Chemical and Physical Properties of Seawater Chapter 3, p

Specifics Properties of water Ocean Circulation Waves and Tides Brainstorm with a partner!

Unique properties of water All 3 states of matter on Earth Very polar molecule Hydrogen bonding

Evaporation Liquid  Gas Hydrogen bonds broken Density and temperature

Unique Nature of Water With lower temperatures, water molecules move closer to one another. Imagine a gallon bucket of seawater. At 75 degrees, the molecules are further apart than when this same gallon of water is at 35 degrees. When molecules are closer together, the substance is said to have more density. Higher density = heavier, even when volume is the same.

Unique properties of Water So… cold water sinks below warmer water Colder water also holds more oxygen than the same volume of water. Great for all those organisms living at the ocean floor. Now, even though colder water is more dense than warmer water, this changes when the water gets cold enough to freeze. Now, even though colder water is more dense than warmer water, this changes when the water gets cold enough to freeze. Ice floats and acts as barrier to cold air for marine organisms living in the water.

Temperate and State Less dense as a solid than a liquid. Habitat and insulation for organisms H + bonds result in higher melting and freezing temp.

High Heat Capacity Water is able to absorb a lot of heat with a relatively small increase in temperature HIGH heat capacity – amount of heat needed to raise a substance’s temperature by a given amount Important for marine organisms Not exposed to rapid changes in temperatures

Latent heat of melting Latent heat of melting – the amount of heat required to melt a substance Absorbs A LOT of heat when it melts – Hydrogen bonds break, but motion of molecules does not speed up until all of the ice melts. It takes A LOT of energy to break hydrogen bonds! Without H + bonds, ice would melt at about -90°C instead of 0°C

Water Cycle

Properties of Seawater Water is the universal solvent Ion dissociation

Seawater Salinity – total amount of salt dissolved in seawater Not just Na + and Cl - Lots of salts! See p. 48, Table 3.1 Where do the salts come from?

Where might ion concentrations of seawater differ from the normal amounts?

Salinity, Temperature, Density More salty = More dense Lower temperature  more dense Measuring temperature and salinity at specific points in the ocean – Niskin bottles Let’s take a look! Let’s take a look!

Temperature Profile Temperature, salinity, other physical characteristics and even plankton can be sampled at several depths at once

SST Satellite Images Current Conditions

Temperature and Salinity

SST of NE coast of the United States. Do you know the current?

Dissolved Gases Oxygen (O 2 ) – not very soluble Most released through photosynthesis Amounts also dependent upon respiration Carbon Dioxide (CO 2 ) – more soluble 80% of dissolved CO 2 is in ocean Nitrogen (N 2 ) Exchange occurs at surface of water Atmosphere to ocean Gas dissolves best in cold water

Oxygen Content of Ocean High oxygen content near the sea surface Low oxygen at mid-depth Increase in oxygen in the water ~ 1 km water below sea level

CO 2 in the Ocean FACT: 80% of the world’s CO 2 is found in the ocean. How is this affecting our oceans?

CO 2 Emissions CO2 is much more soluble than oxygen CO2 makes up more than 80% of the dissolved gas in the ocean, compared to less than 0.04% of air Ocean stores more than 50x as much total CO 2 as the atmosphere. Amounts of CO2 in the oceans are increasing.

Light Conditions CO 2 + H 2 O + sun energy  C 6 H 12 O 6 + O 2 C 6 H 12 O 6 + O 2  CO 2 + H 2 O + energy Must have the right light conditions to fuel photosynthesis! Light levels change with depth.

Visible Light Spectrum

Photos courtesy of www. science.nasa.gov Colors of the Ocean

Depth of 30 m: Only blue light remains: (a)Under natural lighting this sea star appears light blue, with the tips of the arms almost black. (b)A flash reveals the sea star’s true colors.

1. Photic zone – sunlit, 200 meters below the surface of the ocean 2. Twilight zone - from about meters below the surface. 3. Abyssal zone – no sunlight, from meters below the surface to the bottom of the ocean. Light Zones

Light Penetration of Surface Waters

Gathering Data

Pressure in the Ocean Organisms on land are under 1 atm (14.7 lbs/sq in or psi) at sea level. The weight of all the air above them. Marine organisms are under the weight of water AND the atmosphere. Since water is much heavier than air, marine organisms are under much more pressure than those on land. As the pressure increases, gases are compressed. Gas-filled structures inside organisms like air bladders, floats, and lungs shrink or collapse. Limits depth range of organisms We need special equipment to go deep or special instruments that can withstand pressure

Pressure in the Ocean

Ocean Circulation Currents move ocean waters around the world’s oceans at different depths (Ocean Conveyer Belt) Ocean Conveyer BeltOcean Conveyer Belt Waves, currents, tides, and gyres Wind patterns Ultimately driven by sunlight energy Currents circulate heat, nutrients, pollution, and organisms Drives Earth’s climate New Gulf Current

Winds As sunlight heats air, air rises. Cooler air rushes in to take the place of air that has risen. This movement is the source of winds. Ever notice how the winds at the coast are stronger during the day than at night? Winds created in this manner continuously at the equator are known as the Trade Winds. The Westerly's in the mid latitude and the Easterlies at the poles are less consistent than the Trade Winds.

