ATOC 182

pacific ocean

*most extensive and deepest* 40% of global ocean connected to arctic through narrow and shallow bering strait *largely open to the southern ocean* connected with indian ocean through indonesian sea known for a long time by peoples of asia and oceania - europeans found it 16th century *mariana trench 11,000 km deep* *high temperature in the W* *low temperature in the E (strong winds)* *lower salinity (more precipitation and rivers)* no formation of dense water (low salinity so more stratification) intense exchanges with the atmosphere at the equator circulation highlights: - equatorial counter current separates N and S - kuroshio brings warm water from gulf to california (not coast) - alaska and california ccurrents are cold along the coast N to S

which has a higher temperature: a tub or a candle?

candle

indian ocean

closed to the north by eurasia largely open to the southern ocean communicates with atlantic, equatorial pacific, and southern *highest surface temperatures* bay of bengal: low salinity (fresh water inflows from large rivers and precipitation) arabian sea: high salinity (strong evaporation) *strongest climatic seasonal variability* circulation highlights: - leeuwin current N to S brings warm water to east coast (unusual) - agulhas current connects indian to atlantic brings warm water W

important features of sea ice

complex surface that varies dramatically across even short distances - ridges, keels, cracks, snow 3 key features = leads, polynyas, and melt ponds

CTD probe

conductivity, temperature, depth - conductivity is a measure of how well a solution conducts electricity (salinity) - acquisition electronics placed in a pressure protected case connected to sensors

large thermal inertia of ocean

cools slower than land stores large amounts of heat during the day/summer and releases them at night/winter weakens the daily swings of temperature on earth

atlantic ocean

*second largest* narrow basin of great meridional extent - connects two polar basins and continental effects reinforced communicates with adjacent seas - nordic and mediterranean northern region is very studied because europeans trying to get to asia *saltiest* (influence of mediterranean and bridge with pacific) formation of dense waters in the north circulation highlights: - equatorial counter current separates N and S (NECC and SECC) - gulf stream transports warm water to N (up E N America down W europe) - reduces seasonal swings - brazil current transports warm water to S (down W S America up S Africa)

arctic ocean

*smallest and shallowest* enclosed by land connections with atlantic through nordic seas, baffin sea, and labrador sea connection with pacific through narrow and shallow bering strait early expeditions searching for NW/NE passages to north pole covered with sea ice in winter - *large seasonal variability* *lowest salinity* - low evaporation and a lot of river inflow low surface temperature and *higher underneath* - *salinity controls this stratification* circulation highlights: - transpolar current is dominant - beaufort gyre is a huge circular current driven by strong winds - north atlantic current transports warm saltier surface water from atlantic to arctic

distribution of water on earth

97% ocean ~2% ice caps (greenland, antarctica) and glaciers <1% rivers, lakes, wetlands, groundwater

vapor formation

1 meter of water evaporates each year from the surface ocean about 50% of solar energy entering the ocean results in evaporation this solar energy is later released during condensation, cloud formation, and rain

how can you measure ocean properties?

CTD probe, rosette, argo floats, gliders, and satellite observations

water mass

a body of water identifiable by its salinity and temperature or gas content sharing same history because it was formed in the same manner and place formed at the surface then sinks to depth depending on density - salty water either sinks because density of salt water is great or because fresh water moves in and pushes it down - gases can also be trapped in the interior ocean once received by the surface

distinguish temperature and heat

a colder body can hold more heat than a warmer body if it is larger (polar oceans) a body can be heated without changing its temperature

active sonar

a device that sends short pulses (pings) of high frequency sound and analyzes the returning echoes to gain information of geological, biological, or military importance - used for measuring ocean depth, geological investigations (sediment layers), archaeological studies, location of downed ships and airplanes

propagation of sound

a form of energy transmitted as a mechanical wave by rapid pressure changes in an elastic medium (gas, liquid, or solid)

