The Earth (climate) system

Week

GEOS 3410

🪑

Week Schedule

Tuesday

  1. Systems
  2. The Earth system (science)
  3. Cycles

Thursday

  1. Cycles, cont.
  2. Feedbacks

Outside of class

  • Complete/self-grade quantitative skills packet & meet with me, by Sept 12
  • Lab 1 due 11:59 pm Friday, Sept. 12

System Science

A system (in the sense of the Earth system) is a suite of interconnected reservoirs that exchange "stuff" via connections

Systems are made up of reservoirs with fluxes between them...

The reservior and fluxes are any quantity — energy, matter, etc...

Residence Time

How long does a "particle" typically remain in the reservoir?

$$\tau = \frac{m}{f}$$ This is the mean residence time for a system with constant inflow/outflow, where $\tau$ is residence time, $m$ denotes the stock, and $f$ denotes the flux.

Residence Time

A pond is in equilibrium between precipitation and evaporation. It contains 104 kg of water. Water evaporates from the pond at a rate of 10 kg/day. How long does a typical water molecule reside in the pond?
  1. 10 days
  2. 100 days
  3. 103 days
  4. 104 days

Fluxes: transfer of energy or mass

Fluxes: transfer of energy or mass

Three mechanisms

  1. Radiation (typically EM = light)
  2. Advection / convection
  3. Diffusion (mass) / conduction (energy)

Diffusion / Conduction

Random motion of particles/energy down a gradient (high→low)
Wikimedia

What happens when we increase the flux in (or decrease the flux out)?

↑ The reservoir fills ↑

What happens when we decrease the flux in (or increase the flux out)?

↓ The reservoir empties ↓

...until the reservoir reaches equilibrium with the altered fluxes.

Equilibrium & state changes

Equilibrium does not mean static

Animation credit: Keenan Crane

Equilibrium vs. non-equilibrium

State transitions

Thresholds and tipping points
UCAR

System responses in time

State transitions in time

IPCC, AR6, Fig. 1.17

🌍 Subsystems of the Earth System 🌍

  • Lithosphere (geosphere)
  • Hydrosphere
  • Cryosphere
  • Biosphere
  • Atmosphere

🌋 Lithosphere / Geosphere 🌋

🌋 Lithosphere / Geosphere 🌋

Plate tectonics are fundamental to Earth system processes

USGS

Footnote: Core → magnetosphere

Protects atmosphere from solar wind!

💧 Hydrosphere 💧

💧 Hydrosphere 💧

Oceans and climate

  • Strongly coupled with atmosphere sub-system
  • Water has high heat capacity
  • Ocean currents (both deep and shallow) transfer heat globally
NOAA

🧊 Cryosphere 🧊

(cryosphere ⊂ hydrosphere)

All the ice...

GRID-Arendal

ALL the ice...

Map of today's northern hemisphere sea ice extent
Map of today's southern hemisphere sea ice extent
National Snow and Ice Data Center

ALL THE ICE...

Snow cover January 2024

NASA Earth Observatory

Ice & climate... lots more to come in later weeks!

🦠 Biosphere 🦠

Redox chemistry

Reduction: gain an electron (e– → reduces charge)
Oxidation: lose an electron
Wikimedia

Organic & Inorganic carbon

Organic

Carbon atoms bonded directly to C and H atoms, i.e. hydrocarbons.
(sugars, fats, petroleum)

(propane)

Inorganic

Carbon atoms not bonded to C or H, often bonded to oxygen.

(calcium carbonate)

Autotrophs

Primary producers

Produce their own food by converting abiotic energy into organic compounds.

Heterotrophs

Get nutrition from organic carbon of other organisms.

Wikimedia

Biology fundamentals (for Earth scientists)

Life is made up of...

oxygen~63%
carbon~18%
hydrogen~10%
nitrogen~2%
calcium~2%
everything else~5%

Life is limited by two things: nutrients, energy

  • life gets energy from organic C (reduced) by oxidizing it (into CO2)
  • autotrophs make org-C by harnessing chemical gradients (photosynthesis, chemosynthesis)

Major life-mediated carbon transformations

Chemo-/Photosynthesis

CO2 + H2O + energy
→ CH2O + O2

formaldehyde

Respiration

C6H12O6 + 6 O2
→ 6 CO2 + 6 H2O + energy
glucose

Primary Production

  • Where is production greatest? Least?
  • Is this surprising?
Wikimedia

🌪 Atmosphere 🌪

Hydrostatic equilibrium

Outward force of atmospheric pressure balances the inward force of gravity.
Any stable atmosphere is in hydrostatic equilibrium.

Physical structure of atmosphere

\[\begin{aligned} \rho(z) &= \rho_o e^{-z/H} & P(z) &= P_o e^{-z/H} \end{aligned}\]
$H$ is the "scale height"
Table 1.5, Stull 2018

Atmospheric layers

Troposphere convective, heated at Earth's surface — clouds, wind, weather.
Stratosphere stratified, 90% of ozone
Mesosphere diminishing ozone → cooling
Thermosphere absorbs very short UV wavelengths, ionized atoms (overlaps ionosphere)

Atmospheric chemistry

Wikipedia: Atmosphere of Earth, Atmospheric Chemistry

Atmospheric chemistry

⚡light⚡ + O 2 → 2 O

Ozone (O3)

O2 + O → O3

O3 + O → 2 O2
O3 + O3 → 3 O2

Methane (CH4)

A trace greenhouse gas, until…

Complex reaction chains among H2O, CH4, & O → CO2 + H2O
CO2 is very stable in the atmosphere

