeneous: m/1000yr
- siliceous: cm/1000yr
- carbonate: cm/1000yrs
- deep-sea clays: mm/1000yrs
- CM sediments: dm/1000yrs
Lysocline: strong decrease in carbonate due to dissolving
in the future, marine species will be smaller due to higher pH in the seawater
\(\to\) saturation depth shallower today than in past
-
Stratified watercolumn
- Temp: varies horizontally with latitude, and with depth
- Vital life: in temp range 0-40°C, some up to 85°C or <0°C
\(\to\) permanent thermocline separates mixed layer at surface from intermediate and bottom water
- dissolved oxygen
- light
Photic zone (up to 200m)
dysphotic zone: not sufficient light for photosynthesis (200-1000m)
aphotic zone: no light reaches here (>1000m), Bioluminescence
\(\to\) distribution of nutrients and life
Nutricline: Zone of rapid nutrient change (associated with max in fluorescence)
Pycnocline change of density
W2, F57-63?
Paleooceanography
ocean floor max 180-200 myrs old
- at 80-100 myr max depth is reached, weight is gained (accumulation of sediments)
- at 180-200Myr crust is very heavy and able to subduct
\(\to\) Basin expands from initial rift until a subduction developes and the basin begins shrinking until complete closed
Sediment cores
- help reconnstruct evolution of basins, changing of contnents
- 2 main events: opening of drake passage (49-17Ma) and closing the isthmus of panama (15-4.5Ma)
- non-biologic (volcanic glass, Fsp, silt/mica, clay)
- siliceous microfossils ( diatoms, radiolarians, sponge spicules, silicoflagellate)
- calcareous microfossils ( coccolith, foraminifera)
use decision tree to determine lithology
- biogenic rich (Calcareous ooze - siliceous ooze)
- non-biogenic (red clays, terrigenous sediment, glaciomarine sediment)
- very dark color? organic matter, terrigenous input
Archives
- sedimentary outcrop (large area, exposed to weathering/erosion, layeres, sedimentary sequence)
- sediment core ( layered, sedimentary sequence, seismics needed to observe larger area)
- ice core (different composition and deposition and potential (air bubbles vs pore water, robust records of past climate)
--> for all: isotopes as proxies
→ älteste kontinentale sedimente bis zu 3.6 mrd yr, ozeanische sedimente nur bis max 200Ma
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Proxies
- microfossil assemblages (very useful and commonly used for lots of things)
- ecological preference, special environmental conditions (T, S, nutrients, Oxygen levels)
- Elements and isotopes (from biologic skeleton, organic matter or other sediment components)
→ Ideally, one Proxy correlates with only one variable
→ usually multiproxy approach!
Proxies used:
- Oxygen isotopes:
\(\delta^{18} O = \frac{\frac{^{18}O}{^{16}O}Sample \ - \frac{^{18}O}{^{16}O}Standard}{\frac{^{18}O}{^{16}O} Standard} \cdot 1000 \) [‰]
→Since \(^{16}O\) is lighter than \(^{18}O\), in periods of high evap and precipitation, \(^{16}O\) is enriched in glaciers/snow and the seawater is enriched in \(^{18}O\)
→Glacial-Interglacial cycles
- Carbon isotopes:
- indicator for productivity, charecteristic water mass
- in all carbonates and organic matter containing C present (Forams, corals, coccoliths, molluscs, crinoids,...)