salinity

a measure of the dissolved solids in seawater, usually expressed in g/kg or parts per thousand (‰) by weight seawater of salinity 35‰ means: 3.5% of that seawater consists of dissolved substances and boiling away 100 kg of that sea water would produce a residue weighing 3.5 kg

solvent

a substance capable of dissolving other polar molecules an ionic compounds - *water is a powerful solvent* - many biomolecules are either polar or charged so water readily dissolves these compounds

dissolution

action of water molecule *separating component elements* from a compound - salt - due to *polarity* of water molecule acting like a *magnet* at each positive or negative end

southern ocean

also called antarctic or austral ocean annular ocean encircling the antarctic continent connects 3 major oceans existence of antarctica was hypothesized by greek philosophers least known ocean because remote and inhospitable *strongest winds* antarctic treaty (1959) establishes region as scientific preserve surface temperatures show a zonal distribution surface salinity is heavily impacted by seasonal freezing of seawater and melting sea ice formation of dense waters along antarctic coasts circulation highlights: - antarctic circumpolar current is the *largest ocean current* flowing clockwise around antarctica - barrier to meridional exchange - cyclonic gyre circulates south of ACC - periantarctic current near the coasts (counterclockwise)

states

an expression of the internal form of a substance *change in state* is accompanied by an *input or output of energy* gas: fills container, high speed, low density, compressible liquid: free upper surface, flows freely, close molecules but slide past solid: strong, can fracture with stress, high density, molecules are locked

dynamics of sea ice in arctic vs antarctic

arctic: - sea ice is trapped in the beaufort gyre may circulate for several years - sea ice is trapped in the transpolar drift stream generally leaves in 1-2 years - trapping ice allows it time to thicken antarctic: - sea ice gradually moves to the northern ice edge after it forms - sea ice circulation is generally clockwise

lecture 4 key points

atmospheric circulation is key to ocean circulation composition and structure of atmosphere - atmosphere is composed of three main layers: troposphere, stratosphere, mesosphere - main gases are nitrogen and oxygen (air contains water vapor) - air density is influenced by temperature, water vapor content and pressure atmospheric movement - solar heating powers atmospheric circulation through differential heating between latitudes - coriolis force deflects the path of an object that moves within a rotating frame large scale atmospheric circulation - there are three main atmospheric circulation cells (hadley cell, ferrel cell, and polar cell) - intertropical convergence zone, subtropical highs, trade winds, westerlies, polar easterlies storms - weather is different than climate - atmospheric disturbances - extratropical cyclones form between two air masses - tropical cyclones form in one air mass

argo floats

autonomous profiling floats drifting with currents to measure temperature, salinity, and pressure - can also be equipped with sensors measuring other variables - between surface and 2 km - sends profiles by satellite once at the surface

seasonal cycle of sea ice

autumn: ocean begins to freeze and sea ice begins to grow winter: sea ice continues to grow and become thicker spring: sea ice begins to melt summer: sea ice completely melts unless it has grown thick enough to not

what is the residence time of water in the ocean vs atmosphere?

ocean = 4100 years atmosphere = 9 days thousands of cubic km transferred each year

refraction

bending of light or sound waves as they move at an angle other than 90˚ between media of different optical or acoustical densities - 90˚ is when it's reflected - due to the wave not traveling at the same speed in different media or same media of unequal densities

brine rejection

brine: droplets of highly saline water - formed due to salt accumulation in small pockets as ice crystals form brine rejection: process of brine being expelled back into the ocean - raises the salinity of the near surface water, so increases its density (dense water formation) - over time brine drains out so sea ice salinity decreases - salty sea ice = young, fresher sea ice = old

classification of sea ice

by stages of development that *relate thickness to age* new ice: < 10cm thick young ice: 10-30cm thick first year ice: > 30cm thick but has not survived a summer melt season multiyear ice: 2-4m thick and has survived a summer melt season

sea ice

covers 15% of the ocean at some point in the year ice absorbs incoming energy from the sun during the summer/day - ice melts (latent heat of fusion) ice releases energy back to the atmosphere during the winter/night - ice freezes (latent heat of fusion) heat content of water changes but temperature doesn't ice *contributes to moderate abrupt temperature changes*

as temperature increases, density _____

decreases

sound intensity ______ as it travels through the ocean because...

