Ocean Water Life Ocean Water Life The Ocean

Ocean Water & Life

Ocean Water & Life • The Ocean Floor • Composition of Seawater • Ocean Temperature & Density Variation

PSCI 131: Ocean Water & Life Review • What are these features called? • What happens at these locations? B A Mid-Ocean Ridge (Seafloor spreading) New ocean crust is formed Trench (Subduction Zone) Old ocean crust is destroyed

PSCI 131: Ocean Water & Life The Ocean Floor

PSCI 131: Ocean Water & Life Ocean Life and Ocean Features Certain types of ocean life flourish in different ocean features. Hydrothermal vents (deep sea) Continental Shelf (shallow water)

PSCI 131: Ocean Water & Life Composition of Seawater

PSCI 131: Ocean Water & Life Composition of Average Seawater Salinity – total amount of solid material dissolved in water Ratio of the mass of dissolved substances to the mass of the water sample. per mille (per thousand)

PSCI 131: Ocean Water & Life Composition of Normal Seawater • Salt sources Minerals from the continents Undersea volcanism

Questions • Where do icebergs originate? • If the iceberg melted, would the water be fresh or salty? • If icebergs melt, do you think ocean surface salinity is affected? If so, how?

PSCI 131: Ocean Water & Life Processes Affecting Salinity • Total mass of salt in open oceans doesn’t change, but salinity does • Since salinity = mass of salt / mass of water • So, water must be added/removed for salinity to change

PSCI 131: Ocean Water & Life Processes Affecting Salinity • Salinity increases if water is removed – Evaporation – Sea ice formation

PSCI 131: Ocean Water & Life Processes Affecting Salinity • Salinity decreases if water is added – Precipitation – Runoff (rivers) – Sea ice melting – Icebergs melting

PSCI 131: Ocean Water & Life Global Salinity Variation • Salinity varies by latitude • Areas that have high evaporation rates = high salinities (around 30 degrees N or S)

Think Pair Share • Name two acids. – What happens to a material when it touches an acid? • Name two bases. – What happens to a material when it touches a base?

Ocean Acidity • Rising CO 2 in atmosphere impact chemistry of ocean – About 1/3 of humangenerated CO 2 ends up dissolved in ocean – p. H drops, seawater becomes more acidic • Impacts on ocean life: – Microbes and corals have trouble building hard parts from Ca. CO 3 because acidic water dissolves Ca. CO 3

PSCI 131: Ocean Water & Life Ocean Temperature and Density Variations

Temperature and Density • Ocean Temperature and Density influence: – Deep-ocean circulation – Distribution and types of life • Both vary with depth

What happens to the temperature of the ocean as you go deeper in the water?

Temperature • Surface water is heated by the Sun – Usually warmer than deeper water • Due to varying amount of solar radiation at various latitudes, surface water can be warmer/cooler. – Low latitudes • High temperature at surface • Rapid decrease in temperature with depth (thermocline) – High latitudes • Cooler surface temperatures • No rapid change in temperature with depth

PSCI 131: Ocean Water & Life Temperature vs Depth Warm latitudes Cold latitudes

PSCI 131: Ocean Water & Life Thermocline • Exists between about 300 -1000 m of depth – (Below 1000 m temperature remains relatively constant all the way to the ocean floor. ) • Rapid decrease in water temperature with increasing depth • Exists year-round in tropics/subtropics • Never appears in subpolar/polar latitudes • Seasonal in temperate latitudes

What is density?

PSCI 131: Ocean Water & Life Ocean Water Density • Density = mass per unit volume – “How heavy something is for its size” • Determines water’s vertical position in ocean • Controlled by temperature and salinity (thermohaline) – Higher temp = lower density (expanding water) – Higher salinity = higher density • Temperature has the greater influence – Only in polar climates where temp is relatively constant does salinity significantly affect density

Variation by latitude • Low-latitudes – Low density at the surface – Density increases rapidly with depth (pycnocline) because of colder water • High-latitudes • High-density (cold) water at the surface • Little change in density with depth

PSCI 131: Ocean Water & Life Density vs Depth Warm latitudes Cold latitudes

PSCI 131: Ocean Water & Life Pycnocline • Exists between 300 -1000 m • Rapid increase in water density with increasing depth • Mirror image of thermocline – Temperature has stronger influence on density than salinity • Gravity prevents higher-density water from rising spontaneously and mixing with overlying less dense water – Barrier to mixing between surface and deep water

PSCI 131: Ocean Water & Life Ocean Water Layering • In regions where a thermocline is present – Surface mixed zone: warm, well-circulated • Mixed by waves as well as turbulence from currents/tides • Thickness and temp of this zone will vary due to latitude (thicker near equator)

PSCI 131: Ocean Water & Life Ocean Water Layering • In regions where a thermocline is present – Transition zone: • Location of thermocline and pycnocline

PSCI 131: Ocean Water & Life Ocean Water Layering • In regions where a thermocline is present – Deep zone: • Sunlight never reaches • Water temperatures are just a few degrees above freezing • Water density remains high and constant

PSCI 131: Ocean Water & Life Ocean Water Layering • If no thermocline, then no layering – Polar, subpolar, temperate (in winter)