Oceanography - Chapter 1 - An Ocean Planet

Influence of early fluids on earth formation

• Fluids allowed for density stratification

  • Dense elements sinks, while less dense ones rise. This helps for Earths center and surface.

Origins of the moon

• Formed 10s of millions of years after Earth after a major Collison happened with Earth and rock crust ejected to form the Earth

How did the early atmosphere form?

• Intense volcanic avtivity that caused outgassing

  • Gasses like H20 and CO2 that were trapped in the earth got released

  • Importantly there was no oxygen

How did the ocean form in an early atmosphere?

• As the Earth’s surface began to cool, the water vapor in the atmosphere condensed, and became liquid water.

• The water accumulated and also dissolved elements from rocks like Salt that eventually formed our Earth’s oceans.

What unique conditions allow Earth to maintain it’s liquid ocean?

• Relatively fast rotation → decreases extreme temperature differences between day and night.

• Strong magnetic field → deflects solar wind, helping protect Earth's atmosphere.

• Nearly circular orbit → reduces large variations in incoming solar radiation and therefore seasonal temperature extremes.

• The right amount of atmospheric CO₂ → helps maintain temperatures within the range where water can remain liquid through the greenhouse effect.

What kind of early live developed in the oceans?

Life likely developed in the oceans around 3.5 bya when the atmosphere had no O₂. Early organisms may have relied on chemosynthesis at hydrothermal vents. Organisms later became photosynthetic, adding O₂ to the atmosphere around 1–2 bya and eventually allowing more complex life to develop

Development of more complex life in the oceans over time?

• Earth’s ocean and atmosphere stabilized ~ 1 BYA allowing for the development of more complex life

  • Sponges + Jellyfish: 700 MYA

  • Fishes: 500 MYA

  • Land Plants: 430 MYA

  • Mammals: 220 MYA

Do other worlds have Oceans?

• Jupiter’s Moon Europa

  • May have huge liquid ocean underneath frozen ice

• Mars

  • Shows signs that a ocean once existed there (smooth rocks and gullies)

• Saturn’s Moon Titan

  • Ocean of liquid hydrocarbons

Greenhouse Effect

Incoming solar energy is mainly visible light. Earth's surface absorbs some of this energy and re-radiates it as longer-wavelength infrared (IR) radiation. Greenhouse gases absorb and re-radiate some of this outgoing IR, keeping Earth warmer. Increasing greenhouse-gas concentrations strengthens this effect and contributes to climate change

What percent of excess heat is stored in oceans?

90%

• And as a result we’ve seen greater temperature increases on land than the ocean]

• But because oceans can absorb so much excess heat, they has a greater heat gain than on land

What region of the world is experiencing the greatest warming?

The arctic

• In part due to a positive feedback loop and arctic amplification

Modeling

Models are simplified representations of real systems that use equations to describe relationships and make predictions. Scientists conceptualize the system, assign parameters and equations, test the model against observations, and validate it using independent data. Modeling is especially important in oceanography and climate science because ocean-atmosphere systems are complex, interconnected, and often nonlinear

Modeling - Conceptualization

• Describe system as a series of boxes (how to represent the system

  • Could be spatial areas, trophic levels, nutrient sources, etc

Modeling Parametrization

• Assigning values to your boxes and using equations to describe connections

  • Relationships between variables can be linear or non linear

  • Test your models using preexisting data sets to see if it can reproduce results and then adjust as needed

Modeling - Validation

• Testing your developed model with an independent data set

• This can highlight if the model actually is representative of the underlying processes

Linear modeling

• One parameter changes in director proportion to another

Non linear modeling

• Parameter relationships are not proportional and may only occur at extremes

  • Could be linear at portions of the curve, and non linear at other portions

• Non linear systems are very unpredictable

  • Changing one parameter could set an new equilibrium or crease chaos

  • Very sensitive to small changes

Positive Feedback loop

• Amplifies a change, causing the original effect to become stronger.

• Example: Warming → sea ice melts → more heat absorbed → more warming

Negative Feedback loop

• Counteracts a change, reducing or slowing the original effect.

• Warming → more evaporation → more clouds → more sunlight reflected → less warming.

Ocean acidification

happens when the ocean absorbs CO₂ from the atmosphere, which causes ocean pH to decrease through carbonate chemical reactions.

• ocean pH has fallen from about 8.2 to 8.1 over the past 200 years, representing about a 30% increase in acidity.

Negative impacts of ocean acidification

• Decreases the rate of coral production, and makes them more susceptible to temperature bleaching

• Prevents the growth of zooplankton and shellfish shells (it messes with the chemistry of the calcium carbonate formation)

Deoxygenation

• A decrease in the ammount of dissolved oxygen in the water

• Two Main causes

  • Warmer water holds less O and ocean temps are rising

  • Eutrophication causes large surges in algae photosynthesis, then O absorbing decomposition (caused by excess nutrients)

As temperatures rise stratification…?

Ocean stratification increases, meaning warm, less salinated, top waters are becoming further seperated from the deep, cold, salt waters.

• Results in stronger pyncocline between the surface and deep layer

• Also less mixing of nutrients and oxygen to the surface from the depths

Pycnocline

is the zone where density changes rapidly with depth.

Sea Level Rise

• Increased by 3.2 mm/yr from 1993-2010 (~2 in)

• Predicted Increase of 1-8 ft by 2100 (Chas ~ 20 ft above sea level)

• Causes:

  • Thermal expansion of H2O molecules

  • Freshwater input from melting glaciers

    • Calving of land-based ice shelves

Thermal expansion of water

• Warmer water is less dense, and therefore occupies more volume. So as temps rise, water masses will expand their volume, further contributing to sea level rise

Melting of glaciers

• Melting of glaciers adds new water to the ocean, and therefore adds to total volume and contributes to sea level rise

  • One useful distinction: melting floating sea ice isn't the major direct contributor to sea-level rise because it's already displacing water. The concern emphasized here is land-based ice entering the ocean.

Increasing storm severity as a result of climate change

• Warmer temperatures create more evaporation and precipitation

• Warmer surface ocean temps

  • Hurricanes derive strength from warmer waters so a greater potential for devastating hurricanes

• Consequences:

  • More storms

  • Stronger storms

  • Heavy rainfall