decreases... as it travels it spreads, scatters, and gets absorbed - spreading: sound moves away from the source - scattering: sounds bounces off bubbles, particles, organisms - absorption: energy being converted into heat

lecture 6 key points

density induced water movement - due to temperature and salinity variations, the ocean displays regional density variations - density variations produce horizontal pressure gradients that generate large scale oceanic movement - thermohaline circulation is responsible for the circulation of the global ocean as a whole formation of water masses - form through processes occurring at the ocean surface (heating/cooling) - mode waters correspond to thick layers of weak vertical stratification (part of central waters) - intermediate waters are characterized by a vertical salinity extremum at intermediate depth - deep waters originate most often from a mixture of several water masses - bottom water form through freezing of seawater or strong evaporation (densest waters) the great conveyor belt - the great conveyer belt is the general circuit water masses use - regions of dense water formation, upwelling forced by winds or through mixing - some ascending and sinking and exchanging studying currents - current meters measure the speed and direction of currents - acoustic doppler current profiler - a variety of floats have been used to follow circulation (drifting buoys)

lecture 7 key points

el nino/la nina - el nino = southern oscillation (ENSO) is a climatic anomaly due to changes in atmospheric pressure - el nino phases are associated with warm episodes in the east pacific (weak/reverse trade winds) - la nina phases are associated with cold episodes in the east pacific (strong trade winds) - climate indices are used to characterize ENSO phases (oceanic nino index) monsoons - the ITCZ changes location with season due to differential heating by the sun between hemispheres - monsoons are patterns of wind circulation that change with the season - rainfall associated with monsoons are important for drinking water and agriculture in many places polynyas - polynyas are irregularly shaped areas of persistent open water - coastal (latent heat) polynyas are mainly due to the action of wind blowing sea ice away from the coast - open ocean (sensible heat) polynyas are due to the upwelling of relatively warm waters - impact ocean circulation, regional and global climate, and wildlife oceanic eddies - swirling fluid associated with a turbulent flow regime (weather of the ocean) - ubiquitous features of the ocean that are most present in strong currents - play a key role in ocean circulation and transport of physical and biological tracers

heat

energy produced by the random vibration of atoms or molecules *action* - how much energy (Joules)

ice formation

freezing point: the temperature at which a solid can begin to form as a liquid is cooled - pure water: 0˚C - seawater: -2˚C (why we put ice on side walk) heat removal is required to change liquid water to ice forms crystal lattice - takes up 9% more space than liquid water - ice is less dense and that's why it floats

freezing of seawater

fresh water freezes at 0˚C but seawater freezes at a lower temperature depending on salinity in polar regions salinity is around 35 ppt so water begins to freeze at -1.8˚C

dissolution of gases

gases from the atmosphere dissolve in seawater at the *ocean's surface* found in different proportions in the atmosphere and ocean because of different solubility in seawater *increases with colder temperature*

how would a red fish appear at a few meters from the surface?

grey - red is absorbed within the first couple meters

latent heat of vaporization

heat added to a liquid during evaporation (or released from a gas during condensation) that produces a change in state but not a change in temperature

sensible heat

heat exchanged *accompanied by a change in temperature* detectible by a thermometer

latent heat

heat exchanged *without a change in temperature* chang in state

latent heat of fusion

heat removed from a liquid during freezing (or added to a solid during thawing) that produces a change in state but not in temperature

sound speeds up as temperature and pressure ______

increase - competitive effect of temperature and pressure - minimum sound velocity found at 1000m

positive feedback of ice albedo

increased temperature from incoming solar energy sea ice melts darker surfaces revealed albedo reduced increased absorption of solar radiation increased temperature

as salinity or pressure increase, density _____

increases

polynyas

irregularly shaped areas of persistent open water (holes)

does water have a small or large heat capacity?