\(\delta ^{13}C\) in benthic forams = \(\delta ^{13}C\) ratio of seawater
in sediments (tot organis/inorganic carbon TOC,TIC), in water dissolved organic/inorganic carbon DOC, DIC
→ Interferences: Photosynthesis, bio setting, Air-sea exchange, vital effects (species dependent), diagenesis
- Neodymium isotopes \(\varepsilon_{Nd}\)
- old CC has lower \(\varepsilon_{Nd}\) than younger mantle derives material
- residence time 300-1000 yrs
- used for ocean circulation
- non sedimentary Coral \(\varepsilon_{Nd}\) = \(\varepsilon_{Nd}\) in seawater
Test:
Paleoecology
- reconstruction of the biosphere through history
- ecology: scientific study of the interactions that determine the distribution and abundance of organisms
- taxa and biosphere have evolved over the last 4 ba
- uniformitiarianism can be applied to the basics
$- most species preserved in marine environment
Syntax:
- Paleoautoecology: functions and lifestyle of individual organisms
- paleosynecology: associations of communities
- Ichnology
- palobiogeography
- ecology (advantage: function and relationship of living organisms) \(\leftrightarrow\) paleoecology (limitations - preservation and alteration → taphonomy, advantage through time of species and communities)
- biosphere>Ecosystem>community>population>individual
→ each species occupies a niche with different important limiting factors, paleontology helps to shows the change of niches
Important factors (for niches)
- Light (autotroph vs heterotroph, photic zone ~200m in oceans)
- Nutrients (inorganic/organic, oligotroph vs eutroph)
- oxygen (OMZ, oxic - dysoxic - suboxic -anoxic)
- Temperature (poikilotherm and homeotherm)
- salinity (stenohaline and euryaline)
- sediment composition
- sedimentation rate and turbidity
- depth (CCD)
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Taphonomy
- only mineralized part fossilized (mostly)
- fossil represents only few % of living community due to physical fragmentation, chemical dissolution, bioerosion,...
- Lagerstätten = Deposit with very good preservation
Evolution
- earliest prokaryotes (Archean): oldest rock about 3.8Ba, major outgassing forms primitive atmosphere and oceans, cyanobacteria making Photosynthesis and creating stromatolites
- first Eukaryotes (Proterozoic): more complex, sexual reproduction, maybe associated to Oxygen increase, precambrian eukaryotes are acritarchs (planctonic cysts of algae 1.4Ba) = oldest marine organism with eukaryotic cells
→ in Neoproterozoic (1Ba) diversity of eukaryotes overtakes diversity of prokaryotes
- fisrt Metazoan (NeoProterozoic): still in debate, earliest potential metazoa (trace fossil) 1-0.7Ba, rising oxygen levels (from 0.1% to 1-3%)
- ediacaran fauna (ediacaran): major radiation of metazoa, rich and varied fauna (quartzite from australia), cnidaria most common fossil,Vendobiota (ediacaran garden, leaf shaped organisms), mostly epifaunal or semiinfaunal
- Precambrian - Phanerozoic: the great divide (the agronomic revolution (microbial mats in precambrian → vertical barraw and mixgrounds in phanerozoic)
- cambrian explosion: second major radiation, significant amount of oxygen, herbivory vs carnivory (predation may cause shelled animals), diversification and variety of new morphologies, 10 new phyla (??), 50% of classes and many orders exist, more complex reefs, trilobites/brachiopods/echinoderms and mollusks
Three great faunas
- Cambrian Fauna: trilobites associate to eocrinoids, brachiopods, etc (epifaunal suspensions feeder)
- Paleozoic fauna: brachiopods, bryozoans, Ostracods and Crinoids (epifaunal suspensions feeders and infaunal)
- modern fauna: bivalves, gastropods, echinoids, fishes, reptiles and mammals (great variety of lifestyles)
epifaunal = lives on the seabed
infaunal = lives in the substrate
Foraminifera:
- planctonic: ~50 species, large paleotemp reconstruction (isotopes), paleoproductivity
- deep sea benthic forams: glacial-interglacial, greenhouse climate (no ice caps on poles), paleocene-eocene ~56Ma and other peak-warm periods (Hyperthermals), K/Pg extinction, oceanic anoxic events
- benthic forams: widespread, thousands of species
- proxies:
Morphotypes: microhabitat, (infaunal/epifaunal) oxygenation, productivity
→ forams can partially show the living mode via its shape ( biserial = infaunal, trochospiral = epifaunal
→ great uncertainty though
Planctonic/Benthic ratio: paleodepth, dissolution, surface productivity
→ Planctonic forams not in coastal zones, planctonic dissolve before benthic, shallow water and more food = more benthic (low P/B below lysocline, high P/B in open ocean)
species % Abundance, species diversity: paleodepth, paleolandscape, oxygenation of bottom waters, productivity, seasonality of productivity, labile/refractory organic matter, paleoEcoQS (??), CaCo3
salt marsh forams: rates of sea level rise - transfer function
coastal forams: Eutrophication, pollution (last few centuries/Millenia), forams bio monitoring (FOBIMO) towards a standardized protocol for soft-bottom benthic foraminiferal monitoring studies
Test
- What is ecology and what is paleoecology?
