TF阅读真题第871篇Carbon Dioxide Levels in the Ocean

题目：

Carbon Dioxide Levels in the Ocean

The concentration of carbon dioxide gas (CO2) is rising in the atmosphere, and some of this CO2 is taken up by ocean surface waters. To determine how much CO2 has ended up in the ocean, oceanographers have made measurements at nearly ten thousand sites. The results show that carbon content has increased everywhere in the ocean. These results contradict the claim that the atmospheric increase in CO2 is a result of CO2 being released by the ocean, similar to what happened at the end of the ice ages (long periods of reduction in the temperature of Earth’s surface and atmosphere). The carbon added to the climate system from fossil fuels has increased CO2 levels in both the atmosphere and the ocean.

The fact that the ocean has taken up so much carbon from the atmosphere sounds like a blessing. If this were not the case, atmospheric CO2 concentration would already be much higher and climate would have warmed more. But scientists are now realizing that this ocean CO2 uptake is in itself a huge problem: it makes the ocean waters more acidic. This is very simple chemistry-CO2 dissolved in water makes carbonic acid. The effect can easily be calculated, and long-term measurement stations are showing it directly. Acidity is measured in units called pH-the lower the pH value, the more acidic the water is. Since preindustrial times, the pH value of the ocean surface has already dropped by 0.1 units. This corresponds to a 30 percent increase in the number of the chemically aggressive hydrogen ions (electrically charged particles) in the water.

The reason excessive acidity is very important is its effect on marine life. Many marine organisms build hard shells that are made of calcium carbonate (CaCO3), which comes in two forms: calcite and aragonite. Familiar sea shells are made from CaCO3, but more importantly so are the shells of the main microscopic plankton species that form the basis of the marine food web. And coral reefs, which host the most beautiful and diverse marine ecosystems, are also built from calcium carbonate. This marine life can thrive only when there is an overabundance of calcium carbonate in seawater. Put more technically, calcium carbonate needs to be supersaturated, so that these organisms can extract it from the water to incorporate it into their shells. There is a well-defined chemical threshold where calcium carbonate switches from being supersaturated to undersaturated and by adding CO2 and making seawater more acidic, we are pushing the ocean toward that threshold.

In fact, this threshold can be seen for real in the ocean: while the surface waters are supersaturated, the deep waters are undersaturated in calcium carbonate for natural reasons. The dividing line (called the saturation horizon) is at different depths depending on location, varying between 200 meters depth in high latitudes and 3,500 meters depth in parts of the Atlantic. What happens to the shells of dead plankton that sink down below the saturation horizon? They dissolve, as undersaturated water is corrosive to these shells. That’s why the saturation horizon is often compared to the snow line in the mountains, with the snowflakes being the microscopic shells constantly drifting down from the biologically productive surface waters. Where the ocean bottom is above this line, the shells remain intact and form white sediments that are analyzed by scientists to give information about past climates. The white chalk cliffs of Dover, England, are made from this type of calcareous sediment that was uplifted above the sea surface.

Measurements show that this saturation horizon is moving upward in the water column, consistent with the uptake of anthropogenic (human caused) CO2 by the ocean. This raises concerns for marine life-particularly in the Southern Ocean, where the saturation horizon is already very shallow at only 200 meters depth. Laboratory experiments where plankton were grown in water enriched with CO2 show that their growth is impaired. According to model simulations, by the year 2050 the changes in ocean chemistry will start to harm marine life if the atmospheric CO2 concentration continues to rise. For coral reefs, the IPCC (Intergovernmental Panel on Climate Change) report concludes that the impacts of acidification may be severe-corals produce aragonite, the form of calcium carbonate that is more susceptible to acidification.

 

 

1

The concentration of carbon dioxide gas (CO2) is rising in the atmosphere, and some of this CO2 is taken up by ocean surface waters. To determine how much CO2 has ended up in the ocean, oceanographers have made measurements at nearly ten thousand sites. The results show that carbon content has increased everywhere in the ocean. These results contradict the claim that the atmospheric increase in CO2 is a result of CO2 being released by the ocean, similar to what happened at the end of the ice ages (long periods of reduction in the temperature of Earth’s surface and atmosphere). The carbon added to the climate system from fossil fuels has increased CO2 levels in both the atmosphere and the ocean.

Paragraph 1 supports which TWO of the following statements about oceanic CO2 levels? To receive credit, you must select TWO answer choices.

Factual Information Questions事实信息题

Select 2 answers

AAll areas of the ocean have experienced an increase in CO2 in modern times.

BThe amount of CO2 being released by the ocean is increasing.

CThe rise in oceanic CO2 has been caused by fossil fuels.

DOceanic CO2 has increased more rapidly in recent years than it did at the end of the ice ages.

