MSCI Exam 2
More Ways Salt is Removed
4. Organisms tend to concentrate salts • Lost if harvested • Also in shells and exoskeletons 5. Adsorption = ions and molecules sticking to a particle's surface • Can remove ions; clays do it a lot, fecal pellets, skeletons • Most significant removal process 6. Cycling through crust at ridges (adds and removes salts) • Cycles volume of all oceans every 10MY
Atlantic Ocean Water Masses Cont.
3. Antarctic Bottom Water (AABW) • Densest water in the oceans • Edge of Antarctica, formed by sea ice • Flows slowly north but can't cross midAtlantic ridge (not thick enough) • → stays on west side until equator 4. South Atlantic Surface Water • @60S Divergence zone, moves north 5. Mediterranean Intermediate Water • High salinity, sinks to 1000m
Structure of the Atmosphere Continued
3. Mesosphere • Temperature decreases with height • Little absorption, so temperature decrease • Pressure is 1/1000th of surface 4. Thermosphere • Extends out to space • We will focus mostly on the troposphere
Where are the Horse Latitudes located?
30 degrees N/S
Why are CFC's bad for the ozone layer?
They react with UV radiation, releasing chlorine. The chlorine destroys ozone.
Reversal of prevailing winds
-summer high pressure off coast produces northerly winds -winter low pressure off the coast produces southerly winds
Units of Concentration
1. By Weight: • g/kg (ppt); mg/kg (ppm); µg/kg (ppb) 2. By Volume: • g/L; mg/L; µg/L • 1L~1kg so these are pretty close to #1 3. By Molarity: • 1 mole = substance's average molecular weight • Ex: H2O: 2H + 1O = 2 (1g) + 1(16g) = 18g
Causes of Western Intensification
1. Eastward turning of Earth 2. Increase of Coriolis Effect with latitude 3. Prevailing winds' speed and direction changing (trades vs. westerlies) 4. Friction between land masses and ocean currents • Overall water transport is about the same, but different speeds
Atlantic Ocean Water Masses
1. North Atlantic Deep Water (NADW) • At boundaries of Gulf Stream, Labrador, and Greenland Currents 2. Antarctic Intermediate Water (AAIW) • Upper boundary of NADW
General Water Layers of the Oceans
1. Surface 0-200m 2. Intermediate 200-2000m 3. Deep 2000-4000m 4. Bottom >4000m
Marine Oxygen
Adding Oxygen: • Photosynthesis - plants, cyanobacteria, some protists • Use CO2 and light to make sugars and O2 • Must occur in euphotic zone - where light penetrates (up to 200m) • Air-sea interactions - waves, wind, diffusion, etc. Removing Oxygen: • Respiration - all living things do it. Even plants/algae.
Which of the following is not an instrument for measuring salinity?
Anemometer
Major Ocean Currents: Antarctic
Antarctic Circumpolar Current, AKA West Wind Drift • Only one that flows around globe without interruption • Important for mixing waters from all the oceans • Biggest surface current on earth
As you increase in altitude, temperature __ in the Troposphere and __ in the Stratosphere.
Decreases; increases
Carbonate acts as a buffer in the oceans. This means __.
It prevents large or fast changes in pH.
Where would you expect to find the highest salinity?
Landlocked seas
Why do CO2 levels in the atmosphere increase in the fall and winter and decrease in the spring and summer?
Less photosynthesis and more decay in the winter months
The title of having the strongest sustained winds of any modern hurricane and the most intense storm (in terms of pressure) in the western hemisphere belongs to hurricane __.
Patricia
When too much freshwater is pulled from an aquifer and seawater begins to infiltrate it, it is known as __.
Saltwater intrusion
Indian Ocean Water Masses
Small amounts of AABW/Circumpolar water and AAIW • Some warm salty water at surface in subtropics
What piece of global legislation greatly helped reduce the production of CFC's?
The Montreal Protocol
Where are the Doldrums located?
The equator
Why are the most abundant ions in rivers the least abundant ions in the oceans?
The ones that are most easily dissolved will already have been transported to the oceans
Which of the following does not remove salts from the oceans (at least temporarily)?
Volcanic eruptions
Let's say you are on a date with someone you really like and you want to impress him/her with your vocabulary prowess. You want to demonstrate the meaning of adsorption while eating dinner at a nice restaurant. Which of the following would accomplish this?
You smear your chicken alfredo all over your body, claiming "I am the master of adsorption!". Your date leaves. But at least you knew the true meaning of adsorption which is better than nothing.