Air near equator is warmed by solar heating and rises. Air from higher latitudes moves in over the Earth’s surface to replace the rising air, creating winds. The TRADE WINDS are deflected by the Corliolis effect and approach the Equator at an angle of about 45°. Trade Winds 30°S 30°N Doldrums

The major wind patterns are created by the rising of sun-warmed air and the sinking of cold air. How do the continents effect the wind patterns? Global Wind Patterns

Major Surface Currents

The Coriolis Effect The Coriolis Effect If the Earth did not rotate on its axis, the atmosphere would only circulate back and forth between the poles and the equator

The Coriolis Effect Because the Earth rotates on its axis, circulating air is deflected toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere. This deflection is called the Coriolis effect.

Wind Patterns Winds in atmosphere are driven by heat energy from the sun. Equator is warmer than poles – more heat energy absorbed here Less dense hot air rises Cooler air replaces it Wind is formed! Remember, winds to not travel straight, they are bent by Coriolis Effect

If the ocean current is regarded as layered, then each deeper layer moves more slowly than the overlying layer. Ekman Transport

Ocean Gyres Created by wind-driven surface currents Moderate climate by bringing warm water north and cold water south

Ocean Circulation In some locations, large volumes of water may sink or rise. Water sinks due to changes in temperature and salinity – this is known as an area of down-welling. Down-welling brings gases from the surface to deeper layers. Areas of upwelling come from currents that push deeper waters toward the surface. Nutrients are much more plentiful in the deeper layers, so these areas of upwelling are beneficial for organisms in an upwelling area.

Thermoclines Depth profiles for salinity, temperature, and density What is a thermocline and how does it develop? Seasonal vs. permanent thermoclines

Temperature Profile Stable water column = less dense shallow and more dense deeper Unstable water column = surface water sink and mixes with deeper water DOWNWELLING Polar regions in winter

Ocean Mixing These two water masses originate at the surface in the extreme North and South Atlantic, then sink and spread along the bottom.

Thermohaline Circulation The movement (circulation) of water in the ocean over great distances that is driven by changes in density Changes in density determined by temperature and salinity. “Fingerprint” of the water mass is how currents are tracked

Circulation of the Ocean The Great Ocean Conveyor – Global current pattern Deep circulation of the oceans is part of the global pattern known as great ocean conveyor. This constantly replenishes the oxygen supply to the depths.

Waves - Dependent upon the wind – longer and faster wind = larger wave - Water particles do not move along with a wave but instead move in circles. When under the crest they move up and forward with the wave, then they are pulled back down. As wave after wave passes, the water and anything floating in or on it moves in circles.

Waves As waves near the shore (shallower water), the bottom of the wave “drags” the bottom. Forces waves to slow and move closer together (short wavelength) The “drag” causes the wave crest to fall over - we call this a wave break. The surf caused from breaking waves displaces lots of sand which affects the organisms living there. Influence of the bottom causes the particle motion to flatten out into a back and forth movement known as surge

Fetch - the span of open water over which the wind blows Fetch is important in determining the size of waves Wind starts the wave which eventually settles out into a swell as it gets farther from the source of wind. Waves

What kind of waves are these?

Tides Gravitational pull of the moon and sun and by the rotations of the earth, moon, and sun. The moon and earth are held together by gravitational attraction. The moon’s gravitational pull is strongest on the side of the earth closest to the moon. Centrifugal force produced by the earth’s motion causes water to bulge outward, away from the moon. On the side of the earth closest to the moon, the gravitational pull overcomes the centrifugal force and pulls the water into a bulge toward the moon.

How does a grunion (Leuresthes tenuis) use the tide?Leuresthes tenuis

Because the moon moves while the earth is rotating, a full tidal cycle takes 50 minutes longer than the 24 hrs it takes the earth to make a complete rotation. Tides

1. Spring Tide - The tidal bulges are largest, and therefore the tidal range is greatest, when the moon and sun are in line - new and full moon. 2. Neap Tide - Tidal ranges smallest when moon and sun are puling at right angles, which occurs when the moon is in quarter. Tides

Semidiurnal tides – 2 high tides and 2 low tide per day Bay of Fundy How tides workTides

Worldwide distribution of semidurinal (2H, 2L), mixed semidiurnal (2H and 2L of different heights), and diurnal (1H, 1L) tides. Tides