Earth System Science

Foundations

Complex interconnections
NASA (1986)

Foundations

The Amsterdam Declaration (2001)

  • The Earth System behaves as a single, self-regulating system
  • Global change is real and happening now
  • Global change operates through complex, cascading effects characterized by critical thresholds and abrupt changes
  • The Earth system is currently in a no analogue state

An updated Earth system model

Steffen+ 2020

Planetary boundaries framework

Stockholm Resilience Centre

The Anthropocene epoch…

… was rejected by International Commission on Stratigraphy (ICS) and the Subcommission on Quaternary Stratigraphy (SCS). Not a strict enough definition, perhaps an event rather than an epoch.
Zhong 2024, Witze 2024

A humanist criticism of the Anthropocene

The dominant presentation of the Anthropocene ignores the role of systems, such as colonialism, capitalism and patriarchy and erases the racialised history of extractive colonialism that has given rise to this form of globalism.
McEwan 2021, "Decolonizing the Anthropocene"

Two critical research challenges facing Earth system science

  1. How stable and resilient is the Earth system?
  2. How can we better understand the dynamics of human societies?

Two very important molecules

water — H2O

carbon dioxide — CO2

Wikimedia | Wikimedia

Where's Water?

NOAA

Aqueous (water) chemistry

water = proton + hydroxide
$$ \text{H}_2\text{O} ~\longleftrightarrow ~ \text{H}^+ + \text{OH}^- $$
Excess of H+ acidic pH < 7
Excess of OH− basic pH > 7

Aqueous carbonate system

\[\begin{aligned} \text{H}_2\text{O}_{(l)} + \text{CO}~_{2~(g)}~&\longleftrightarrow~ \text{H}_2\text{O}_{(l)} + \text{CO}~_{2~(aq)} \\\\ \text{H}_2\text{O} + \text{CO}~_{2~(aq)} ~&\longleftrightarrow~ \text{H}_2\text{CO}_3 \end{aligned}\]

Aqueous carbonate system

\[\begin{aligned} \text{H}_2\text{O} + \text{CO}~_{2~(aq)} ~&\longleftrightarrow~ \text{H}_2\text{CO}_3 \\\\ \text{H}_2\text{CO}_3 ~&\longleftrightarrow~ \text{H}^{+} + \text{H}\text{CO}_3^- \\\\ \text{H}^{+} + \text{H}\text{CO}_3^- ~&\longleftrightarrow~ 2~\text{H}^{+} + \text{CO}_3^{2-} \\\\ (\text{H}_2\text{O} ~ &\longleftrightarrow ~ \text{H}^+ + \text{OH}^-) \end{aligned}\]
$$\text{Ca}^{2+} + \text{CO}_3^{2-} \longrightarrow \text{CaCO}_3$$

Aqueous carbonate system

Aqueous carbonate system

  • ↑ pH (↓ H+)… eqn. moves →
  • ↓ pH (↑ H+)… eqn. moves ←
  • ↑CO2 → ↑ H+ → ↓ pH
$$ \text{H}_2\text{O} + \text{CO}~_{2~(aq)} \leftrightarrow \text{H}_2\text{CO}_3 \leftrightarrow \text{H}^{+} + \text{H}\text{CO}_3^- \leftrightarrow 2~\text{H}^{+} + \text{CO}_3^{2-} $$

Biogeochemical Cycles

Water Cycle

Carbon Cycle

Marine carbon: the biological pump

Recycling of POC and DOC through autotrophs (phytoplankton) and heterotrophs in seawater column.
P Particulate
D Dissolved
OC Organic Carbon
IC Inorganic Carbon
← Boscolo-Galazzo+ 2018 / Wikimedia

Carbon cycle on human timescales

DOE

Inorganic carbon (carbonate-silicate) cycle

Krause 2023

The terrestrial carbon system

C transfer between surface and interior (lots of C!) on geologic timescales.
Suarez+ 2019

Nitrogen cycle

Chemistry

Transition to oxidized states by nitrification and to reduced states by denitrification.


(Anammox = Anaerobic ammonia oxidation)
Nature

Nitrogen cycle

Marine

Terrestrial

Connections?
Wikimedia, USGS

Sulfur cycle

Wikimedia

Sulfur Cycle

And short-term climate responses

Burke+ 2023, PNAS

Sulfur cycle

Sulfur in the stratosphere

Stratospheric eruptions inject sulfur into atmosphere: $$\text{SO}_2 ~\longrightarrow~ \text{H}_2\text{SO}_4$$ Sulfuric acid aerosols increase reflection of light above troposphere and cool the planet (for a few years)
Image: USGS

Feedbacks

System Interactions

Causal diagrams

Positive forcing $$ x \xrightarrow{+} y$$ As x ↑, y ↑    (As x ↓, y ↓)
Negative forcing $$ x \xrightarrow{-} y$$ As x ↑, y ↓    (As x ↓, y ↑)

Albedo (α)

The fraction of incident radiation (light) that an object reflects.

α = 1 Reflects all incident light
α =0 Absorbs all incident light
NASA Earth Observatory

Ice-albedo feedback

Permafrost-warming feedback

NPS

Silicate Weathering Feedback

Krause 2023

Lab this afternoon in MMS 273

Lab 1 due next Friday by 11:59pm

Next Week ()

  • Readings: Syllabus / Canvas
  • Complete/grade quantitative skills packet & meet with me, by Sept 12
  • Coming up: ☀️ Astrophysics of climate ☀️