What are the two main methods of geoengineering (climate engineering)?
carbon dioxide removal and solar radiation management
The crust contributes mostly __ to the oceans, from cooling magma.
cations
What effect does increasing salinity and increasing temperature have on the dissolved oxygen equilibrium concentration in seawater, respectively?
decreases; decreases
If the earth stood still and was completely covered with water, the northern hemisphere surface would experience __ winds and the atmosphere would experience __ winds.
north; south
The amount of solar energy that would hit the surface at a right angle without an atmosphere is called the __.
solar constant
Open Ocean Permanent Downwelling Zones
• 5 Convergence Zones: • Tropical convergence - at equator • Subtropical 30-40N&S • Arctic & Antarctic 50N&S • #2&3 are centers of ocean gyres • Downwelling→ low nutrients, low productivity
Water Usage in the U.S.
• 70% FW in U.S. goes to agriculture • 22% to industry • 8% domestic
The CO2 Cycle
• Currently, oceans absorb 1.6-3 billion metric tons of CO2 per year • Rate depends on: • Temperature • pH • Salinity • Biological activity • Mixing
Rain Bands
• 0 and 60oN/S: low pressure zones - lots of clouds and rain • 30 and 90oN/S: high pressure - dry, clear skies • → affects surface salinities • Tropics - lots of rain: ~34.5ppt • 30oN/S - high evaporation: ~36.7ppt • 50-60oN/S: lots of rain but cool: ~34ppt
The Montreal Protocol
• 1987, by 2009 ratified by every country in the world • Created deadlines for cutting back CFCs • Amendments also helped • Good example of a policy based on scientific evidence that worked • People realized how serious the problem really was.
Are We Safe?
• 2050: Mid-latitude areas back to pre-1980 ozone levels • 2075: Polar regions back to pre-1980 ozone levels
Open Ocean Permanent Upwelling Zones
• 3 Divergence Zones: 1. Tropical divergence 2. Another tropical divergence 3. Antarctic divergence • Upwelling → high nutrients, high productivity → big influence globally - fuels food chains
Depth and Temperature
• 3 main layers: 1. Mixed layer: 10s-100s of meters • Isothermal - constant temperature • Depth depends on mixing activity and season • Mid latitude open ocean: 300m; coastal 10m 2. Thermocline: 200-1000m • Where temperature drops rapidly 3. Below thermocline: >1000m • Cold, and stays that way (isothermal) • 75% of oceans is between 0-4 oC
salt life
• 30% of table salt comes from seawater (unless it's sea salt...) • Most common way of getting salt: • Seawater flows into shallow pools → let the water evaporate and collect the leftover salt • Usually needs a warm/hot climate • But can also freeze seawater - ice is fresh water, brine is under it - tedious and not cost-effective usually • Then refine it to get NaCl and some other salts • Provides 60% supply of Mg and 70% of Br • Other stuff is in there too: gold, silver, etc. but such low quantities that it would be ridiculous to mine it this way
The Saltiness of Saltwater
• 99% of dissolved salts are 6 ions: • Na+ , Mg2+, Ca2+. K+ , Cl- , SO4 2- • Na and Cl = 86% of ions • Conservative constituents of seawater - not removed or added by organisms • Other 1% are trace elements • Nonconservative constituents - used in biological and chemical processes • Like iodine in seaweed and shellfish
Residence Time
• = average time a substance remains in solution in the oceans • = total amount divided by rate of input (or output) • Can be short (few 100 yrs): Al, Fe, Cr • Can be long (millions of yrs): Na, K, Mg
Water Masses
• = large body of water with similar temperature and salinity • Temperature-Salinity (T-S) diagram - shows same densities at difference combos of T & S • Water type - particular T and S • Different combos of S and T can make the same densities • When water types mix = caballing → will sink (downwelling) • Occurs when surface waters converge
Storm Surge
• = rising of the sea surface during a hurricane • Caused by: 1. Pressure = intensely low at center - causes water to rise (5%) 2. Winds - spiraling towards center (95%) • Usually larger on side approaching land - land acts as dam • If hits during high tide = storm tide • Biggest threat to life and property (more than wind) • What else can influence storm surge?
Atmospheric Pressure
• = the force a column of air presses on Earth's surface • At sea level: 14.7 lbs/in2 • Low pressure - rising air; high pressure - sinking air • Affected by latitude and land vs. ocean
Reducing Global Warming: Geoengineering
• AKA climate engineering • 2 main methods: 1. Carbon Dioxide Removal (CDR) • What's good about it? • Bad? Problems or hurdles? 2. Solar Radiation Management (SRM) • Good? • Bad? Problems? • What does it not solve?
