Earth's five systems and how they affect each other

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Card

   Permafrost holds about 1,500 Gt of carbon (billion tonnes). The air holds about 900 Gt of carbon. Loop: warming thaws ground, microbes release carbon gas, the gas adds warming.

2. 1.

   Noah traces the loop. If 5% of the permafrost carbon is released, what share of the air's carbon is that, and what sign is the loop?

   • A positive loop; 75 Gt is about 83% of the air's carbon, nearly the whole of it
   • A negative loop; 75 Gt is about 8% of the air's carbon, since the gas cools the air
   • A positive loop; 75 Gt is about 0.8% of the air's carbon, a trace of it
   • A positive loop; 75 Gt is about 8% of the air's carbon

3. Three loops (+ adds to the change, - reverses it)

   Loop	Links
   A	warmer air + more evaporation + more water vapor + warmer air
   B	warmer air + more weathering - less CO2 in the air + warmer air
   C	warmer air + more thaw + more carbon gas + warmer air

4. 2.

   Bo counts the reversing links in each loop. Which loops amplify a change?

   • A just amplifies, since water vapor is the one gas that traps heat
   • A, B and C amplify, since each loop returns to warmer air
   • A and C amplify; B damps, since it has one reversing link
   • B and C amplify, since each loop crosses three systems

5. Card

   Trees supply 30% of a region's rain by releasing water vapor (example data). Loop: less rain removes trees, fewer trees release less vapor, and less rain falls.

6. 3.

   A drought removes 20% of the forest. Luz assumes vapor falls in step. By what percent does rain fall, and what sign is the loop?

   • Rain falls 20%; the loop is positive, since less rain removes more trees
   • Rain falls 6%; the loop is positive, since less rain removes more trees
   • Rain falls 30%; the loop is positive, since less rain removes more trees
   • Rain falls 6%; the loop is negative, since fewer trees need less rain

7. Summer sea ice and ocean warmth (example data)

   Year	Sea ice (million km2)	Ocean warming (degrees C)
   2000	6.3	0.2
   2010	4.9	0.5
   2020	3.7	0.8

8. 4.

   Jun judges four claims about the table. Which claim does it support best?

   • Ice fell 2.6 million km2 as the ocean warmed 0.6 degrees C, which fits an ice-albedo loop but does not prove it
   • The table proves that ice loss caused all of the warming and nothing else did
   • The table proves that warming caused all of the ice loss and nothing else did
   • Ice and temperature moved in opposite years, so the two systems are unrelated

9. A bay over 30 years (example data)

   Year	Nitrate load (thousand tonnes)	Lowest bottom oxygen (mg/L)
   1990	20	4.0
   2000	30	2.5
   2010	45	1.2
   2020	30	2.0

10. 5.

    Kira judges claims about the table. Which claim does it support best?

    • Cutting the load restored oxygen fully, back to its level in 1990
    • Oxygen fell as nitrate rose, then partly recovered: a link, not proof of one cause
    • Low oxygen drove the nitrate load up, since the two moved together
    • The table shows that nitrate alone caused the low oxygen in this bay over 30 years

11. Global sea level rise since 1993 (example data shaped like satellite records)

    Year	Rise since 1993 (mm)
    1993	0
    2003	32
    2013	66
    2023	101

12. 6.

    Pia grades claims about the table. Which reply fits it, and what can the table not tell?

    • The rise sped up slightly (32, 34, then 35 mm a decade); ice melt cannot be split from warmer water
    • The rise held steady at 32 mm a decade, and the table shows that ice melt alone caused it, with no other cause
    • The rise slowed after 2003, since 66 mm is under twice the first decade
    • Sea level is a hydrosphere change, so ice and air play no part in it

13. Card

    Nitrate travels 2,000 km down a river at 0.5 m/s to a bay. The bay forms warm, layered water in early June.

14. 7.

    Fertilizer washes into the river on April 15. When does Tala expect the nitrate to reach the bay, and why does it matter?

    • About July 2 of the next year, after the bay layers and mixes again
    • About April 20, so the nitrate reaches the bay well before the bay layers
    • About June 1, just as warm, layered water starts to trap low oxygen
    • About June 1, but the nitrate stays on the farm and does not reach the bay
15. 8.

    About 27.7 million tons of Saharan dust reach the Amazon each year, with 22,000 tons of phosphorus. What share is phosphorus, and does it matter, by Zee?

    • About 0.8%, small but about what the forest loses to rain and floods each year
    • About 8%, a large share that more than doubles the forest's phosphorus
    • About 0.08%, small but about what the forest loses to rain and floods each year
    • About 0.08%, too small to matter to living things in the forest
16. 9.

    A, farmland around it, 80, 45, 0.8; B, forest around it, 10, 4, 7.5. Milo compares the lakes. Which interaction explains lake A's low oxygen?

    • Algae release oxygen, so lake A's 45 chlorophyll should raise its bottom oxygen
    • Runoff phosphorus feeds algae, about 11 times the chlorophyll, and their decay uses up bottom oxygen
    • Lake B has less algae because it is deeper, as the table shows
    • Low bottom oxygen made the algae grow, so the algae came second

17. How fast each feedback responds (approximate)

    Feedback	Time to respond
    Sea ice and snow	years to decades
    Permafrost carbon	decades to centuries
    Rock weathering	about 100,000 years

18. 10.

    Esme asks if rock weathering could cancel warming within 100 years. Which reply is best?

    • Yes: weathering is a negative loop, so it cancels warming at any speed
    • No: weathering responds over about 100,000 years, about 1,000 times slower than 100 years
    • No: weathering acts on rocks, so it cannot change the air
    • No: weathering responds about 100 times slower than 100 years