Week 2: Cycles and Pertubations

Question 1

BIOGEOCHEMICAL CYCLE

Answer 1

Pathway that describes how a substance moves through the various components (i.e., spheres) of the Earth system. Critical for biological or geochemical processes of the earth systems (hydraulic cycle)
Examples
* Elements: Carbon, Nitrogen, Phosphorus, …
* Molecules: Water, silica, …
* Materials: Rock, …
* Synthetic compounds: long-lasting toxins …

Question 2

Components of a cycle:

Answer 2

Reservoirs (holding tanks)
* Oceans
* Groundwater * Ice
* Clouds
*…
Energy Sources
* Solar
* Gravity
Fluxes (how the substances move between the reservoirs)
* Evaporation
* Precipitation
* Runoff
*…

Question 3

THE EARTH SYSTEM- SPHERES AND CYCLES

Answer 3

The spheres and the cycles define the structure of the Earth system and how it responds to change

Question 4

PERTUBATIONS-EXAMPLES

Answer 4

• A landslide into a creek
• Changes of the Earth’s orbit around the sun
• Pollution of a pristine environment
• Changes to the CO2 concentration in the atmosphere
• Development of agriculture (technolog. advances)
• Changes in the economic system
   natural or human caused  environmental or social  large or small scale

Question 5

Types of system response

Answer 5

• Linear: the magnitude of the response is proportionate to the perturbation
• Non- linear: the magnitude of the response is not proportionate to the perturbation

Question 6

Response-feedback loops

Answer 6

• Feedback loops are situations where the response to a perturbation or disturbance includes an effect on the magnitude of the perturbation
  
  • Disturbance is enhanced
  • Response- positive feedback loops
    ○ Record low Arctic sea ice extent, from Sept. 16, 2012
    ○ Average minimum extent over the past 30 years (in yellow)
    ○ Include an increase in the magnitude of the perturbation
  • Response-negative feedback loop
    ○ Negative feedback is a process that occurs in a feedback loop in which the response to a small disturbance on a system include a decrease in the magnitude of the perturbation.
    ○ Not proportional to initial disturbance

Answer 7

Large spatial scales
* e.g., climate change, ice ages, …
- Small spatial scales
* e.g., construction of a dam, …
- Across spatial scales
e.g., ENSO, …

Question 8

SYSTEM RESPONSE-TEMPORAL SCALES

Answer 8

• Long time scales
  
  • e.g., ice ages, evolution, ocean circulation, …
• Short time scales
  
  • e.g., volcanic eruptions, seasonal changes in weather, …
• Across time scale
  
  • e.g., CO2 emitted today will stay in atmosphere and affect the climate system for about 100 yrs.

Question 9

SUMMARY
· The Earth system consists of spheres that interact via cycles that are composed of reservoirs, fluxes, and energy sources.
· Perturbations (disturbances) can result in complex, non-linear responses across a wide range of spatial and temporal scales.
· One of the reasons for non-linear responses are feedback loops that either amplify (positive) or reduce (negative) the magnitude of a disturbance.
· * Most global change topics that we will discuss in this course involve multiple spheres and have non-linear responses.