water vapor contributes more to greenhouse effect more than any other gas.
unaffected by human activity
CO2 concentration increase 30% over 200years
-increase by 1.2ppm/yr
the other greenhouse gases, though lesser concentrations, are important, because they absorb far more infrared radiation per molecule than CO2. But still, not as important as CO2.
Melting glaciers, early springs, species distribution shift, rise in average temp all indications
Avg temp up .6C in last 130yrs.
-higher sea-surface temp [more tropical storms, alteration in deep water currents]
-most severe drought, more intense precip
-water contamination [larger outbreaks disesase]
-longer/more intense heat waves
-shift in distribution of life
-melting ice caps [rising sea lvl]
possible that ice caps enlarge. how?: Warmer temp->more evp->more precip on land->potentially increasing snowfall for creation of ice caps->lower sea lvl
some positives: increased growing season some places, plant like flourish w/ CO2
CO2 estimates prior to 1958 estimated from air bubbles in ice cores
Intergov’l Panel on clamate change [IPCC] 1988; 200 scientists begin studying human effects on global warming; conclude that human impact exists.
sedimentary rock and forests are natural storage places for organic CO2; being released.
Kyoto Protocol: 1997; 60 nations; voluntary reduce emissions. US to reduce emissions 7% below 1992 emissions by 2007: WE FUCKING WITHDREW! Also to transfer technology to other countries with them becoming producers of much greenhouse gas
2nd IPCC: 2001: 1.4-5.8C temp increase between 1990-2100
Oceans absorb lots of CO2
CO2 30x more soluble in water than other gases
more CO2 found in ocean than in atmosphere
most of this CO2 incorporated into organisms ->photosynthesis
ocean acts as sink for CO2; soaks it up, deposits it as sea floor deposits.
by removing more CO2 from ocean, it can absorb more
iron hypothesis: John Martin 1987; productivity low in tropical regions because absence of iron, he proposed fertilizing ocean with iron.
adding iron to ocean increase productivity up to 30x
long term effects adding iron and CO2 to ocean are unknown
fear of oxygen depletion in these areas. some companies filed patents
-some consistency exists in overall surface current pattern
1]floating device placed into current; tracked through time
2]place device in current from fixed position
1]determine the internal distribution of density and the corresponding pressure gradient across an area of the ocean
2] radar altimeters [TOPEX/Poseidon satellite 1992]: determine bulge’s in sea surface which are results of the shape of the underlying sea floor and current flow. dynamic topographic maps produced from this data that show speed/direction of surface currents
3]Doppler flow meter to transmit low-frequency sound signals through the water. measures shift in frequency between the sounds water emitted and those backscattered by particles in the watter to determine current movement.
deep current measurement:
-more difficult to measure because of depth
-device carried with current
-tracking telltale chemical tracers
-some traces absorb into seawater, other intentionally added
-useful tracers [tritium from atom bomb tests][chlorofluorocarbons freons and other gases]
-measure temp/salin characteristics of deep ocean currents
surface currents occur within/above pycnocline to a depth of 1km
surface currents only affect 10% of ocean water
due to friction with wind
2% of winds energy transferred to ocean surface. 50-knot wind produces a 1-knot current
if not continents, surface currents would follow major wind belts.
-interaction between trade winds and prevailing westerlies creates circularmoving loops of water in Atlantic ocean
gyre: large, circular-moving loops of water driven by major windbelts.
Fridtjof Nansen: 1861-1930; Norwegian explorer; voyage in unexplored Arctic
Fram: his ship. 39m. wooden; designed to be pushed to surface by freezing water
nansen bottle: for collecting water samples at depth
Arctic ocean ice moves 20-40 to the right of wind blowing across its surface
-in S hemis, surface currents move to the left of wind direction
V. Walfrid Ekman: [1874-1954]; Swedish physicist; developed:
Ekman Sprial: explains Nansen’s observations in accordance with Coriolis effectl describes speed/direction of flow of surface waters at various depths
-assumes a uniform column of water set in motion by wind blowing across surface
-N hemis: immediate surface water flow 45 to right of wind [S hemis left]
-as surface water moves, it sets in motion other “layers” beneath it
current speed decreases with incrasing depth, and coriolis effect increase curvature to right
at same depth, water may move exactly opposite the direction the wind that started it is going.
deep enough water, friction consumes energy of wind and there’s no motion: normally occurs at 100meters.