 

2

The concentration of carbon dioxide gas (CO2) is rising in the atmosphere, and some of this CO2 is taken up by ocean surface waters. To determine how much CO2 has ended up in the ocean, oceanographers have made measurements at nearly ten thousand sites. The results show that carbon content has increased everywhere in the ocean. These results contradict the claim that the atmospheric increase in CO2 is a result of CO2 being released by the ocean, similar to what happened at the end of the ice ages (long periods of reduction in the temperature of Earth’s surface and atmosphere). The carbon added to the climate system from fossil fuels has increased CO2 levels in both the atmosphere and the ocean.

The fact that the ocean has taken up so much carbon from the atmosphere sounds like a blessing. If this were not the case, atmospheric CO2 concentration would already be much higher and climate would have warmed more. But scientists are now realizing that this ocean CO2 uptake is in itself a huge problem: it makes the ocean waters more acidic. This is very simple chemistry-CO2 dissolved in water makes carbonic acid. The effect can easily be calculated, and long-term measurement stations are showing it directly. Acidity is measured in units called pH-the lower the pH value, the more acidic the water is. Since preindustrial times, the pH value of the ocean surface has already dropped by 0.1 units. This corresponds to a 30 percent increase in the number of the chemically aggressive hydrogen ions (electrically charged particles) in the water.

Which of the following best describes the relationship between paragraph 2 and paragraph 1 ？

Organization Questions组织结构题

AParagraph 2 explains how awareness of increased atmospheric warming led oceanographers to make the measurements described in paragraph 1.

BParagraph 2 explains why the gas-exchange process identified in paragraph 1， though immediately beneficial, creates a serious difficulty.

CParagraph 2 argues that it is no longer chemically possible for the ocean to release CO2 as it had done, as paragraph 1 notes, at the end of the ice ages.

DParagraph 2 describes some negative effects of having the amount of oceanic CO2 rise faster than the amount of atmospheric CO2 discussed in paragraph 1.

 

3

The fact that the ocean has taken up so much carbon from the atmosphere sounds like a blessing. If this were not the case, atmospheric CO2 concentration would already be much higher and climate would have warmed more. But scientists are now realizing that this ocean CO2 uptake is in itself a huge problem: it makes the ocean waters more acidic. This is very simple chemistry-CO2 dissolved in water makes carbonic acid. The effect can easily be calculated, and long-term measurement stations are showing it directly. Acidity is measured in units called pH-the lower the pH value, the more acidic the water is. Since preindustrial times, the pH value of the ocean surface has already dropped by 0.1 units. This corresponds to a 30 percent increase in the number of the chemically aggressive hydrogen ions (electrically charged particles) in the water.

According to paragraph 2， long-term measurement stations have provided evidence of all of the following changes in ocean water since preindustrial times EXCEPT

Negative Factual Information Questions否定事实信息题

Aan increase in the amount of CO2 dissolved in ocean water

Ban increase in the acidity of ocean water

Can increase in the pH unit measurement of ocean water

Dan increase in the number of chemically aggressive hydrogenions in ocean water

 

4

The reason excessive acidity is very important is its effect on marine life. Many marine organisms build hard shells that are made of calcium carbonate (CaCO3), which comes in two forms: calcite and aragonite. Familiar sea shells are made from CaCO3, but more importantly so are the shells of the main microscopic plankton species that form the basis of the marine food web. And coral reefs, which host the most beautiful and diverse marine ecosystems, are also built from calcium carbonate. This marine life can thrive only when there is an overabundance of calcium carbonate in seawater. Put more technically, calcium carbonate needs to be supersaturated, so that these organisms can extract it from the water to incorporate it into their shells. There is a well-defined chemical threshold where calcium carbonate switches from being supersaturated to undersaturated and by adding CO2 and making seawater more acidic, we are pushing the ocean toward that threshold.

According to paragraph 3， excessive ocean acidity is problematic in part because such acidity

Factual Information Questions事实信息题

Aincreases the amount of CO2 in ocean water

Bcauses the marine food web to depend more on calcium carbonate than plankton

Cmakes it impossible for organisms to absorb a chemical needed to form a hard body covering

Dchanges the threshold at which calcium carbonate becomes calcite and aragonite

5

In fact, this threshold can be seen for real in the ocean: while the surface waters are supersaturated, the deep waters are undersaturated in calcium carbonate for natural reasons. The dividing line (called the saturation horizon) is at different depths depending on location, varying between 200 meters depth in high latitudes and 3,500 meters depth in parts of the Atlantic. What happens to the shells of dead plankton that sink down below the saturation horizon? They dissolve, as undersaturated water is corrosive to these shells. That’s why the saturation horizon is often compared to the snow line in the mountains, with the snowflakes being the microscopic shells constantly drifting down from the biologically productive surface waters. Where the ocean bottom is above this line, the shells remain intact and form white sediments that are analyzed by scientists to give information about past climates. The white chalk cliffs of Dover, England, are made from this type of calcareous sediment that was uplifted above the sea surface.