Ocean Acidification
• All that extra CO2 → more acidic oceans • Believed to drop 0.5pH by 2100 (5x more acidic!) • Big impact on things that build shells and exoskeletons
Small-scale Monsoon Effects: Land-sea breezes
• Along coasts or shores of big lakes • During summer: • Daytime - land is warmer than water → air rises (Low) → air over water replaces it = onshore breeze • Peaks in afternoon • At night - lands cools faster → land air replaces rising water air = offshore breeze • Peaks late night/early morning • Can smell land 30km sometimes • Helped with sailing: leave early in the morning with the wind, come home in afternoon with wind
El Niño-Southern Oscillation
• Anomalous climatic conditions • Centered in tropical Pacific Ocean • Occurs every 3-7 years and last about a year • We don't know how it starts • Atmosphere? Ocean? Both? Neither?? • Causes surface pressure at Indonesian Low to be much higher & South Pacific High to be much lower • → weakens or even reverses trade winds = Southern Oscillation • Moves warm water to eastern Pacific where it shuts down upwelling near Peru • Causes water to be warmer and higher (by about a foot) • Usually happens around Christmas, hence "El Niño"
Ekman Spiral and Ekman Transport
• As go down in depth, each layer moves even slower (& deflects more) → makes a spiral = Ekman spiral; to ~150m • Net flow is 90o to the right (in North) = Ekman transport • ** this only occurs in the top 150m or so • → does not affect deep water mixing, etc.
Surface Wind Bands
• Between 0-30oN/S - deflection toward equator = trade winds (NE and SE) • 30-60oN/S: Westerlies • 60-90oN/S: Polar easterlies
Wind Zones
• Between wind bands - lots of vertical motion of air • → uneven surface winds - NOT good for sailing • Doldrums - @ equator, rising air, calm winds • Horse latitudes - 30oN/S - calm seas, bad sailing • How it got its name: tales of tossing horses overboard to save water or eating them for food
Gases
• Big 2 in atmosphere: N2 and O2 : 99% of air • Seawater has a lot more CO2 than air • N2 is mostly inert (inactive), O2 and CO2 biologically important
Icebergs
• Big and irregular, ~12% floats above surface • Made from glaciers • Northern icebergs tend to drift south • Greenland - slide off from land (remember Titanic?) • Alaskan - tend to get stuck in channels • Usually castle bergs- look like towers • Southern icebergs tend to be flat (table bergs) and stay close → get stuck in current
Major Ocean Currents: Arctic
• Big clockwise gyre driven by polar easterlies • Centered over Canadian Basin • Fueled by Norwegian current, a little from Bering Strait
Measuring Currents
• Buoys - float at particular depth, can follow path • Florescent dyes - track from boat, air, space • Drift bottles - lots of bottles with postcards - time and location found • Problems? • Current meters: measure flow rate (propellor) and direction (vane) • CTD with flow sensors • Sound pulses • Measure change in sound frequency - water moving towards = higher frequency; away = lower = Doppler Effect
The Biological Pump
• Carbon cycling due to biological activity: • CO2 → organic C (photosynthesis) • → Consumption and/or decomposition (recycled) • Some gets deposited on sea floor • → Carbon is "pumped" to the sea floor
Carbonate as a Buffer
• Carbonate acts as a buffer - prevents fast or large pH changes • A buffer will add or remove H+ ions to bring it back to normal • Reaction: CO2 + H2O ↔ H2CO3 ↔ HCO3 - + H+ or CO3 2- + 2H+
Winds
• Caused by differences in air density (and thus pressure) • Unequal distribution of solar radiation • Presence/absence of water • Difference in surface material heating properties
Coastal Upwelling and Downwelling: Seasonal
• Changes in upwelling and downwelling when wind patterns change • Ex: on West Coast U.S.: • Summer: North winds, water movement to West (90o Ekman transport) → upwelling along coast; is why San Francisco fogs up so much in the summer • Winter: South winds, water movement to East → downwelling • Seasonal changes not common in S. hemisphere • Not much land
CFCs
• Chlorofluorocarbons • Developed in 1930s as a coolant in fridges, AC, etc. • Soon in everything: hairspray, fast food containers, etc. • Very stable → good for people, bad for atmosphere • UV breaks it down • Chlorine destroys ozone • This was known! But hard to change once it is already in place