- It is the present a key to the past?
- Which are the factors influencing the biotic distribution?
- Which are the main diversification events in the history of the earth?
- Modern foraminifera are paleoproxy for what?
Case study
carbon Cycles
- short term global carbon cycle
- primary factor in regulating climate can be observed in short term carbon cycle, its reservoirs and carbon transfer rates and processes from Major reservoir to reservoir (yearly process)
- residence time = \(\tau \ [yr] = \frac{Total_{Mass} \ [t]}{Rate \ of \ supply \ [t/yr]}\) - constant in steady state
- greenhouse effect: Energy from the sun = electromagnetic radiation: earth receives rel. short wavelengths and radiates back a longer wavelength. some gases absorb this long wavelength (reradiation) and warm further the surroundings (makes earth habitable) (effectivity O3> CH4> CO2>H2)
→increasing radiative forcing - increasing temp on earth (calculated relationship: general circulation models (GCMs); 2*CO2 → ø+1.25°C)
largest reservoirs:
- Lithosphere (liquid, solid, gas)
- deep Ocean + surface waters + dissolved organic carbon + marine organisms (gas, dissolved ions)
- Soil (solid and gas)
- Atmosphere (gas)
- Biosphere (gas & solid)
-
- recent/past changes in CO2
- examination of instrumental and icecore records of atmospheric CO2 levels
- saw toothed curve due to seasonal changes (N-Hemisphere: Winter = high CO", su mer = low CO2 (high Photosynthesis))
Ocean absorb high CO2 when high Phytoplankton acticity (Sea surface temp SSt also important)
→ pCO2 doubles with 16°C increase in sea water, upwelling of CO2 and nutrient enriched sea water, photosynthesis and respiration control [CO2] and alkalinity in surface waters
- Long term global carbon cycle
- carbon cycle and atmospheric CO2 accross the Phanerozoic (540Ma-0) using Proxy data (greenhouse vs icehouse world)
- Long term: Plate tectonics and weathering important (Lithosphere has 66'000-100'000'000 Giga tins of Carbon stored!
- Greenhouse vs icehouse: < 500ppm CO2 during widespread continental glaciations and <1000ppm during warm periods (Higher uncertainty for >430Ma)
test:
extreme environmental changes:
- todays climate in context of the past gives concrete observations from natural examples at different timescales
Ice cores from antarctica give high resolution CO2 records (not too far back!)
Warming extremes:
- Toarcian Ocean Anoxic event (T-OAE) ~183Ma
- Paleocene-Eocene Thermal Maximum (PETM) ~56Ma
→ both have a negative carbon cycle perturbation (N-CIE) - indicator of pulses of massive light carbon injections (volcanic, thermogenic or biogenic carbon) simplified: \( \delta ^{13} C= \frac{^{13}C}{^{12}C} -1 \)→ increased CO2 in atmosphere → global warming, ocean acidification, increased weathering,... → anoxia and organic matter burial, global environmental crisis
→ the increased weathering and ocean anoxia helps with decrease of CO" and then leads to recovery!
