exam 1 Flashcards
curvature of earth
Affects intensity of light hitting the planned at any one point
causes light distribution, Coriolis, increased variations in photoperiod with higher latitudes, wind patterns
Orbit
Small changes over time (e.g. wobbling) causes changes in solar insolation (radiation that impacts climate change)
causes light distribution, Coriolis, increased variations in photoperiod with higher latitudes, wind patterns
Tilt
Causes seasonal changes
causes light distribution, Coriolis, increased variations in photoperiod with higher latitudes, wind patterns
albedo
reflexivity of earths surface, part of why Antartica is so cold
Total reflectivity: albedo =1
solstices
Solstices occur in June & December, edge of circle of illumination is around 66.33º causing polar circles to be 24 hr sunlight or darkness, depending on earth’s position in orbit; opposing seasons in northern vs southern hemispheres
equinoxes
Equinoxes occur in March & September, edge of circle of illumination passes directly through the poles, daylength = nightlength everywhere on the planet for that one day
solar & infrared radiation
Some solar radiation is lost or reflected back to space from earth’s surface. Some is absorbed at surface, radiated back to atmosphere as infrared radiation (IR)
Greenhouse gases (CO2, CH4, O3) trap IR, warming the planet (necessary for life)
North Pole vs south pole
receive the same amount of solar radiation just at different times of year
temp of North Pole (arctic)
-why
-18 C bc of oceans breaking up arctic sea ice in the summer
Antarctic (South Pole) normal temp
-why
-52 C bc its a continent with ice sheets (high albedo) and high elevation (4000+ m)
Antarctic ice & precip
<2% ice-free lan, 2-4 km thick ice sheets, interior of the continents gets <2” of precipitation (cold-desert)
-little snow that falls on cold desert doesn’t melt and accumulates over time
Antartica plants and animals
only two flowering plants and only on the antarctic Peninsula, no fully terrestrial vertebrates (only few inverts)
why study Antartica?
1) Helps understand the fossil record, paleobiogeography, plate tectonics
2) Development of Earth’s climate (past & present)
3) Last relatively pristine place on Earth
4) Evolution of species in extreme conditions
5) Human presence is growing, future resource interest
6) Vital for climate change & sea level rise information (now & future - 70% of Earth’s freshwater is trapped in ice)
7) Fascinates imagination due to its extreme condition and remote location
plate tectonics
Plates on the planet move independently of each other, due to the movement of the asthenosphere under the lithosphere
Rodinia
supercontinent that formed 750 mya, SWEAT hypothesis suggests it once included western NA and east Antarctica by granites
gondwana
southern supercontinent (warming period cause oceans to become very acidic possibly causing marine loss, lots of vegetation) 550 mya
pangea
supercontinent that formed from the northern and southern continents, carboniferous ice sheet 300 mya
radioactive isotopes
change atomic # and mass at a constant decay rate
stable isotopes
remain stable with fixed number of protons of the same element, but each isotope has different number of neutrons and mass.
-stable oxygen isotopes are extremely useful in determining past temperatures
igneous
from liquid magma to solid rock as they cool
-basalt, granite
sedimentary
accumulation of pieces of other rocks that fuse together, can see layers, impressions, fossils
-sand stone, siltstone, limestone)
metamorphic
changed rock from melting/pressure
-schist marble
continental crust
less dense but thicker
-up to 35 km thick
made of granite
oceanic crust
denser but thinner -6km made of basalt
lithosphere
solid but elastic, broken up into plates, including the continents, and move about asthenosphere
asthenosphere
liquid magma layers that causes plate movement
-hot spots can break through lithosphere creating island chains
divergent boundaries
spreading plates away from each other (most underwater),
-forms new continental crust as they spread
caused by mantle convection
convergent boundaries
colliding plates, one subducts or goes under the other, can cause uplift
-form mountain ranges/earthquakes
cause day mantle convection
transform
plate edges grinding past each the run opposite directions
caused by mantle convection
rifting
lithosphere stretches causing the continental crust too thin. Asthenosphere rises
-Volcanoes/fault escarpments
SWEAT hypothesis
Southwest - East Antarctica connection. When Rodinia was a supercontinent eastern Antarctica and western North America were connected. Based on isotopic geochemistry of equivalent granite found in both places. The isotopic composition developed when the rock formed.
