Eric H. Christiansen Brigham Young University

The Climate System Atmosphere Composition, structure, circulation Ocean Composition, structure, circulation Climate change Regional Global

Composition of the Atmosphere Nitrogen, Oxygen and Argon make up 99.9% Unique in our solar system Oxygen Water Vapor

Composition of the Atmosphere Ar, Ne, He, Methane are minor constituents Some minor gases absorb light energy and help retain heat Water vapor CO 2 Ozone Methane

Stratosphere – T increases with altitude due to ozone – Does not readily mix with troposphere Troposphere – T decreases with altitude – Turbulent flow of air, variable humidity Mesosphere – T decreases with altitude Thermosphere – T increases again with altitude - UV absorbed – Charged ions formed Magnetosphere Structure of the Atmosphere

Uneven distribution of incident solar radiation

Atmospheric Circulation Incident solar radiation produces differential heating of the Earth (sphere) Air masses move to balance global T Warm air rises while cold air sinks Earth’s rotation deflects the pole to equator flow direction Coriolis effect

Global Water Movement Atmospheric circulation moves water Evaporation increases with T Warm air holds more water vapor At Equator warm, wet air rises and moves towards poles as cold air sinks Cooling air masses may produce precipitation

The Climate System Atmosphere Composition, structure, circulation Ocean Composition, structure, circulation Climate change Regional Global

Global Water Movement Evaporation - Precipitation balance High “evaporation” areas become sources Certain oceanic areas supply a large portion of water vapor to the atmosphere Prevailing winds carry water vapor over continents

Composition of Seawater Salinity Total of all dissolved constituents in seawater ~ 35 g/kg on average Dominated by Na + and Cl - ~ 30 g/kg of NaCl aq Varies globally based on rainfall, river, and evaporation patterns

Temperature of Seawater Water has a high heat capacity Large influence on Earth’s climate Average T of 3.6 o C, but varies widely Layered structure Density varies with T Warm surface water vs. cold deep water Sea ice

Motion of the Ocean Water in the ocean is in constant motion Movement may be fast to extremely slow Driven by: Wind Variations in density T and salinity Surface Temperature

Wind Driven Currents Wind impacts the surface layer Prevailing winds push water in one direction Water is deflected by land masses Surface water currents form roughly circular patterns within a ocean basin

Density Driven Currents Thermohaline circulation T and salinity control density of seawater Cold water density > Warm water High salinity density > Low salinity Polar oceans have colder waters Polar regions have lower rainfall, increasing salinity

Density Driven Currents Dense surface waters in polar regions sinks Currents flow along the sea floor Extremely slow moving ~ 1000 year cycle Easily crosses the equator Maintains T and chemical balance within the ocean

AS Bower et al. Nature 459, (2009) doi: /nature07979 Float trajectories n the North Atlantic.

Global Oceanic Circulation Entire ocean is slowly mixed Wind driven - shallow Density driven - deep Coastal upwelling Flow paths may be long, covering the entire globe

Connections between Ocean and Atmosphere

Climate Zones Climate impacts geologic processes Rates of weathering Soil development Modes of erosion and transport Sedimentary rocks record ancient climates

Climate Zones

Tropical Climates High average T > 20 o C High precipitation - up to 2 m/yr Development of rain forests Large river systems Deeply weathered soil profiles

Desert Climates Precipitation < evaporation Total precipitation < 25 cm/yr T varies from very hot to very cold Slow rates of weathering Erosion by wind Evaporite deposits

Temperate Climates Range between 35 o and 60 o N & S of the equator T ranges throughout the year Precipitation may fall at any time Large rivers may form Moderate weathering & rich soils

Polar Climates Regions N & S of 60 o latitude Average T < 10 o C, below 0 o most of the year Low precipitation, often classified as deserts Low rates of weathering Glaciers

Climate Change Climate change may be dramatic or minor T has been relatively constant over geologic time Small changes in T may cause large changes in climate

Regional Climate Change Position of continents in global climate zones dictates regional climate Continents move through geologic time Sequences of sedimentary rocks record past climates

Global Climate Change Change in the size of global climate zones Expansion and contraction of tropical, temperate or polar zones Temperature is critical component Factors that change T are most important

Global Climate Change T is controlled by: Changes in solar output Composition of the atmosphere Reflectivity of the Earth Ocean circulation and position of continents Changes in the Earth’s spin or orbit

Human Effects on Atmosphere Changes in atmospheric composition Change of greenhouse gas concentrations Absorb certain wavelengths of light and heat the atmosphere CFCs and ozone depletion Rate of human impact vs. response of Earth’s systems is not well understood

Greenhouse Heating

Global Climate Models: The Future?

Effects of Global Warming Sea level rise Expansion Melting ice Shift in climate/agricultural zones Enhanced storms? Enhanced disease?

Human impact on climate change Changes in atmospheric composition CFCs and ozone depletion Change of greenhouse gas concentrations Rate of human impact vs. response of Earth’s systems is not well understood Human Effects on Atmosphere

Ozone Hole Over Antarctica

The atmosphere and ocean form a global system of moving water and gas. It is driven by solar heat and is responsible for Earth’s climate patterns. The atmosphere is an envelope of gas surrounding the entire globe. It is in constant motion and interacts with the oceans. The uneven distribution of solar energy from the equator to the poles results in uneven distribution of temperature, moisture, and wind. Water in the oceans exist in two major layers, (a) a thin surface layer of warm water and (b) a thick mass of colder water below. Sea ice occurs in the upper layer in the polar regions. Movement of the upper layer of ocean water is driven by the wind and density differences drive flow in the deep ocean. Climatic zones vary with latitude. Climatic change may result from global changes in temperature. Global warming and destruction of the ozone hole are examples of the role people play in climate change.

Atmospheric Pressure Air has very low density Column of air exerts pressure at sea level ~1 bar (1 kg/cm 2 ) Atm. P drops rapidly with altitude 0.5 bar at ~ 5600 meters elevation bar at 80 km

Water Vapor Atmospheric water content varies Added by evaporation Removed by precipitation Residence time in atmosphere is very short Water vapor traps heat Clouds reflect incident solar radiation

Coastal Upwelling Coriolis force causes surface currents to turn Surface water may move away from a coastline Cold, deep water rises to replace it Deep waters are often nutrient rich