unit 9

Ozone in the STRATOSPHERE

absorbs UV-C and most UV-B radiation

-without this ozone layer, life on land would not have been possible due to too much raditation

-prevents skin cancer and cataracts caused by these

Ozone in the TROPOSPHERE

-respiratory irritant

-damaging to plant tissue

-pecurser to photochemical smog

how ozone absorbs UV-C and UV-B

UV-C breaks O2 into two free O atoms, which then combines with O2 = O3

UV-C also reverses this reaction by breaking them into O2 and O

-continued formation and breakdown of O3 in stratosphere absorbs all UV-C and most UV-B

CFCs (chlorofluorocarbons)

-primary anthropogenic cause of O3

-used as refrigerant chemicals and propellants in aerosol containers

-UV radiation frees the Cl atom

-highly electronegative Cl atom bonds to O3

-Free O atom bonds to chlorine monoxide to form O2 and FREE Cl ATOM to repeat cycle

-single Cl atom can persist in the atm. for long periods and destroy thousands ozone molecules

polar stratoshperic clouds

-natural Ozone depletion

Antartica spring melt forms PSC

-in presence of PSC, chlorine nitrate and hydrochloric acid react and give of 2 free Cl atoms

-Cl atoms break O3

Montreal Protocal

a global agreement to phase CFCs out of production to reduce ozone depletion

-CFCs → HCFCs (depletes O3 less, but is still a GHG)

-HCFCs → HFCs (still a GHG, but not ozone depleating)

-HFCs → HFOs

Solar radiation

not all incoming solar radiation will reach the earth’s surface

-about ¼ reflected back into space by clouds/atm.

-about 1/5 absorbed by clouds/atm

The rest reaches the earth’s surface and is reflected (higher albedo) or absorbed (lower albedo)

the greenhouse effect

gases in the Earth’s atmosphere trap heat from the sun and radiate it back down to earth

-solar radiation strikes the earth’s surface, heating it

-earth’s surface releases infrared radiation (HEAT)

-greenhouse gases absorb infrared radiation and radiate it into space and back towards earth

CO2 (GHG)

sources: FF combustion, deforestation, decomposititon

Methane (CH4)

sources: natural gas extraction, natural gas combustion, animal agriculture, anaerobic decomp.

Nitrous Oxide (N2O)

agricultural soils (denitrification of nitrate esp. in over watered/fertilized soils)

CFCs/HCFCs/HFCs

sources: regridgerants, blowing agents in aerosal products

water vapor

evaporation and transpiration from plants

*technically a GHG, but it doesn;t drive atmospheric temp change

Global Warming Potential

measure of how much a given molecule of gas can contribute to the warming of the atmosphere over a 100 yr period (relative to CO2) and depends on:

RESONANCE TIME: how long molecules stay in the atmosphere

INFRARED ABSORBTION:how well the gas absorbs and radiates infrared radiation

Thermal Expansion

-causes sea level to rise

-water molecules move farther apart when they’re heated (sea level rise)

-increased GHGs lead to a warmed climate and more melting of glaciers (sea lvl rise)

enviornmental impacts of sea lvl rise

-flooding of coastal ecosystems like (productive) estuaries (salt marshes, mangroves) no storm buffer

-low of species that depend on acrtic/tundra ecosystems like polar bears/penguins

-low of thaw-freeze cycle that glaciers go through, depriving surrounding ecosystems and human communities of water source

human impacts of sea lvl rise

-relocation of coastal human populations

-increase in flood frequency: higher insurance, repair costs, lost property

-saltwater intrusion (contaminating waters)

-refugees forced to move inland (becoming a refugee due to lost home and job)

Historic Climate Change

Earth’s climate has varied over geologic time, largely due to variations in Earth’s orbit around the sun

ECCENTRICITY: changes in eccentricity (orbit shape- 100,000 yr cycles) brings it closer/farther to the sun. More eccentric= farther from the sun

OBLIQUITY: (tilt 40,000 yrs)- exposing northern latitudes to higher insolation at different times

Milankovitch Cycles

predictable variation in earth’s climate based on eccentricity and obliquity

Earth’s Historic Climate

scientists have measured earth’s historic temp. and CO2 lvls based on 3 things:

FORAMINIFERA SHELLS in ocean sediment- different species have different temp. tolerances

AIR BUBBLES in ice cores that contain ancient CO2 levels

16O and 18O isotope concentrations in ancient ice

Ice ages

global ice ages occur, followed by warmer periods roughly every 100,000 yrs

CO2 levels v. temp

CO2 levels are strongly correlated w/ temp, but the CAUSALITY isn’t fully understood

effects of climate change

RISING TEMPERATURE: habitat/species loss, drought, soil desiccation, heat waves, inc. precipitation.