glossopteris
fern-tree, fossil leaf impressions in sedimentary rock from Mt. Wild on Antarctica (255 mya). Also found in India, Australia, South Africa and South America
-evidence for continents once being connected, supporting plate tectonics
lystrosaurus
therapsid dicynodont reptile that survived mass extinctions found in Africa, Antarctica, European Russia & Mongolia by Edwin Colbert
-evidence for continents once being connected, supporting plate tectonics
thrinaxodon
cynodont therapsid found in Antarctica and Africa
-evidence for continents once being connected, supporting plate tectonics
when did Gondwana break up
started 180 mya finally Antartica split 32 mya when the South Antartica Peninsula
impact of gondwana
drakes passage and forming the circumpolar current which initiated cooling (ice started to form) and isolation of the Antarctic continent
jurassic period dinosaur fossils found on antartica
180 mya
cryolophosaurs, long-necked sauropods, mosasaurs, plesiosaurs, etc).
what caused the breakup of Gondwana
mantle blumes
antarctic circumpolar current
only current that flow around the globe in southern hemisphere
-helps isolate antartica
microplates
Tectonic plates too small to track, positioned themselves as part of Antarctica such that the Ellsworth Mountains w/ anomalous orientation when Gondwana broke up
transantarctic mountains
(divides east & west Antarctica), and they sit on a plate boundary.
-above sea level
Ellsworth mountains
sit on a micro pate
when did the ice sheet start, and reach, thickness
started 32 mya
-sediment cores at Prydz Bay have glacial boulders and pebbles carried by glaciers and deposited in bay by then.
Reach current size/dimensions by 14 mya
ice sheets thickness and area
4km thick and cover 14 million km^2
how does the weight of the ice sheet affect the continenet
pushes it down but when glaciers melt isostatic uplift occurs
-evidence in raised beaches, former beaches w/ water-worn cobble/pebbles
how much of earths freshwater is in antarctic ice sheet
60-80%
how high would sea level rice if antarctic ice sheet melted
60-70 m
what does antarctic ice sheet sit under
burried mountain ranges
west antarctic ice shet rests on rock below sea level
cryolophosaurus
“forzen crusted Dino”
proved antarctic was a forestproof of Gondwana that Ned Colbert found in the 1960’s
when did penguins evolve
61 mya
dry valleys
ice free sedimentary rock place
-lots of paleontology done there
crevasses
as glaciers melt more heat is absorbed which can open crevasses
-very dangerous and difficult to see and navigate
moraines
blodzoed dirt
lateral: on the outsides
medial: in the middle where two come together
terminal: at the bottom where they’ve converged and where they’re pushing dirt in front of them
glacial stratiations
as a glacier moves over rock below it will smooth and polish them. leaves akas in the rock indicating direction of glacial flow
glacial erratics
rocks that fall onto a glacier and become deposited in an entirely new area when the glacier melts
-coloration and type of rock often doesn’t match the geology in the new area causing them to stand out
ice regulation
when the bottom of a glacial melts under pressure, and refreezes when the pressure is relieved
dialectic sediment
poorly sorted sediments with particles ranging from clay size to boulders.
ice rafted debris
dirt and rock trapped in a glacier that gets carried to sea and then melts, depositing the debris into the marine sediments
interglacial sediment
silts that are trapped, not debris
when were glaciers and the east Antarctic ice sheet at the Prydz Bay and the Ross Sea
35 mya
ice shelf
glaciers that extended out into the ocean. they can grind along the bottom (some are free floating) of the ocean when they advance, leaving evidence wfor when they retreat
-ross sea ice shelf is massive and due to glacial convergences. it’s 100 ft above the water line which is only half as much as below it
ice tounges
caused by the rapid extension of glaciers into the ocean they constantly calve off, but are reformed from behind
-Drygalski Ice Tongue
ablation
when a glacier calves off (bringing debris) and can break away. Occurs naturally and constantly as a glacier pushes from behind. Includes evaporation from the surface and surface melting/runoff.