large (1 cal/g/°C) water can absorb/release large amounts of heat while changing little in temperature

SOFAR layer

layer of minimum sound velocity in which sound transmission is unusually efficient for long distances - sounds leaving this depth tend to be refracted back into it - loud noises can be heard for thousands of kilometers

propagation of light in the ocean

light is reflected by clouds and sea surface light is scattered/absorbed by atmospheric gases and particles water rapidly absorbs all EM radiation the top meters of the ocean absorb nearly all the wavelengths the energy of some colors is absorbed nearer to the surface violet, green, and blu travel deeper into water

leads

long linear areas of open water ranging from a few meters to > km wide and 10s of kms long - develop as ice diverges

heat capacity

measure of the heat required to raise the temperature of 1 g by 1 °C different substances have different capacities

rosette

metal frame holding water sampling bottles - CTD often attached to a rosette - niskin bottles open at both ends, closed by a messenger at a depth to trap water

three density zones

mixed layer: upper layer, temperature and salinity are constant with depth - well mixed by wind - lots of wind and cold = big mixed layer pycnocline: middle zone, density increases rapidly with depth deep zone: bottom zone, little change of density with depth, 80% of world's water

dissolution of gases in the ocean

nitrogen (N): 48% - used by organisms to build proteins oxygen (O): 36% - used by animals to respire and plants to photosynthesize carbon (C): 15% - used by plants

lecture 5 key points

ocean currents are produced by two factors - winds produce surface currents and density differences produce thermohaline currents direct wind forcing - ekman spiral was discovered following observations taken during the Fram expedition - ekman transport is the resultant net flow of water over the ekman spiral - movement of water associated with ekman transport cause upwelling and downwelling resultant geostrophic currents - geostrophic currents result from a balance between the pressure gradient force and coriolis force - geostrophic gyres are circuit of midlatitude currents around the periphery of ocean basins - increase of the coriolis effect with latitude causes the westward intensification main geostrophic gyres and currents - there are six great surface circuits: 5 geostrophic gyres and the antarctic circumpolar current - western intensification cause major differences between W and E boundary currents - wind stress on the ocean in the tropics and midlatitudes give rise to transverse currents - surface currents distribute tropical heat worldwide thus influencing weather and climate

what are the 5 oceans?

pacific, atlantic, indian, southern, arctic there is one world ocean but it's divided into regions - boundaries have evolved over time

different zones in the ocean (light)

photic zone: the thin film of lighted water at the top of the ocean - usually around 50-100m but can reach 600m - most of the ocean's life is found here aphotic zone: the dark ocean below the depth that light can penetrate only 10s of meters at the top of the photic zone receives enough light to have photosynthesizing species

why is the O2 concentration high at the surface and CO2 concentration low at the surface?

photosynthesizing organisms are at the surface - use CO2 and produce O2 (photosynthetic process)

melt ponds

pools of melted snow and ice on the sea ice surface created during the summer melt - appear during the summer as the snow on top of sea ice melts and results in meltwater accumulation

cryosphere

portions of earth's surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps, ice sheets, and frozen ground

thermodynamics

processes that affect the growth and melt of sea ice ice growth slows as the ice thickens - to freeze, water needs to release heat, harder to do with more ice above it sea ice melts from the top due to solar energy and from the bottom and side due to warm water albedo: non-dimensional quantity indicating how well a surface reflects solar energy - 0 = perfect absorber - 1 = perfect reflector - sea ice = 0.5-0.7 - ocean = 0.06 (6% reflected back)

principle of constant proportions

proportions of major salts in seawater remain nearly constant *regardless of salinity* amounts of dissolved salts per unit volume of ocean are nearly constant - ions are added to the ocean at the same rate they are removed - ions are removed from the ocean through precipitation into solid compounds that sink to the seabed