Depth and Density
• Density depends on temperature, salinity, pressure • Increases with: lower temp, higher salinity, higher pressure (but mainly T and S) • 3 Density layers: • Mixed layer - surface to 10-100s of meters • Pycnocline - big change in density - usually matches thermocline • Below Pycnocline
Downwelling and Upwelling
• Downwelling - sinking surface water, brings O2 -rich waters to depth • Upwelling - rising deeper water, brings nutrients to surface - promotes photosynthesis • Thermohaline circulation can do this but so can surface currents • Convergence - when surface waters pushed together (winds or hitting coast) → downwelling • Divergence - winds blow waters away from coast or area → upwelling
Earth's Heat Budget
• Earth's average temperature remains fairly constant → means that heat loss ≈ heat gain • Incoming energy from sun - shortwave radiation • 70 units absorbed (51% by land) • 30 units reflected (20% by clouds) • But we need 70 units outgoing: • Long-wave radiation (see pictograph) • Ground - absorbs more heat than it radiates back out to space • Atmosphere - reflects more heat than it gains • Albedo effect - reflectivity of a surface
Surface Currents: Geostrophic Flow
• Eckman transport deflects parts of water inward (= Fc ) • This causes a bulge in the centers of the ocean gyres • Gravity pushes outward from bulge (=Fg ) • When Fc = Fg → geostrophic balance
Pacific Ocean Water Masses
• Few places with distinguishable masses • No large source of deep water (unlike Atlantic) • Very slow circulation = very long residence time (~2x Atlantic
Seawater pH
• H2O can dissociate into H+ and OH- • In pure water, concentration of both is 10-7 = neutral solution • More H+ = acidic; more OH- = basic (alkaline) • pH scale: 0-14; <7 acidic; >7 basic • Is a log scale (factors of 10): • Ex: a pH of 2 is 10x more acidic than pH of 3 • Rain (even drinking water) - slightly acidic (carbonic acid) • Rain usually ~5, but can be 3 = 100x more acidic! • Seawater - slightly basic (~7.5-8.5), especially at surface
Convergence and Divergence: Permanent
• High and Low pressure systems • Low: cyclonic winds, counter-clockwise = Ekman transport outward = divergence and upwelling • High: anticyclonic winds, clockwise = Ekman transport inward = convergence and downwelling
Effects of ENSO
• Highly variable! • May depend on size and temperature of the water • May cause droughts during one ENSO event, floods another • Usually: • Northern U.S. has warmer winters • Eastern U.S. gets more rain • Hurricanes tend to be less intense and fewer in number
HURRICANES
• How to build one: 1. Warm water: >27.8oC (82oF) 2. Strong low pressure system • Easily formed near equator - lots of rising air → lots of condensation → lots of heat released (latent heat) → causes air to rise → etc. 3. Coriolis - gives them spin • Can't form right on equator • Why not? • As long as a hurricane has these ingredients, it will keep getting bigger and stronger → Hurricanes are gigantic heat engines • Take one ingredient away or lessen it or ventilate the heat (wind shear does this), and it weakens
The Great Ocean Conveyor Belt
• Huge thermohaline conveyor belt of heat (Temperature and Salinity) • Remember all those water masses? (NADW, AABW, etc?) • This is how they move around the world • Round-trip: 1000 yrs
Anthropogenic CO2
• Human burning of fossil fuels and deforestation → increasing CO2 levels in atmosphere and oceans • Pre-Industrial Revolution: 280 ppm • But what are some natural sources? • September 20, 2020: 411.16 ppm • (+ ~2 ppm per year) • Keeling Curve: shows seasonality of CO2 levels • Low in Spring/Summer • High Fall/Winter
Water Scarcity
• Humans don't all live near abundant sources of water • Ex. Middle East • Some do, but can't access it or afford it • Developed countries: • Use a lot of water • High-tech ways of getting it • Developing countries...well....
People are Stubborn and Stupid
• Hurricanes are bad enough, but people can be even worse. • Many people refuse to evacuate. Then need to be rescued. • Huge burden on emergency crews. • Barrier islands take the brunt of hurricanes' wrath • We like to build on them. • Is that smart? • But who would give it up or turn it down? • Other examples of human nature: • Price gouging • Looting • Crime • Taking advantage of the system • Some good, too!