RISING SEA LEVEL: due to glaciers melting/thermal expansion

MELTING OF PERMAFROST: permanetly frozen tundra soils that begin to thaw and released mehane & CO2 from anaerobic decompositon

Impact of climate change coastal cities

property loss, damage from seawater, potential relocation(esp. poorer cities)

LOSS OF BARRIER ISLANDS: islands that buffer coastal communites/eco. from wind/rain

The Effects of CC on the Hadely Cell

WIDENING AND WEAKENING- as temp. differance between equator and poles decreases, air ascending and expanding from equator travels further before sinking

-shifts suptropical zones (dry desert biomes) towards to poles and expands the tropics

-regions between 300* and 60* may have a drier climate

effects of CC on the jetstream

WEAKENED, DESTABLIZED: as arctic warms faster than other areas of earth, temperature difference between equator and poles weaken

-because temp. and press. difference is what drives polar jet stream, less diff=weaker/wobbly

-leads to extreme cold spells in eastern US and dry spells in western US

Impact of CC on Marine Ecosystems

altered range of maine ecosystems: new marine habitats will be formed due to sea lvl rise flooding coast line. As oceans becomes deeper→ photic zones rise

altered ranges for organisms: warm water holds less O2, so many fish populations have declined or moved to colder waters

Impact of CC on Ocean Circulation

suppresion of thermohaline circulation: global ocean current that redistributes heat from the equator, salt, and nutrients by mixing ocean waters could slow or stop completely

-Ice melt from Greenland → freshwater buildup in North Altantic →Fresh water is less dense than salt → salt isn’t mixed

GLOBAL THERMOHALINE CIRCULATION SLOWS

polar amplification

polar regions of the earth are warming up faster than other regions causing unequal global warming

-especially in the arctic where there is more land and less water (less heat absorpsion)

-melting sea ice causes pos. feedback loop due to creating more water that absorbs heat

pollutants and unequal global warming

air pollution adds soot and other PM to atmosphere, distributed to poles by atmospheric circulation

-darker soot/PM covered ice absorbs even more hear due to lower albedo

Impact of CC on polafr ecosystems

Arctic sea ice loss= habitat loss → species loss

akgae that grows on ice (base of arctic foodweb) and polar bears

atmospheric warming ←→ocean warming

as the atmosphere warms, heat is transferred to the ocean

-the ocean absorbs hear radiated back to earth by GHGs (ocean absorbs much of earth’s heat)

-heat absorbed by ocean can be transferred back to the atmosphere for decades

effects of ocean warming on Marine species

warmer water holds less O2, causing respiratory stress or suffucation

-miratory routes, mating szns, reproductive timing can be disrupted

Habitat Loss: coral bleaching with heat inc.; shallow, sunny waters for coral melt as ice melts

Toxic algae bloom: toxic algae prefer warm H2O(release toxins that can kill, block sun, hypoxia)

coral bleaching

coral reef= mutualistic relationship between coral and photosynethic algae (zooxanthellae)

-algae has a narrow temp. tolerance and leaves the reef when the temp. rises(or from runoff)

-coral loses color and becomes stressed and vulnerable w/o main food source(algae sugar)

ocean acidification

INCREASED CO2 in atm. → INCREASED OCEAN CO2 (direct exchange)

-CO2 combines w/ ocean water to form carbonic acid

-carbonic acid dissociates into bicarbonate ion and H+ ion

Calcium carbonate and marine organisms

marine organisms that make shells use calcium and carbonate ions to build calcium carbonate shells (CALCIFICATION)

-CO2 increase (ocean acidification) makes carbonate ions less available

-marine shells breakdown as pH decreases and carbonate ions are less soluble in water

fewer carbonate ions=less calcification → weaker shells (coral/mollusks/urchins)

CC and ocean acidification

anthropogenic causes for ocean acid.=FF comb. (CO2), deforestation(CO2), coal/gas combustion (Nox, SOx → acid precipitation)

-CO2 increase directly correlated with ocean acidification

-inverse relationship b/w atm. CO2 and ocean pH (low pH = more acidic)