Y1S1 - Earth Systems Science - Hydrosphere

What is hydrology?

The cycling of continental water (solid, liquid and vapour) at all scales, and with physical, chemical and biological processes driven by that cycling

Absolute amount of water is constant (over geological timescales) - True or false?

True

List the key ways hydrological processes happen globally

·       Globally: Precipitation = Evaporation

·       Over land: Precipitation > Evaporation

·       Over oceans: Precipitation < Evaporation

·       Runoff (land -> ocean): Precipitation – Evaporation

Requirements for precipitation to occur

o   Cooling of atmosphere

o   Condensation onto nuclei

o   Growth of water/ice droplets

List out the different vegetation types

Tundra

Spruce

Deciduous woodland

Grassland

Tropical hardwood

Wheat

Larch

2 key facts about rivers

•        Drain 119 m km² of earth’s surface

•       •Contain ~1.7 x 10³ km³ water (storage)

Oceans account for 86% of water cycled - yes or no?

Yes

Oceans transport of 20-40% of global heat  (especially at lower latitudes) – They move excess energy from the equator tonorth and south pole - yes or no ?

Yes

Key features of ridges

2-4kg high

Up to 1000 Km wide

Covers 1/3 of ocean area

The two main types of plate boundaries

• Active (collision/subduction)

  • Volcanic activity

• Passive (conservative)

  • No collision or subduction

  • Transform faults (earthquakes)

Ocean cross section: Continential shelf key features

(edge of continental crust)

• Tens to hundreds of km

• Less than 150 m deep

• Coarse sediments

• Productive areas for biodiversity  (nutrients from land enter into sea, algae, decomposition)

Ocean cross section: Continential slope key features

 (connects the end of continents and start of  oceans properly)

• 1-5 km above abyssal plain

• Canyons incised (lower sea levels)

Ocean cross section: Abyssal plain key features

• Depths exceed 4000 m

• Not completely flat!

• Seamounts (volcanic)

• Atolls

What is a drifting buoy?

Measures surface temperature, wind and currents, pressure etc

Key ocean plastic facts

• Recent estimate of 3.2 MT (million tonnes) buoyant plastic in oceans & beaches (2020 data)

• Oceans receive ~0.5 MT/yr (~half from fishing)

• ~60% by weight in the surface ocean (upper 5 m)

• ~95% of oceanic plastics are >25 mm (but fragment over time & sink)

Thermohaline circulation - key features

• Transports heat, water & salts around globe

• Caused by density differences (temperature: thermo and salinity: haline)

• Conveyor belt driven by sinking in North Atlantic (& Antarctic contributes)

• Most ocean depths > 1000 m affected

• Takes ~ 500-2000 yr for full circuit (10-50 km yr^-1)

• THC links with surface current system

Gulf Stream + Thermohaline Circulation (THC) = ?

• Gulf Stream + Thermohaline Circulation (THC): Cause North Atlantic winter temps to be 15–20°C above latitudinal average

What is thermohaline circulation driven by

Driven by differences in temperature and salinity

4 major impacts of the ocean and  current:

North Atlantic Oscillation (NAO)

 El Niño-Southern Oscillation (ENSO)

 High nitrate, low chlorophyll regions (HNLC)

 Changes in the thermohaline circulation