Winds (If Earth Stood Still)
• If earth was still and had no continents: • Warm air rises at equator; cold sinks at poles • 2 big convection cells: • Surface winds would go N→S and upper winds S→N in northern hemisphere • **remember winds are names for where they come from • Ex: A south wind is coming from the south and blowing towards the north
Dead Zones
• In July 2017 NOAA scientists found that the "dead zone" in the Gulf of Mexico was the largest ever recorded • 8,800 square miles (size of NJ) • In 2020: 2,117 square miles (smaller than Delaware) • Sounds great, right? • But due more to weather at time of data collection • Not due to lower N load
La Niña
• In between El Niño's • East Pacific colder than normal; west warmer than normal • Stronger trade winds • Surface waters off Peru unusually cold • Eastern Pacific dry weather • Floods in India and SE Asia
Structure of the Atmosphere
• In order of increasing height 1. Troposphere • Temperature decreases with altitude • Tropopause: minimum temperature zone • Warmed from heat radiation from surface and condensation of water vapor • Wind, rain, clouds are all here 2. Stratosphere • Temperature increases with altitude • Ozone - absorbs UV → increases temperature • "good" ozone; not like "bad" ozone near surface
The Monsoon Effect
• India and SE Asia • Summer - land is hot (L pressure), rising air replaced by warm moist air from the SW→ lots of rain = wet monsoon • Winter - opposite, north winds - dry monsoon • Was important for trade - had to time it right for sailing • Timing not as important today
Major Ocean Currents: Indonesia
• Indonesian Flowthrough • Western south pacific • LOTS of islands • Currents flow between them - mostly the remainder of equatorials • Transports lots of warm fresh(er) water to Indian Ocean
Dissolving Ability of Salts
• Ions - charged atom(s) • + charge = cation; - charge = anion • Salts in water are present as ions • Ionic bonds - metal to non-metal • Easily broken by water: water surrounds them, prevents from joining • → water is good at dissolving them
Sidenote: Extinction of the Giant Clam?
• Ivory is generally frowned upon → • "Jade of the Sea" - giant clams (Tridacna gigas) • ~10 yrs for females to mature (3 for males) • Ecologically important • Self-contained reef - even has zooxanthellae • Why giant clams? • Aphrodisiac if eaten (?) • Ivory hard to get • Carvings, shell trade • → Up to $12,000 per large clam • Protected by international trade laws • Applies only with permits, sales, exports • Doesn't help if sold domestically • Or smuggled
Latitude and Light Cycles
• Little variation near equator • Huge variation near poles (6 months of light/dark) • Due to sun migrating north and south
Current Volume Transport
• Measured in Sverdrups: 1Sv = 1million m3 /s • Variable - location, time of year, location within current • Gulf Stream: • ~30Sv in Florida Straits, increases to 80Sv near Cape Hatteras, then increases to 150Sv at 55oW • Higher in Fall, lower in Spring • Antarctic Circumpolar Current: 125Sv!
Solar Radiation Distribution
• Most intense at equator, least at poles • Solar constant - amount of energy per minute that would hit the surface if no atmosphere and at a right angle (same amount per area) • = 2cal/cm2 /min - only between 23.5oN/S • greater than 23.5o → get less energy per area • Also has more atmosphere for radiation to go through
Ocean Salinities
• Most seawater is 96.5% water and 3.5% dissolved ions (salts) • Salinity = amount of salt in water, in ppt (this is NOT percent!) • Surface salinity varies with latitude • Due to patterns of evaporation, freezing, runoff, etc. • High around tropics, low near equator and mid-latitudes • Low at river mouths, high in landlocked seas • Mediterranean Sea - 39ppt • Changes seasonally in polar areas • Tides in coastal waters
The Topographic Effect
• Mountains will affect wind patterns and therefore rain • Mountains block wind, forces it up where it cools, condenses = rain on windward side • → dry on leeward side = rain shadow • Ex: Washington Mountains: • On west - Olympic Rain Forest - 200" rainfall per year • On east - Rain shadow - 20" rainfall per year • Related to the orographic effect - control of precipitation patterns due to changes in elevation
Measuring ENSO
• Multivariate ENSO index = MEI • Measures sea surface temperature, surface pressure, surface-air temperature, wind speed, cloud cover • Positive values for El Nino's; Negative values for La Nina's; 0=normal • Useful, sometimes saves billions of $$, but still incredibly hard to predict!