nothofagus trees
Two warming periods, one from the late Miocene to 15 mya and the other from the early Pliocene 5.3 mya to 1.8 mya caused tundra-like growth and dwarf Nothofagus trees to grow. Fossils of the tree were found in the Sirius Formation in the Transantarctic Mountains.
cape irizar
Located next to the Drygalski ice tongue in the Ross Sea, where as snow cover melted, a preserved penguin breeding site was revealed. The breeding site was so well preserved it appears to be only recently abandoned. It may have been abandoned due to food changes or snow coverage.
why is antarctic the colder, driest, and windiest place on earth
It is the coldest place due to maximum tilt away from the sun and high albedo. The high albedo perpetuates cold conditions as does the elevation above sea level and thick ice sheet that covers the continent. Dryness is due to the constant high pressure from the polar cell, preventing storms from bringing in moisture. Also, cold air holds less moisture.
topography and temp relationships
Some areas are colder than others due to their topography. Inexpressible Island is one of the coldest due to winds coming off of two glaciers behind the island. Air flows downward all around the continent (channeled by valleys and coriolis force).
katabatibc winds
Katabatic winds form due to cold dense air rapidly moving down valleys (in part due to gravitational force) off the polar plateau with relatively warmer, less dense air above it (creates a pressure difference). These winds can help cause sea ice formation over coastal waters, and open-water areas surrounded by sea ice (polynyas). They are especially strong in summer due to the cold surface air on the ice.
how to katabatibc winds affect antartica
strong windchill which affects local climate, sea ice formation, and movement and erosion, and penguin behavior
ventifacts
rocks and boulders that are sculpted by blowing ie crystals and sand
saltation
winds lift sand particles up which are then pulled down by gravity, forming a ballistic path. these particles blast pits into rock.
sastrugi
drifts in snow caused by erosion, wind, and saltation. sastrugi are formed parallell to the wind.
antartic peninsula climate
- peninsula up to 50 cm of rain due to receiving warm air currents from the west
- temp 1-2 degrees C in Jan.
- two flowering plants there
- peninsula is more affected by climate change (more melting)
pathways for sea ice formation in rouch ocean
- frazil ice
- pancake ice
- rafting/ridging
- cementing/consoliation
=rough bottomed ice sheet
pathways for seaice formation in calm ocean
- frazil ice
- grease ice
- nilas
- rafting
- congelation ice
=smooth bottomed ice
frazil ice
freshwater ice crystals that form and move to the surface at the end of summer (March). winds from the continent and evaporative cooling at oceans surface reduces the water temp an dice begins forming at -1.8 degrees c and average salinity
what is avg salinity
35 ppt
freezing point of frazil ice
-1.8
grease ice
forms from frazil ice in calm waters. looks like dark stains on the water surface and lightens with development.
nilas
sheets that form from grease ice and cover the oceans surface as a thin layer
rafting and congelation
rafting occurs when currents or light winds cause nilas to slide over each other. the ice thickens into a smooth-bottomed ice sheet. pockets of waltwater (brine and algae within) get trapped as the ice congels
pancake ice
circular sheets of ice that form from frazil ice in rough waters. these can raft/ridge (ice bends o fractures and piles on itself) before consoliation
fast ice
newly formed sea ice that’s attached to land
drift ice
not attached to land
pack ice
ice drfit packed together by winds
ice floes
large pieces of drift ice
young ice
The younger the sea ice the thinner it is. New ice can form between pieces of old ice which causes rafting/ridges on old ice that occurred during formation. New ice is not drinkable (due to brine).
multi year ice
Multiyear ice is over a year old, thicker from congelation on bottom so not always breakable by an ice breaker, but melt water is drinkable as the congelation/compression gets rid of brine. More snow coverage limits light penetration.