interactions between sea ice sheets

rafting: currents or winds push around thin ice so they slide over each other ridging: sea ice is pushed around into piles that rise and form small mountains above the level sea ice surface

propagation of light

reflection: the change in direction of light at an interface between two different media so that light returns into the medium from which it originated scattering: the dispersion of light waves when they strike particles suspended in water or air absorption: conversion of light energy into heat

satellite observations

remote sensing from aircraft or satellite surface temperature given by infrared sensors salinity given by sea surface microwave emission advantage = broad spatial and high temporal coverage disadvantage = only give surface information

gliders

robotic autonomous underwater vehicles which are telecommanded - use wings and archimede's principle to achieve buoyancy-based propulsion - achieve vertical and horizontal motions within the top 1500m for up to several months - equipped with a gps that gives their position when they are on the surface - can measure temperature, salinity, oxygen, chlorophyll animal born instruments - animals equipped with conductivity temperature depth sensors (not harmful) - animals collect profiles on dives and transmit information when rising to surface to get air

pancake ice pathway

rough bottomed rough ocean frazil ice - pancake ice - rafting/ridging - cementing/consolidation - sheet ice

what does density depend on?

salinity, temperature, and pressure

dynamics of sea ice

sea ice is almost continually in motion (except for fast ice) fast ice: immobile sea ice, anchored to the shore or ocean bottom (fastened) principle forces: - wind: primary force responsible for ice motion, induces a drift of sea ice - ocean currents: act as a drag to the wind driven ice motion - coriolis force: deflects ice motion to the right in the N and left in the S - internal ice stress: resistance to the wind driven motion and is responsible for sea ice deformation (compactness/strength) - sea surface tilt: influences the motion of sea ice

evaporation

type of vaporization (liquid to gas) *without reaching boiling temperature* heat energy added to water allows *hydrogen bonds to break* - individual water molecules diffuse in the air evaporation cools a moist surface (departing molecules of water vapor carry the energy away *more energy is needed to change liquid water into vapor than into ice* - needs that extra energy to break hydrogen bonds

does sound travel better in air or in water?

water - speed in air: 300 m/s - speed in water: 1500 m/s

lecture 3 key points

sea ice is part of the cryosphere - cryosphere encompasses all the regions of the world where water is frozen sea ice characteristics - in polar regions water freezes at -1.8˚C (brine rejection) - frazil, pancakes, rafting, ridging (classified by stage in development) - complex heterogeneous surface (leads, polynyas, melt ponds) processes, interactions and role in the climate - ice-albedo feedback - main forces = wind and currents - interacts with atmosphere, oceans, ice caps, glaciers, and biosphere - plays an important role in the climate system (not on sea level) studying - in situ observations provide a large variety of information on sea ice but sparse - satellite observations provide continuous records (sea ice concentration and extent) arctic vs antarctic sea ice - oppose in many aspects (land configuration and history) - arctic has thicker and older sea ice less snow and a more asymmetric pattern - arctic sea ice has been strongly declining

temperature and salinity profiles by time

seasonal warming creates a warm layer which remains at the surface - too much energy would be needed to mix seasonal thermocline forms in temperate regions

frazil

small needle like ice crystal, typically 3-4 mm in diameter, suspended in water two processes of growth depending on climatic conditions - calm ocean: frazil crystals develop into smooth sheets of sea ice - rough ocean: frazil crystals accumulate into slushy circular disks called pancakes

grease ice pathway

smooth bottomed calm ocean frazil ice - grease ice - nilas - rafting - congelation ice - sheet ice

does sound or light travel better in water?

sound - marine animals use sound rather than light to get information

sonar

sound navigation and ranging

thermal inertia

tendency of a substance to *resist change in temperature* with the gain/loss of heat

what controls temperature of surface waters?

the amount of incoming solar radiation - more at the equator and tropics than the poles

what controls salinity of surface waters?