Ozone
• Near ground ozone is a pollutant - smog - bad for lungs • Produced by VOCs and NOx + sunlight • In atmosphere it's good - protects from UV • If ozone dropped 50% → 350% increase in UV radiation reaching surface. Ouch. • "Hole" in ozone layer over Antarctica • Fluctuates year to year • Is slowly getting better • Problem due to CFCs → break down and Cl reacts with ozone and breaks it apart
Major Ocean Currents: Atlantic
• Northern Atlantic: • North Atlantic • North Equatorial • Gulf Stream • Canary • Labrador and East Greenland counterbalance Norwegian • Southern Atlantic: • South Equatorial • Brazil • Benguela • Weak Equatorial Counter-current
Major Ocean Currents: Pacific
• Northern Pacific: • North Equatorial • North Pacific • California & Kuroshio (not wind-driven, provide continuity of flow/conservation of mass) • Southern Pacific: • South Equatorial • Peru/Humbolt • East Australian (EAC) • Between these two Gyres: • Equatorial counter-current
Wind Bands
• Now, let's add the Coriolis Effect to global wind patterns • Air rises at equator, moves to poles, turns and sinks at 30oN/S • Moves along surface either toward equator or 60oN/S • Repeat again to poles or equator • → 3 convection cells on either side of equator (6 total)
Seawater Nutrients
• Nutrients are required for biological growth and maintenance • Plants and phytoplankton needs nitrate and phosphate, diatoms also need silica • N, P, and Si are in very low concentrations in seawater • Redfield ratio: C:N:P = 106:16:1 = ratio found in phytoplankton (and marine biomass in general) • With Si: C:Si:N:P = 106:40:16:1
CO2 and the Greenhouse Effect
• Ocean is biggest reservoir of CO2 ; atmosphere smallest • But atmosphere connects everything • Why is CO2 a greenhouse gas? • Lets in short-wave radiation from sun • Blocks and absorbs (traps) long-wave radiation from earth
The Constant Proportion of Seawater
• Oceans are pretty well-mixed • Currents, vertical mixing, waves, etc. • → ion ratios are the same worldwide, even at different salinities! • = principle of constant proportion • Only true for open ocean waters and major constituents
Salt Removal
• Oceans have been around 3.5BY, same salinity for 1.5BY • → input and output of salts must cancel out Removal: 1. Sea spray - but not permanent. Why? 2. Shallow seas getting isolated and evaporate → sedimentary deposits called evaporites 3. Ions react with things and precipitate to seafloor
Sources of Salt
• Originate from crust and interior of the earth 1. Crust: mostly cations from cooling magma, carried to sea by rain and rivers • Sidenote: most abundant ions in rivers are least abundant ions in ocean. Why? • The most easily dissolved ones are already there! 2. Interior: anions from mantle gases - volcanic eruptions release H2S, SO2 , Cl2 → dissolve in rain and return to ocean as Cl- and SO4 2-
Desalination: Semipermeable Membranes with Reverse Osmosis
• Osmosis - movement of water from high to low concentrations across a semipermeable membrane • Water moves from low salinity to high salinity • Creates higher pressure on high salinity side • Reverse osmosis - adds pressure to force water through membrane • Needs >24.5atm of pressure, usually ~100atm • Very popular - no thermal pollution, removes everything (bugs, etc.), fairly energy efficient • The bad news: that brine has to go somewhere and $$
Desalination: getting fresh water from seawater
• Three main methods: 1. Change of water's state: evaporate or freeze seawater 2. Ion exchange columns 3. Semipermeable membranes
Gas Distribution with Depth
• Oxygen Compensation depth - where O2 produced = O2 removed • Above it, excess O2 produced • What factors will cause it to change in depth? • Oxygen minimum zone - around 800m • O2 levels go up a little below it → less organisms there
Measuring O2 and CO2
• Oxygen: • Chemical reactions (we will do this in lab) • Probes - like a YSI or CTD with O2 sensor • Carbon dioxide: • Not much CO2 gas in seawater: • CO2 readily reacts with water to form carbonic acid (H2CO3 ) • → pH is a good indicator of CO2 levels
Western Intensification
• Peaks of mounds of water created by Ekman transport in ocean gyres not in center → skewed to west • Steeper slope on west side, gentle slope on east • → currents on west side tend to be faster, deeper, and narrower = western intensification of currents
Composition of the Atmosphere
• Permanent - don't really change • Variable - will change based on time and location • Density of air controlled by 3 things: • Temperature - warm = less dense • Humidity - high = less dense • Altitude - higher = less dense
Eddies
• Pockets of water with circular motion • Like whirlpools off main current • Warm-core eddies - rotate clockwise • Cold-core eddies - rotate counter-clockwise • Which would produce upwelling? How would this affect productivity? Fisheries? • Constantly form, move, dissipate • Help mix water • Shallow to very deep, may even reach sea floor • Can examine properties to tell where they're from: • Ex: "Meddies" from Mediterranean
A Briny Problem
• Recent study (2019) found for every 1L potable water produced, 1.5 L of concentrated brine is released into oceans • Very salty plus harmful metals, etc. • Effects? • Very dense → sinks and sits on ocean floor • Oxygen depleted (often hot, plus salty) • → remember saturation concentrations? • → kills marine life, especially benthics • Most desalintation in Middle East/N. Africa
Specific Heat and Heat Capacity: Differences Between Land and Sea
• Rock and soil have low specific heat → land has low heat capacity • How does this affect temperature fluctuations on land vs. sea? • How does the distribution of land and water affect temperature fluctuations in each hemisphere?