Ekman Transport: All layers combine to create new water movement that is 90 from the direction of the wind. 90 right of wind in N hemis, left in S hemis
-nothing is ideal: Ekman Transport in open ocean is typically 70, nearly same direction as wind in shallow coastal waters
subtropical convergence: water in middle of a gyre, causing water to literally pile up in center of subtrop gyre. caused by Ekman transport causing CW rotation within ocean basin
-resulting in all subtrop gyres having a 2meter high hill
geostrophic current: when coriolis effect and gravity balance, causing the water wanting to fall down the hill to move around it.
-path of the ideal geostrophic flow
-hill has a steeper westward slope
-path of actual geostrophic flow: friction results in this current eventually downhill
El nino event affects currents greatly
S Pacific less intense than other gyres, because large area, many islands.
there is a narrow and strong flow to north on western side of subtrop gyres in N hemis.
narrow strong flow to South in S hemis [still on W boundary of gyre]
general: western boundaries of subtrop gyres faster, narrower, deeper
-due to apex being closer to W side
-Kuroshio 15x faster, 20x narrower, 5x as deep as Cali current
western intensificiation: this phenomenon: currents affected by this are western intensified
-ALL W boundaries of subtrop gyres are western intensified
-Coriolis effects eastward, high lat water, making it turn toward equator more strongly;
-causes wide, slow, shallow flow of water toward equator across subtrop gyres [picture a funnel]
-surface currents directly influence climate of adjoining landmasses
-warm current; warm air; rain over continent
-continental margins with warm offshore currents typically have humid climate [E coast]
-temperature migrate N-S with seasons
-continental margins with cold offshore currents typically have drier climate [W coast]
Upwelling: vertical movement of cold, deep, nutrient-rich water to surface
Downwelling: surface water -> deeper
productivity: presence of microscopic algae
-cold water= better productivity supports larger marine life
downwelling less productivity, but carries oxygen dissolved to deep-ocean life
current divergence: surface water away from an area on ocean’s surface: equator
geographical equator: 0 lat
meteorlogical equator: ~5lat N
equatorial upwelling: caused by trade winds causing current divergence -> Ekman transport causes surface water N of equator to veer right [Northward] and water south of equator to veer left [southward]: divergence of surface current along geographical equator
current convergence caused by currents movement toward each other
ex] N Atlantic; Gulf Stream, Labrado, E Greenland currents come together
water piles, sinks
coastal winds can cause either welling due to Ekman transport
coastal upwelling: caused by coastal wind from the S [in S hemis] causing Ekman transport to move coastal water to the left, away from coast [on a western coast of continent] Water from below rises to replace this water
-W coast US experience this. Natural air conditioner in the summer
coastal downwelling: just the opposite.
both upwelling and downwelling common in high latitudes
absence of pycnocline allows lots of vertical mixing
upwelling also caused by: offshore winds, seafloor obstructions, sharp bend in coast.
Chapter 7 Lecture
Most productivity in coastal areas
summer in Arabian sea, wind blows SW->NW with respect to India
eastern boundary currents greatly affected by coriolis effect
ice dam cold water into oceans would hinder N Atlantic circulation
Chapter 7 cont…
Antarctic circulation dominated by movement of water mass South of 50 S lat
anarctic Circumpolar Current [West Wind Drift]: main Antarctic current; encircle antarctica W->E at 50 S lat, but varies b/w 40 and 65 S lat directed from Antarctica
subtropical convergence: 40 S lat; N boundary of ACC
ACC powered by prevailing westerly wind belt “Roaring Forties, Furious Fifties, Screaming Sixties”
Antarctic Convergence [Antarctic Polar Front]: 50 S lat: cold dense Antarctic meets and sinks below warm less-dense sub-antarctic waters. Marks N boundary of southern/Antarctic ocean
East Wind Drift: surface current propelled by polar easterlies. E->W
-most developed in Wedell and Ross seas.
-directed toward Antarctica. closer to cont than ACC
-much marine life during S hemis summer b.c of upwelling created here
Gulf Stream: N along US coast. Best studied of all ocean currents. W-boundary current. 31-47m wide. Fastest in world. W boundary of gulf stream is abrupt. E boundary not so much.
