The Origin and Evolution of the Marine Environment

The Origin and Evolution of the Marine Environment (MSCI*112)

Contact Information

  • Instructor: Prof Stewart

  • Phone: [Not Provided]

  • Email: jstewar6@coastal.edu

  • Office Location: Science II 221

The Climate System

  • Definition of Weather:

    • Describes atmospheric conditions (e.g. wind, temperature (T), and pressure (P)) over a short period of time.

    • Focuses on instantaneous or short-term weather conditions.

  • Definition of Climate:

    • Represents average Earth surface conditions and their variation over longer periods.

    • Important for understanding changes in climate over time.

Climate Distribution

  • Climate Zones:

    • Tropical

    • Arid

    • Temperate

    • Boreal

    • Polar

Consequences of Climate Change

  • Global warming/cooling, sea-level rise/fall, and changes in weather patterns.

  • Importance: The study of Earth’s climate system is essential for the well-being of life on Earth.

Components of the Climate System

  • Main Spheres:

    • Atmosphere: Contains nitrogen, oxygen, argon, water vapor, carbon dioxide, and other greenhouse gases.

    • Hydrosphere: Includes oceans, lakes, rivers, and glaciers.

    • Continental water is significant for weathering processes and sediment movement.

    • Biosphere: Encompasses all organisms affecting climate through respiration and photosynthesis.

    • Lithosphere: Involves the Earth's crust and upper mantle.

    • Cryosphere: Comprises glaciers, sea ice, and snow.

Energy and Climate

  • Mass in the five spheres is in constant motion, necessitating energy.

  • Energy Sources:

    • Solar radiation

    • Earth’s internal heat

Solar Radiation

  • Incoming solar radiation is balanced by reflected solar radiation and outgoing radiation.

  • Energy Imbalance: Leads to changes in the Earth's surface temperature (cooling or warming).

  • Distribution of Absorbed Energy:

    • ~47% absorbed by Earth's surface

    • ~23% reflected by clouds

    • ~23% absorbed by clouds

    • ~7% reflected by Earth's surface (Albedo phenomenon).

Outgoing Radiation

  • Distribution of outgoing radiation:

    • ~17% from Earth's surface radiation

    • ~83% from the atmosphere

    • Most surface radiation is absorbed and re-emitted by greenhouse gases.

Greenhouse Gases

  • Primary Greenhouse Gases:

    • Carbon dioxide (CO2), Methane (CH4), Water vapor, and Nitrous oxide (N2O)

  • Impact of Greenhouse Gases:

    • Without greenhouse gases, Earth's average temperature would be ~ -18 °C.

    • Concentrations of greenhouse gases have increased by 40% since industrialization, with levels higher than any time in the past 800,000 years.

Atmosphere Composition

  • Composition by volume:

    • 78% nitrogen

    • 21% oxygen

    • 1% trace gases (including CO2 and H2O)

  • Layers of the Atmosphere:

    • Troposphere: Contains 80% of air mass and 99% of water vapor. Temperature decreases with altitude.

    • Stratosphere: Houses ozone (O3) and is stratified in temperature with no convection.

    • Outer Atmosphere: Temperature decreases upwards, very frigid conditions.

Atmospheric Dynamics

  • Air movement is a key process for energy and water redistribution on Earth.

  • Duration for an air parcel to circle the globe is about one month.

Atmospheric Circulation

  • At the Poles:

    • Sun's rays strike at an angle, spreading heat over larger areas, resulting in colder temperatures.

  • At the Equator:

    • Sun's rays are nearly perpendicular, concentrating heat, leading to cloud formation and rain.

Hydrosphere

  • Components:

    • All liquid water in oceans, lakes, rivers, and groundwater.

    • Water cycle is vital for weathering and sediment transport.

  • Ocean Circulation:

    • A water parcel takes ~300 years to circle the ocean.

    • The hydrosphere is interlinked with the atmosphere and biosphere.

Thermohaline Ocean Currents

  • Also known as the Great Ocean Conveyor Belt, impacting heat distribution and climate.

Impact on Sea Level

  • Water exchange between continents and oceans influences sea level and the extent of the cryosphere.

  • Cryosphere:

    • Comprises ice sheets, ice caps, glaciers, and frozen lakes.

    • Holds approximately 75% of Earth's fresh water.

    • Average residence time of ice: ~20,000 years.

Lithosphere

  • Land surface processes interact with solar energy absorption and promote weathering, affecting CO2 levels in the atmosphere.

Biosphere

  • The biosphere impacts climate by removing CO2 and releasing O2 through life processes.

The Greenhouse Effect

  • Solar energy is emitted as visible light, infrared, and ultraviolet radiation.

  • The annual energy balance is maintained at approximately 342 W/m², with the planet absorbing and radiating this amount to sustain equilibrium.

Feedbacks in the Climate System

  • Positive Feedback: A change in one component causes another component's response that amplifies the original change.

  • Negative Feedback: A change leads to a response that counteracts the original change.

Climate Change Concepts

  • Without greenhouse gases, solar energy would escape into space, significantly reducing Earth’s temperatures.

  • The greenhouse gases trap solar energy, creating a climatic effect that warms the planet by approximately 33°C.

Flow of Energy in the Climate System

  • Incoming Solar Radiation: 340 W/m²

  • Reflected Solar Radiation: 29%

  • Outgoing Infrared Radiation: 71%

Proxy Records of Climate Change

  • Data sources include:

    • Observational records

    • Marine sediments

    • Ice accumulations

    • Growth rings from trees and corals

    • Lake varves and sediments

    • Speleothems (cave formations)

Long Term Climate Variations

  • Climate has changed periodically between cold and warm phases roughly every 100,000 years, aligned with CO2 and CH4 fluctuations.

  • Milankovitch Cycle Theory:

    • Changes in Earth’s orbit shapes solar energy incidence.

    • Types of cycles:

    • Eccentricity (approx. 100,000 years)

    • Obliquity (approx. 41,000 years)

    • Precession (approx. 23,000 years)

El Niño and La Niña

  • El Niño: Characterized by warm sea surface temperatures (SST) in the central/eastern tropical Pacific.

  • La Niña: Defined by cool SST in the tropical eastern Pacific.

Impacts of El Niño and La Niña

  • El Niño Consequences:

    • Droughts in various regions (Australia, Africa, Brazil, Indonesia)

    • Floods in other areas (Peru, southern USA)

  • La Niña: Leads to intensified weather patterns, stronger trade winds, and impacts on rainfall distribution.

Carbon Cycle

  • Pre-industrial CO2 levels were 280 ppm; increased to 370 ppm by 2000.

  • Human activities produce significant carbon emissions, impacting weathering, respiration, and chemical reactions within systems.

Human Perturbations

  • Fossil fuel burning, deforestation, and land-use change contribute to increased atmospheric carbon levels.

  • New plant growth and air-sea exchange help sequester some carbon, but a net atmospheric increase is observed annually.