Issues with Water Use
• Saltwater Intrusion • If aquifers not recharged, saltwater into aquifer • Once it's in there, can't get it out • Big problem in CA, FL • CA pumped treated wastewater into aquifers to block saltwater • Others: • Disease • Famine • War • Death
Saturation Concentration
• Saturation concentration: maximum amount of gas that can be in solution • Affected by salinity, temperature, and pressure • Increase it by: • Lowering temp • Lowering salinity • Raising pressure
Sea Ice
• Sea ice = frozen seawater • Breaks into pancakes → may unite into ice floes (< 10km in any direction) • Ice floes move around, combine, split • If they become anchored to land → fast ice • If free-floating = drift ice • Continuous sea ice = pack ice
Impacts of Increasing CO2
• Seasonal - goes up in winter/fall (less photosynthesis, more decay) • Burning fossil fuels, etc. increasing CO2 levels • 2-4 oC increase over next 100 years • Melt ice caps and raise sea level 1m by 2100 • May change sea surface temperatures and disrupt currents → major changes to climate patterns
Desalination: Solar Stills
• Solar still - pond of seawater with dome on top • Water evaporates and collects on dome • Dribbles down sides into troughs • Very slow, but very cheap and low-energy costs • Can boil seawater too, but takes more energy • → but lower the pressure → lower b.p. = takes less energy to boil • Also useful in survival situations
Rotational Speeds
• Speed of rotation varies with latitude • Fastest at equator (~1000 mph) • Slowest at poles (zero) • Difference in rotational speeds doesn't affect things attached to land • But will affect clouds, planes, missiles, water, etc. • Only affects moving objects
Arctic Ocean Water Masses
• Split into basins by ridges • Density controlled more by salinity than temperature • Surface water from Bering Sea, melting sea ice, rivers
Temporary Convergence and Divergence: Langmuir Circulation
• Strong or steady winds at sea surface can create windrows - lines of foam and debris in the direction of the wind • These lines mark convergence zones (downwelling) of paired circular cells = Langmuir cells • Foam, seaweed, etc. are too light to actually be pulled down - is why we see lines at surface • In between the windrows are divergence zones (upwelling), but diffuse • The closer they are together, the shallower the thermocline • Short-lived and shallow (<10m) but help with mixing
Major Ocean Currents: Indian
• Strong seasonal shift • Summer - blows surface water to the east • Winter - to the west
Oxygen Levels
• Supersaturated - when concentration is above 100% equilibrium levels • When and where would this occur? • Hypoxic - water that is low in O2 • Anoxic - water that is devoid of O2 - only things that can go anaerobic for extended periods of time can survive in these places
Current Speed
• Surface currents move about 1/100th of wind speed that is 10m above them • But, speed also depends on diameter of the current • Would a current going through a narrow passage speed up or slow down? • Gulf Stream: up to 2m/s (5.6mph)
Depth and Salinity
• Surface salinity varies with latitude, weather, etc. • Halocline - drastic change in salinity • Sometimes constant with depth • Sometimes increases up to 1000m • High latitudes • Sometimes decreases with depth to 1000m • Low latitudes • Below 1000m almost always constant
The Coriolis Effect
• The apparent deflection of objects due to differences in rotational speeds of earth's surface • Northern hemisphere: deflect to the right • Southern hemisphere: deflect to the left • Greatest deflection at poles • Zero deflection at equator
Surface Currents: Ocean Gyres
• The major surface currents are due to trade winds and westerlies • Surface waters are deflected 45o • Net transport deflected 90o • Also deflect when reach edge of ocean basin • → Creates large gyres that rotate clockwise in N. hemisphere, counter-clockwise in S. hemisphere
Internal Mixing of Water Masses
• Turbulent processes help homogenize the oceans • Winds, currents, caballing, eddies, etc. • Diffusion too, but very, very weak • Vertical mixing is weak - buoyancy effects tend to return things to where they started • Horizontal mixing strong - requires much less energy
UV Radiation
• UV-A: sunburn, some damage, 50% reaches surface • Penetrates deeper • UV-B: DNA damage, cancer, 10% • UV-C: high-energy, helps form ozone, would be devastating to life, <1% • The shorter the wavelength, the more dangerous
Where else to get water: Aquifers
• Underground water source • Permeable rock/soil saturated with water • Naturally filtered • Only good if replenished! • Recharged through infiltration • Rain penetrating down into aquifer
Desalination: Ion Exchange
• Use resins that pick up ions • Only good with low salinities (less than brackish) • Need to be replaced periodically