Sargossa Sea: the water that circulates round rotation center of N atlantic gyre. “stagnant eddy”
transport off Chespeak bay 100 sverdrups [ more than 100x great than combined flow of all world rivers]: water from Sargossa sea combining with Florida current
-this water from Sargossa sea returns at Newfoundland.
meanders: snaked-like bends in current which often disconnect from gulf Stream and form large rotating masses of water called vortexes, eddies, or rings.
-mechanisms that produce the dramatic water loss as Gulf S moves N yet to be determined
warmcore rings: warm Sargossa sea water surrounded by cooler water. Shallow bowl-shaped, 1k deep. 68m wide. These spin off the Gulf Stream to the North, rotating CW
coldcore rings: cold nearshore ring. cone-shaped. 2.2m deep. 310+ miles wide, increasing with depth, sometimes reaching sea floor. These spin off of Gulf Stream to the South, CCW. move SW 2-4m/day; often rejoin GS at Cape Hateras. Impact sea floor sed.
-both rings: unique temp chars, biological pops; warm-water organism in cold ocean and visa versa; can survive as long as ring does, 2yrs sometimes.Coldcore rings last longer, and have more life.
Ben Franklin postmaster discovered Gulf Stream.
Labrador current: with the gulf stream form much fog in N atl, then break into Irminger current along Iceland’s W coast and Norweigan current moving N on Norway’s coast
North Atlantic Current: crosses N atlantic. turns south to become canary current.
Gulf Stream moderates E coast temp and N Europe temp, so temps across atlantic in Europe much higher even though on same lat, b/c of heat transfer from GS to Europe. Spain, Portugal at same lat as NE states.
-as much as 20F warmer
-the difference b/w S and N temp on E coast much greater than b/w N and S coasts of Europe.
equatorial counter current of pacific better developed in pacific
Walker Circulation Cell: in equatorial S pac: caused by pressure difference between W and E pacific. SE trade winds blow across pacific.
-1920 effect first describe; Sir Gilbert Walker.
Normal conditions: walker cell rotates CW. Low pressure in the West, high pressure in the E
pacific warm pool: warm water flowing in equatorial regions creating a wedge of warm water on the western pacific. Thermocline below 100m
-thermocline in E is generally within 30m of surface
El Nino: current equatorial around Christmas: intense rainfall. CC air rotation
southern oscillation: name given to phenomenon of E-W pressure seesaw accompanying the warm current.
El Nino South Oscillation [ENSO]
El Nino; low pressure along equatorial regions in S America. SE trade winds diminish, sometimes reverse. CCW air rotation
-warm pool flows back from west
-begins to move in sept: at S American in dec/jan
-water off S American coast up to 18F warmer than normal
-sea lvl increase as much as 8in [thermal expansion along coast]
-increases number of tropical storms
-thermocline flattens; more horizontal
-downwelling sometimes occurs
-productivity diminishes, life reduced
-high pressure replace Indonesian low; dry conditions
-La nina [cool phase]
-closer to normal conditions
-stronger walker cell instead of reverse one
-stronger trade winds
-shallower thermocline in e pac
-band of cooler than norm water stretch across equatorial S pac
-commonly occur right after Nino
ENSO Index: show alternating conditions since 1950 between Nina, Nino.
-Calculated by atmospheric pressure, winds, sea surface temp
-can result in: flooding, erosion, droughts, fires, tropical storms, and effect marine life.
La Nina sea surface temp and weather opposite of Nino
El Nino events do occur in ocean basins
Tropical Ocean-Global Atmosphere [TOGA]: 1985 study how El Nino event develop. predict el nino 1 yr
Tropical Atmosphere and Ocean [TAO]: After TOGA: continues to monitor. 70 moored buoys.
Indian counter current flow between 2 and 8 S of equator instead of N b/c Indian ocean is mostly in S hemis.
monsoon: N Indian ocean wind pattern
northeast monsoon; atmospheric masses off Asian continent into Indian ocean. From NE->SW during winter
because of low heat capacity of land, continent heats faster than ocean in summer, creating low pressure area, resulting in the winds reversing: southwest monsoon: thought of as continuation of SE trade winds across equator.
North equatorial current gone during summer, replaced by southwest monsoon current W to E
Agulhas current: S along African coast, joins ACC
Aghulas Retroflection: abrupt turn as current collide [ACC]
deep ocean current affect 90% of ocean water. moves more water slower 6-12 miles per year.
take 1 year for 1 hr travel of surface current for deep current
thermohaline circulation: deep ocean circulation because differences in temperature and salinity cause dense differences