how does sea ice stimulate the food chain
When brine gets trapped in the ice the algae within it lays dormant in the winter darkness, but begins growing in the ice with spring light from a greenhouse effect in the ice helping algal growth. This algae is released into the marine food web in summer when the ice starts to melt and stimulates the food chain (more ice = more algae).
thermohaline circulation
as ocean water becomes colder and more saline, it becomes more dense and sinks, creating circulation
water tempearture, salinity and density
Removal of fresh water from the ocean surface when sea ice forms causes water below to be very cold and more saline, so it becomes very dense and sinks.
antarctic convergence
The Antarctic Convergence is where cold surface waters moving northward form Antarctica meet warm waters, causing the cold waters to sink (more dense). The air temperature changes dramatically as you cross the convergence.
antartic divergence
The Antarctic Divergence is between the west wind drift and the east wind drift closer to the Antarctic continent.
antarctic coastal current (east wind drift)
This current is flows counterclockwise around the coast of Antarctica, driven by katabatic winds and coriolis force.
circumpolar deep water
Not cold when it comes to the surface due to warm sources (along with poles), and forms an area of open water surrounded by ice (polynya)
antarctic bottom water
Comes from the cold saline water that forms under ice sheets, sinks and moves along the bottom.
antartic circumpolar current (west wind drift)
This current keeps Antarctic isolated and travels around the entire globe. It is driven by prevailing westerlies (due to the low pressure system) and circulates clockwise around the entire continent. It is the only ocean current that encircles the globe.
ice shelves and grounding lines
Ice shelves are extensions of glaciers into the ocean. They have a hollowed out area below that forms due to warm circumpolar deep water flowing into the front face. They calve off due to ablation and ice sheets form in the front.
As ice shelves move they grind along the bottom creating moraines. Grounding lines are formed from these moraines and help to map ice shelf movement.
tabular iceberg
these are icebergs that are flat-topped because they have broken off of ice shelves
what does the penguin fossil record indicate about the now closed off ross sea
the area was open water until 27,000 BP until the ice shelf began advancing
what happened to the ross ice shelf in 2002
two huge pieces of the iceshelf broke off blocking currents in the southern ross sea and causing extensive sea ice coverage. This prevented deep water upwelling and changed ocean dynamics. Penguin colonies that needed open water access to breaches were nearly abandoned until the bergs broke up and open water returned.
Larsen B ice shelf
Located on the west Antarctic Peninsula it began breaking up in 2002. The rapid collapse was due to climate change and indicates that the peninsula is more affected by climate change than East Antarctica.
open ocean polynya formation
highly productive and are formed via warm water upwelling in a localized area
coastal polynya formation
formed by katabatic winds pushing sea ice away from coast
sensible heat
adding heat to change the conditions
-open ocean polynyas
latent heat
maintaining heat
-coastal polynyas
sea ice factory
katabatic winds are constantly cooling the ocean surface (enhancing ice formation) but are also blowing away the newly formed sea ice allowing more sea ice to form.