Ocean Anoxic event:
- Ocean largely depleted in O2
- ocean circulation & global climate rapidly altered
- major impact to carbon cycle
- T-OAE is the first, followed by multiple more throughout the jurassic and creatceous
→ often very good fossil preservation, implicatons for modern climate change, industrial importance, since this is a crucial source of oil
- Toarcian Ocean Anoxic event (T-OAE) ~183Ma
- start at 150Kyrs, duration ~300-900kyrs (onset + recovery)
- Karoo-ferrar Large igneous province (K-F LIP)
OM rich deposits (organic matter, thogh influenced by local conditions -> not worldwide visible OM, in jura mountains visible) -> black shales
Jura Mountains: Warm and humid conditions, enhanced continental weathering and detrital input
→ Extinction due to collapse of carbonate factory (benthic fauna), nektonic invertebrates (belemnite, ammonite), terrestrial fauna and flora
- global warming 3-7°C and environmental crisis
→ Recovery: organic carbon burial (european basins efficient, but not globally), increased continental weathering very efficient feedback mechanism
- Paleocene-Eocene Thermal Maximum (PETM) ~56Ma
- start: ~8-23kyrs, duration (150-220 kyrs (onset + recovery)
- coincidence North Atlantic Igneous province (NAIP)
- PETM in late paleocene, early eocene climatic optimum, eocene-oligocene cooling: start of modern iceage!
- multiple smaller hyperthermal events after the PETM recordes
- extreme and rapid episode of global warming (5-8°C) & environmental changes
- high latitude warming (extreme over antarctica) → impact on ocean circulation
- local-regional stagnant and anoxic oceans
- extinction: bottom dwelling deep-sea organisms, open ocean plancton, terrestrial mammals, important radiation of mammals (benthic forams extinction)
- recovery: localized marine anoxia (OM burial not efficient) → delayed recovery and persistence of warm conditions leading to warm conditions: eocene optimum?
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Future
PRISM = Pliocene Research, Interpretation and Synoptic Mapping
- How is Paleogeography, climate, sea level of early to mid-pliocene time (5-3Ma)?
- difference Pliocene - today:
today more icecover, higher sealvel (more lakes/islands in canada visible but also florida island more prominent-lower sealevel closer equator?) → influences isostasy!, differences in rain (river drainage, visible at new orleans) and carbonate platforms (due to less shallow regions near equator (florida)
- what region(s) appear most sensitive to climate forcing an why?
- regions in higher latitudes
- Eustatic (global) vs. regional sea level - why can both sea level rates differ?
- global Sea level today little lower than in pliocene and both today and pliocene a lot higher than during LGM
→ principle mechanisms: Ice volume, seawater temp (expansion with warmer water)
in the past 5 Myrs, deep sea \(\delta^{18}O\) Values show differences in frequency and amplitude
- eccentricity: value of the earths orbit and its difference to a perfect circle
- obliquity: angle of earths axis
- precession: how earth wobbles around its own axis
Pliocene warmth:
- global mean annual temp +2°C compared to today
- The IPCC predicts this warming for end of 21st century
- modern SST towards higher latitudes colder than in mid pliocene
- SST from mid-pliocene - present: Most change towards highest latitude, least change around equator
- temperature on land? From peat deposits (eg from canada) MAT (mean annual (air) temp) can be measured with following proxies:
- \(\delta^{18} O\) on fossil wood cellulose
- Annual tree ring width
- Coexisting paleovegetation
- Bacterial tetraether composition in paleosols (=ancient soils)
→ towards higher latitudes, air temp. also has the greatest change (15-18°C near poles)
→ in the early Eocene climatic optimum (EECO) towards high southern latitudes extreme warming
It seems, like modern day climate has a bigger overall difference in temperature: warmer equator and colder poles compared to plio- and eocene
- generally, CO2 concentration seem to have sunk constantly over time. Altough present pCO2 is pretty high compared to the pliocene (red bar shows present)
→Temp in pliocene warmer than today, pCO2 similar or lower than today
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