Carbon Cycling & Earth-System Feedbacks — Practice · Grade 9 Science

Chapter: Oceans, Carbon & Climate

What this practice covers

By the end of Carbon Cycling & Earth-System Feedbacks you should be able to:

8 questions, numeric, multiple choice and written answer, each with a worked explanation.

Vocabulary used: reservoir, flux, feedback.

Problem 1

Inputs are 15 carbon units/year and outputs are 11. Find storage change.
Answer and explanation

4 carbon units/year

15 − 11 = 4.

Problem 2

An amplifying feedback…
  1. opposes every change
  2. increases the effect of an initial change
  3. is always good
  4. contains no causal links
Answer and explanation

increases the effect of an initial change

It reinforces the initial change.

Problem 3

Distinguish a carbon reservoir from a flux.
Answer and explanation

A reservoir is an amount stored; a flux is a transfer rate per time.

Problem 4

Warming reduces ice cover; darker surfaces absorb more sunlight. Identify the feedback and mechanism. Explain the reasoning in your own words.
Answer and explanation

A positive feedback through changing albedo.

Initial warming reduces reflective ice.

More absorption can reinforce the initial warming.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 5

A reservoir gains 8 units/year and loses 5. Find net annual change. Show the reasoning, not just the conclusion.
Hints

Positive refers to amplification, not a beneficial effect.

Answer and explanation

+3 units/year, assuming these are its only flows.

Problem 6

Give a condition needed before calling an observed link a feedback.
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

The response must loop back to influence the original change; correlation alone does not establish that causal loop.

Problem 7

Acidification describes a pH decrease, not necessarily pH below sevenAcidification describes a pH decrease, not necessarily pH below sevenSupplied pH7.888.20123Relative dissolved-CO₂ addition (model index)A fall in pH is acidification even when pH remains above 7.
Original qualitative supplied pH trend against a model addition index. It is not an observed seawater titration or a calibrated CO₂-to-pH relationship. The graph illustrates terminology and avoids implying a universal linear ocean-chemistry response.
Interpret the supplied visual model. Can a change from pH 8.2 to 8.0 be described as acidification while the water remains above pH 7?
Answer and explanation

Yes. The pH decreased. Acidification concerns that change, while above/below seven is a separate reference comparison under relevant conditions.

Compare the starting and ending pH while noting that every value shown remains above seven. The horizontal index is deliberately not a measured concentration.

Yes. The pH decreased. Acidification concerns that change, while above/below seven is a separate reference comparison under relevant conditions.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 8

A model store begins at 80 carbon units. Annual input is 6 and net uptake is 4 for five years. Find final storage. Would cutting input to 5 reverse the trend if uptake remains 4?
Answer and explanation

It gains 2 units/year, or 10 in five years, ending at 90. Cutting input to 5 gives +1 unit/year, so the store still rises more slowly; it does not decline under those assumptions.

Compute net 6−4 = 2 units/year.

Multiply by five and add to 80 to get 90.

Recalculate 5−4 = +1 and distinguish a smaller increase from a decline.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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