-occurs in coastal polynyas
terra nova bay polynya
A coastal polynya that formed from winds coming off the polar plateau. It persists through the winter and has allowed open water and beach access for breeding penguins for thousands of years in the Ross Sea
what are stable isotope ratios of oxygen in water useful for and why
Stable isotopes ratios of oxygen in water are especially useful as a proxy for past temperatures (H & ) have stable isotopes
how do stable isotope ratios of oxygen in water useful for proxy temps of the past
water evaporates from cold periods and is deposited and stored in glacial ice on land, leaving more o the heavier 180 isotopes in the ocean. Reverse occurs in warm periods
isotope ratios & per mil Change
the ratio of heavy to light isotopes compared to a standard x 1000, measure per 1000 (per mil), not per 100 as in percentage
Oxygen isotopes vs temperature and latitude
Concentration of 180 ions in precipitation decreases with temperature and from the equator to the poles
oxygen isotopes vs interglacial and glacial periods
Colder periods show an increase in the light oxygen isotope in the ice and increases heavy isotope in the oceans indication a smaller ratio. Warming periods see the reverse indicating a larger ratio
Ideal drilling site for ice cores
where the ice is the thickest and has the least amount of ablation. This is usually in the middle of the plateau and the flattest area with the least amount movement
annual layers in ice cores summer vs winters
Summer: layers are lighter due to larger grain size that don’t pack as closely as a result
winter layers: darker because the grains are smaller and light is reflected differently
ice core aging
- you can count annual rings (summer or winter)
- you can use known volcanic ash, dust, or other signature that have been dated elsewhere
- you can use dust with radioactive uranium isotopes with a known decay rate
dome c ice core
oldest ice core dated at -800,000 years old. There may be older ice cores dating back around 1,500,000 years in East Antartica
trace gasses in trapped air
CO2 is a proxy for past air temperature and can reflect changes in plant biomass
Methane (CH4) can reflect amount of wetland decay in warmer periods
N2O Can reflect soil microbial activity
Compared to earths atmosphere today
-all increase as temp increases
what is earths atmosphere today
78% N
21 % O
.035% CO2,CH4,H2O
greenhouse effect
solar radiation is mostly lost or reflected. the solar radiation that enters earths atmosphere is absorbed at the surface, then radiated back to the atmosphere as infrared radiation. The heat in this radiation is trapped by trace gases. This creates a warm blanket over the planet and is necessary for life. Increasing trace gases means more heat is trapped, increasing global termpatures.
CO2 in Earth’s History
CO2 in ice cores provides a glimpse into the past and how gases changed in the atmosphere naturally over time.
Warming and cooling cycles are due to solar radiation cycles (CO2 traps IR…
CO2 in past 800,000 years
there have been cycles of increases and decreases due to natural climate change.
we are in a cycle of rapid temperature increase that is occurring too fast for most organisms to adapt/evolve to cope with change.
Mauna Loa CO2 Record and trends
Has one of the longest modern records of measuring CO2 in the atmosphere (since 1958).
The site is good because it minimizes human contamination and is at a high elevation.
Annual cycles of increase and decrease are due to seasonal change (little to no photosynthesis in the winter).
Record shows that the amount of CO2 in the atmosphere today is increasing rapidly.
solar insolation, orbital forcing, wobbling
There is natural warming and cooling from slight changes in solar radiation caused by the Earth’s elliptical orbit and wobbling around the sun, which results in slight changes in solar radiation reaching the Earth’s surface. Insolation is another name for radiation. Cycles of climate change from this are now known in cycles of
41,000, 100,000, 400,000 years.
glacial cycles affect on sea level
Sea level drops with glacial periods (colder)
CH4 varies with CO2
bipolar see saw in climate
Two hemispheres see opposite trends in climate change over time. This is due to the north having more glacial (freshwater) discharge into the ocean which causes different responses in ocean/global currents there. For example some places will warm and others will cool as a response to changes in ocean currents and gyres
International Geophysical Year
The international geophysical year began in 1957-1958 with 67 countries participating at the end of the cold war. Sputnik 1 was launched by USSR in 1959. Knowledge was gained about how magnetic fields interact with/prevent comsic rays and solar winds.
why was Antartica good research location for space
due to lack of atmospheric interference. Early studies were focused on magnetic fields, cosmic rays and development of communications.
We now have a better understanding of the different atmospheric layers, interactions, and solar events.
earths magnetic field
the field exists due to earths solid iron core surrounded by liquid magma. the magnetic poled reverse every million years or so. Early research focused on navigation at sea, later interests developed on radio waves for communicaiton
magnetic poles and importance
the poles reverse every million years or so. they migrate up to 40 miles/year due to constant movement of the magma.