Desalination: Semipermeable Membranes with Electrodialysis
• Uses electric field to move ions out of solution and through semipermeable membrane • Only good for low to brackish water
Surface Currents and Wind
• Water is ~1000x denser than air = has a lot of inertia • → less affected by day-to-day changes • Moving water is deflected from Coriolis, but is deflected even more because it has higher inertia compared to air • To the right of prevailing wind in N. hemisphere • Leads to a 45o deflection in surface water relative to wind direction
Most Notorious Hurricanes: Andrew
• When: August 1992 • Where: Miami, FL • Category: 5 • Pressure: 922mb • Max Winds:145kt • Facts: • Small storm surge - didn't have time to build up between Bahamas and FL • Also broken up by reefs and barrier islands • Major wind damage - lead to huge overhaul of building codes
Most Notorious Hurricanes: Katrina
• When: August 2005 • Where: Fort Lauderdale, FL then Louisiana • Category: 1(FL), 3(LA) • Pressure: 920mb • Max Winds: 110kt • Facts: • Costliest and most destructive in U.S. history ($200 billion; 1200 direct deaths) • Weakened after hitting FL, then swelled in warm Gulf of Mexico • Levees and dams failed → 80% New Orleans underwater • Most of the city is at sea level (cemeteries are above ground!) • Highest ever storm surge: 11.3 meters in MS
Most Notorious Hurricanes: Harvey
• When: August 25, 2017 • Where: Rockport TX • Category: 4 • Pressure: 937mb • Max Winds: 130mph • Facts: • MAJOR flooding - year's worth of rain in a week • 50 inches in Houston - NWS had to update its colors on maps! • 13 million affected, ~80 deaths • 1 st Category 4 to hit U.S. since Wilma in 2005
Most Notorious Hurricanes: Typhoon Tip
• When: October 1979 • Where: Japan • Category: 5 • Pressure: 870mb • Max Winds: 190 mph • Facts: • The most intense hurricane ever • Largest diameter ever: 1400 miles
Most Notorious Hurricanes: Wilma
• When: October 2005 • Where: South Florida • Category: 3 • Pressure: 950mb • Max Winds: 105kt • Facts: • Was most powerful hurricane ever recorded: • 882mb pressure, 173mph winds • Went from Tropical Storm to Category 5 in 24 hours!
Most Notorious Hurricanes: Patricia
• When: October 2015 • Where: Pacific coast of Mexico • Category: 5 • Pressure: 872mb • Max Winds: 215mph • Facts: • 2 nd most intense hurricane ever • Most intense in western hemisphere • Strongest sustained winds ever • Went from TS to Category 5 in 24 hrs • Few fatalities and damage (mostly rural) • Dissipated almost completely after making landfall
Most Notorious Hurricanes: Florence
• When: September 14, 2018 • Where: Wrightsville Beach, NC • Category: 4 (landfall as 1) • Max winds: 140mph • Effects: some wind damage, storm surge and epic rainfall did the worst • NC alone got ~9.6 trillion gallons of rainfall • Enough to cover entire state in 10 inches of water • Worst flooding came later as watershed drained water south into SC
Most Notorious Hurricanes: 1900
• When: September 1900 • Where: Galveston, TX • Category: 4 • Pressure: 936mb • Max Winds: 120kt • Facts: • They didn't name them back then • 8000-12000 killed - deadliest natural disaster in U.S. history • Leveled almost the entire city • Nearly 15 ft of water over the entire island! • No warning system
Most Notorious Hurricanes: Ike
• When: September 2008 • Where: Galveston, TX • Category: 2 • Pressure: 950mb • Max Winds: 95kt • Facts: • 2 nd costliest ($29.5 billion) • 20ft storm surge on Bolivar Peninsula
Most Notorious Hurricanes: Hugo
• When: September 22, 1989 • Where: South Carolina • Category: 4 • Pressure: 934mb • Max Winds: 120kt • Storm surge: 20 ft at Bulls Bay; 13 ft at Myrtle Beach
Seasonal Changes
• Winds go from high pressure to low pressure • Mid-latitudes: summer - land is warmer (low pressure) than ocean (high pressure) → sea breeze onto land • What happens in the winter? • Intertropical Convergence Zone (ITCZ) - area of highest surface temperature • Moves around from 10-20oN/S • This will be important when we get to hurricanes
Thermohaline Circulation
• With a stable water column, density increases with depth • What happens if denser water is on top? • Denser water sinks and will spread laterally when it hits a barrier • Thermohaline circulation - due to density differences caused by temperature and salinity differences • If same density over depth (isopycnal) - easily mixed
Measuring Salinity
• ppt - parts per thousand (concentration) • psu = practical salinity units (unit-less) • Based on conductivity of water (relates to # of ions) Most popular methods: 1. Taste it. (Not recommended!) 2. Hydrometer - reliable but annoying 3. Plastic Hydrometer - quick, not accurate 4. Refractometer - reliable, very accurate 5. YSI - extremely accurate, reliable, but $$$