the exchange of water between the atmosphere and the ocean

density

the mass per unit volume of a substance (kg/m^3) seawater (1020 to 1030 kg/m^3) has a greater density than pure water (1000 kg/m^3) - because of the weight of the solids (salts)

salinity variation

the ocean's salinity varies from 33‰ to 37‰ evaporation, precipitation, and freshwater runoff from continents influence salinity *mediterranean* is so *salty* because *high evaporation* rates *arctic* is so *fresh* because *many rivers* and *low evaporation* rates *NE of S America* is so *fresh* because *amazon river*

why does the ocean appear blue?

the only wavelength that can travel deep into the ocean before being absorbed - has more time to scatter and then reflect

temperature

the response of an object to the input or removal of heat energy *response* - how cold or warm (°C)

lecture 2 key points

there are 5 oceans: atlantic, pacific, indian, arctic, and southern density stratification - density depends on temperature, salinity, and pressure - equation of state - three density zones: mixed layer, pycnocline, deep zone - thermohaline, halocline water masses - body of water sharing similar properties and history - TS diagrams are used to study water masses distinctive features of five oceans - atlantic: narrow ocean, saltiest, formation of dense water - arctic: small, shallow, enclosed, strong seasonal variations - pacific: wildest, deepest, no formation of dense water - indian: highest temperatures, strong seasonal variations - southern: large, annular, connected to major oceans, dense water formation measuring ocean properties - CTD rosette, autonomous float (argo and gliders), animal-borne - remote sensing, satellite observations

importance of leads, polynyas, and melt ponds

they absorb more solar energy than the surrounding ocean, leading to melting of surrounding ice also leads and polynyas are important for wildlife to breath and to fish

temperature and salinity profiles by region

tropical: strong thermocline and halocline, strong stratification temperate: weak to strong thermocline (seasons), moderate stratification polar: almost absent thermocline and moderate halocline, weak stratification

which has more heat: a tub or a candle?

tub

echo sounder

type of sonar used to determine the depth of water by transmitting sound pulses into water

pH

water can separate to form H+ and OH- acid: substance that releases a hydrogen ion in solution base: substance that combines with a hydrogen ion in solution scale: indicates acidity and basicity (alkalinity) by measuring concentration of H+ in a solution - basic > 7.0 - acidic < 7.0 - neutral = 7.0 - a change of 1.0 pH represents 10x change in H+ ion concentration in the ocean: - seawater is slightly alkaline (basic) with an *average pH of 7.8*

what does high latent heat of vaporization mean?

water vapor transports more heat than liquid water (per unit of mass) - *2/3 of heat transport between the equator and the polar region are effected through moving air masses* (that contain water vapor) - the other 1/3 is due to ocean current transportation

constituents of salinity

weathering of surface rocks and input from deep crustal and upper mantle sources through volcanism major ions: Na+ and Cl- (sodium and chloride) trace element: minor constituent present in amounts <1‰

why are west coast cities in the US more moderate for temperature?

westerlies come from pacific and bring cool air that stabilizes the temperature

pycnocline

zone of ocean in which density increases rapidly with depth

halocline

zone of ocean in which salinity increases rapidly with depth

thermocline

zone of ocean in which temperature decreases rapidly with depth

lecture 1 key points

~97% of water on earth is in the ocean water molecule: - formed of 2 hydrogen atoms and one oxygen atom - polarity of molecule allows for dissolution, adhesion, cohesion physical and chemical properties of seawater: - large heat capacity helps regulate climate - powerful solvent (of salts and gases) - density decreases as temperature increases - density increases as pressure and salinity increase physical states: - gas (water vapor), liquid, solid (ice) - latent heat (state change) vs sensible heat (temp change) - ice is less dense than water and latent heat of fusion - evaporation and latent heat of vaporization propagation of light and sound: - light is rapidly absorbed in water (reflection, scattering, absorption) - sound propagates further than light (used to measure depth)