compasses are never exact due to this movement
stratosphere
temerpature decreases as altitude increases but it increases as the ozone layer because ozone traps heat
ionosphere
temp increase at this layer. this is where auroras occur due to charged particles being accelerated outward into upper atmosphere
aurora australis and causes
occur in the ionosphere due to charged particles being accelerated outward to upper atmosphere
instrumentation in antarctica
Antarctica is a good place to deploy instrument because of it’s large polar plateau across latitudes and once they are up there there is minimal interference
astronomy in Antarctica and why it is an ideal location for space telescopes
Antarctica is ideal for telescopes due to the extreme cold
1) The cold prevents water vapor in the air that would distort view
2) Reduced interference of infrared radiation from ground to scope due to high albedo
3) Reduced aerosols/pollutants
4) No light pollution
5) The stable bedrock means there’s little seismic activity
Telescope set up at South Pole station in the 1970s gives us some of the best images of cosmic/solar events. Gave us a better understanding of cosmic rays.
neutrinos
neutral subatomic particles that originate with radioactive decay, emitted from nuclear reaction in the sun, or from black holes.
Need a large array to detect the particles making the Antarctic environment ideal.
they help to understand process in the sun as well as early universe after the big bang
Cherenkov radiation
when neutrinos interact with ice to produce a blue flash
iceCube telescope
followed the AMANDA model (built in the 1990s) It was build between 2005-2010 for hundreds of millions of dollars at South Pole station to detect neutrinos
meteorites in antartica and patters in discovery
information they provide
They were first discovered in Antarctica in 1911 (1000s found since). They preserve extremely well in ice. They’ll melt down into moving glaciers, and bubble up to the surface when they hit a mountain range (Transantarctic Mountains). They stand out very well on the white surface forming meteorite fields.
They provide information on the moon, mars and how asteroids form.
ozone, where it came from how it’s formed/destoryed naturally
O3 molecules are constantly forming & breaking apart in the stratosphere 15-25 km above the surface and react with UV light.
O2 -> 2O O3 -> O2 + O
O + O2 -> O3 O + O3 -> 2O2
(formed) (destroyed)
Early earth’s atmosphere lacked ozone and any protection from UV rays so there was no terrestrial life. About three billion years ago marine life began evolving deep in the ocean (safe from the UV). It took 2.5 billion years for enough O3 to accumulate in the atmosphere to establish an equilibrium of O3 being created to O3 being destroyed which protected the surface enough from UV light to allow terrestrial life to evolve.
CFCs and chemical process of ozone depletion
CFCs breakdown in polar stratospheric clouds. In the winter clouds form with ice crystals at -78ºC. CFCs and N2O bind to the ice crystals and remain there through the winter.
In the spring the ice melts and the chemical reaction occurs releasing free Cl. The chlorine reacts with O3.
ClO + O2 -> Cl + 2O2
2O3 -> 3O2
One chlorine atom breaks down 100,000 O3 molecules before washing out of the atmosphere.
stratospheric clouds
form above Antarctica every winter in extreme cold and darkness, formed of ice crystals that capture CFCs and hep release free chlorine in the spring that destroys ozone
ozone hole and why only above antarctica
Antarctica is the idea place for cfc to breakdown due to extremely cold temps and stratospheric clouds that are not in the arctic. the ozone hole is technically a thinning of the ozone, not an actual hole.
Halley station ozone record
the ozone decline started in 1985. The station was founded during IGY. They sent balloons up to measure ozone and noticed a decline in 1977. Around the hole that would form in the spring/early summer they found chlorine (not a naturally occurring element in the atmosphere)
drakes passage
body of water between south America’s Cape Horn and south shetlands islands of antartica
evidence for cooling at 14 may
Decrease in CO2, ocean currents, ice dated back 500,000 years (some 1 mya under dry valleys)
Organisms found during the warming period were no longer found in fossil record past this point
Seymour island and penguin fossil record
Island located at tip of the Antarctic Peninsula, sedimentary rocks extensive, snow-free, lots of erosion (see lots of marine fossils)
Earliest penguin-like fossil from Palaeocene in New Zealand (61 mya), evolved in the southern hemisphere from a flying ancestor
15-20 fossil species on Seymour Island (fully formed, some 6 ft tall), Eocene or 50 mya
Seymour fossils indicate niche for penguins was established in the Southern Ocean by Eocene, marine ecosystem must have been highly productive/rich to support the diversity of penguins at that time
Gap in penguin record until Miocene (10 mya), diverse record in South America
