Oceanography Notes Midterm Corrections

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  • solar radiation received at the surface is retained for a time in the atmosphere; moderates temp day/night/seasons

  • 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 .6C in last 130yrs.

  • Possible effects:

    • -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: 1.4-5.8C 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

  • pump emissions into deep-ocean reservoirs

  • SOFAR channel: layer of ocean at 1000m caused by temperature and pressure conditions causing sounds from above and below to become bent in layer. Sound is trapped, transmitted long distances

  • Walter Munk: to use channel to detect global warming. ATOC exp

  • speed of sound in seawater increase as temp increase.

    Lecture Chapter 6 continued

      • Low pres; CCW rot

      • high pres ; CW rot

      • more evaporation over low pressure

      • most weather generated at seas

      • hurricane wind speed: at least 74mph

      • air exiting eye of hurricane comes out at left, but then once free, curves right

      • Coriolis affect ocean and atmosphere:

        • causes Hadley cells

        • causes W ocean basin current intensity [Gulf Stream]

        • causes CCW; tornadoes, hurricanes

      • “Fixed Reference Frame” -> “intertial frame”

      • gravity does not affect direction

    Wrong Answers from Site

      • Air rises at 60 degrees latitude and falls at 30 and 90.

      • Sun is directly over equator at both vernal and autumnal equinox

      • Water vapor contributes the most to greenhouse warming

      • Land breeze flows from land to sea

      • Wind belts created by lowermost portion of circulation cell

      • Surface winds of anticyclone in S hemis go CCW

      • most abundant gas in atmos is nitrogen

      • least abundant gas is carbon dioxide

      • polar easterlies between 60-90 degrees

      • polar front at about 60 degrees

      • increase earths tilt; warmer summers, cooler winters

      • Coriolis; CW rot around high, CCW rot around lows

      • air moves in and up in low pressure areas

      • surface winds in tropics [trade] blow W and toward equator

      • midlat storms: contrasting air masses, jet stream, westerlies, polar front

      • cause hurricanes: trade winds, warm ocean, water vapor rich warm air, jet stream

      • more intense storms maybe with global warming

    Chapter 7

      • ocean current: masses of ocean water from one place to another. Any mass, Any depth, simple or complex.

      • huge current system dominates surfaces, transfer heat from warmer to cooler areas.

      • transfer 1/3 of heat, wind belts transfer 2/3

      • sun drives surface currents

      • closely follow windbelt patterns

      • cold currents flowing toward equator on W sides of continents produce arid conditions

      • warm currents flowing poleward on E sides of continents produce warm, humid conditions

      • ocean currents contribute to mild climate of N Europe and Iceland; conditions at similar lats along Atlantic coast of N America much colder.

      • currents deliver ocygen in cold, dense water, and they helped prehistoric peoples travel

      • currents either wind or density driven

      • surface currents: caused by wind belts parallel to the surface. Horizontal

      • deep currents: caused by cold, dense water sinking. vertical

      • surface currents rarely flow in same direction at same rate

        • -measuring is difficult: can be measured directly or indirectly

        • -some consistency exists in overall surface current pattern

      • Direct measurement:

        • 1]floating device placed into current; tracked through time

        • 2]place device in current from fixed position

      • Indirect measurement:

        • 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

        • -mapped by:

          • -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.

      • subtropical gyres: 1]North Atlantic 2]South Atlantic 3]North Pacific 4]South Pacific 5]Indian Ocean [mostly S]

        • -coincide with subtropics at 30 N, S lats

        • -CCW in S hemis. CW in N hemis

      • Each composed of 4 mains currents that flow into one another:

        • equatorial currents: motion trade winds b/w tropics. From SE in S hemis, NE in N hemis.

          • -travel westward along equator: form equatorial boundary current of subtropical gyre.

        • western boundary currents: caused by coriolis effect deflecting the equatorial currents that have reached a continent away from the equator.

          • -Western boundary of subtrop gyres

        • Northern/Southern boundary currents: B/w 30 and 60 lat: caused by prevailing westerlies from NW in S hemis and SW in N hemis. Direct currents easterly.

          • -comprise Northern for N subtrop gyres, visa verse for S

        • eastern boundary currents: Coriolis effect and continental barriers turn currents toward equator when they flow back across the ocean basins

      • equatorial countercurrents: water on western margins flowing downhill under influence of gravity due to avg sea lvl at westward margins being as much as 2m higher than on eastern side.

        • -flow east

        • -apparent in pacific

        • -affected by shape of continents in Atlantic

        • -strongly influenced by monsoons in Indian ocean.

      • subpolar gyres: currents [of prevailing westerlies] moving westerly by polar easterlies

        • -at 60 lat

        • -rotate opposite the adjacent subtrop gyre

        • -smaller and fewer than subtrop gyres

      • 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: ~5lat 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

        • -high productivity

      • 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

    Antarctic divergence: around Antarctica where East wind drift scrapes 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 20F 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 18F 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

    -more upwelling

    -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

    -possitive numbers=Nino negative numbers=Nina zero=normal conds

    El Nino occurs avg every 2-10 years. Irregular pattern

    -lasts 12-18 months

    -some can last for years

    -more El Ninos in early 22nd century

    -most severe in 20th: 1982-1983

    Pacific Decadal Oscillation [PDO]: lasts 20-30 yrs. Influence Pac surface temps

    -pac in warm stage of PDO from 1977-1999, just having entered cool phase

    [Marine Galapagos Iguanas shrink]

    -mild nino affect only S pac ocean. severe affect world temp

    -difficult to predict

    -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

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