The word “intact”in the passage is closest in meaning to

Vocabulary Questions词汇题

Avisible

Bhard

Cwhole

Dthick

 

6

In fact, this threshold can be seen for real in the ocean: while the surface waters are supersaturated, the deep waters are undersaturated in calcium carbonate for natural reasons. The dividing line (called the saturation horizon) is at different depths depending on location, varying between 200 meters depth in high latitudes and 3,500 meters depth in parts of the Atlantic. What happens to the shells of dead plankton that sink down below the saturation horizon? They dissolve, as undersaturated water is corrosive to these shells. That’s why the saturation horizon is often compared to the snow line in the mountains, with the snowflakes being the microscopic shells constantly drifting down from the biologically productive surface waters. Where the ocean bottom is above this line, the shells remain intact and form white sediments that are analyzed by scientists to give information about past climates. The white chalk cliffs of Dover, England, are made from this type of calcareous sediment that was uplifted above the sea surface.

According to paragraph 4， which TWO of the following statements are true of the saturation horizon? To receive credit, you must select TWO answer choices.

Factual Information Questions事实信息题

Select 2 answers

AIt is the location in ocean water where calcium carbonate switches from being supersaturated to being undersaturated.

BIt is located above the ocean bottom even in shallow waters.

CIt is usually located in ocean depths of more than 3,500 meters.

DIt occurs at different depths depending on the latitude.

 

7

The fact that the ocean has taken up so much carbon from the atmosphere sounds like a blessing. If this were not the case, atmospheric CO2 concentration would already be much higher and climate would have warmed more. But scientists are now realizing that this ocean CO2 uptake is in itself a huge problem: it makes the ocean waters more acidic. This is very simple chemistry-CO2 dissolved in water makes carbonic acid. The effect can easily be calculated, and long-term measurement stations are showing it directly. Acidity is measured in units called pH-the lower the pH value, the more acidic the water is. Since preindustrial times, the pH value of the ocean surface has already dropped by 0.1 units. This corresponds to a 30 percent increase in the number of the chemically aggressive hydrogen ions (electrically charged particles) in the water.

Which of the following can be inferred from paragraph 4 about the white chalk cliffs of Dover, England?

Inference Questions推理题

AThey were formed in waters that were above the saturation horizon.

BThey provide an accurate record of changes in atmospheric CO2 over time.

CThey are made up of sediment that contains very few shells.

DThey were part of an area of the ocean that was undersaturated in calcium carbonate.

 

8

Measurements show that this saturation horizon is moving upward in the water column, consistent with the uptake of anthropogenic (human caused) CO2 by the ocean. This raises concerns for marine life-particularly in the Southern Ocean, where the saturation horizon is already very shallow at only 200 meters depth. Laboratory experiments where plankton were grown in water enriched with CO2 show that their growth is impaired. According to model simulations, by the year 2050 the changes in ocean chemistry will start to harm marine life if the atmospheric CO2 concentration continues to rise. For coral reefs, the IPCC (Intergovernmental Panel on Climate Change) report concludes that the impacts of acidification may be severe-corals produce aragonite, the form of calcium carbonate that is more susceptible to acidification.

Paragraph 5 supports which of the following statements about how marine organisms will be affected if oceanic CO2 levels keep rising?

Factual Information Questions事实信息题

AMarine life in the northern parts of the ocean will be more severely affected than marine life in the Southern Ocean.

BMarine plankton will be more severely affected than other types of marine organisms will be.

CMarine life in areas with a shallow saturation horizon will be less affected than marine life in areas with a deep saturation horizon.

DMarine life that contains aragonite will be affected more severely than marine life that contains another form of calcium carbonate.

 

9

Measurements show that this saturation horizon is moving upward in the water column, consistent with the uptake of anthropogenic (human caused) CO2 by the ocean. [■]This raises concerns for marine life-particularly in the Southern Ocean, where the saturation horizon is already very shallow at only 200 meters depth.[■]Laboratory experiments where plankton were grown in water enriched with CO2 show that their growth is impaired. [■]According to model simulations, by the year 2050 the changes in ocean chemistry will start to harm marine life if the atmospheric CO2 concentration continues to rise. [■]For coral reefs, the IPCC (Intergovernmental Panel on Climate Change) report concludes that the impacts of acidification may be severe-corals produce aragonite, the form of calcium carbonate that is more susceptible to acidification.

Look at the four squaresthat indicate where the following sentence could be added to the passage

It may not be too long before this effect on marine organisms is observed in nature.

Insert Text Questions句子插入题

Where would the sentence best fit？Click on a square  sentence to the passage.

10

Some of the CO2 in the atmosphere is being taken up by ocean surface waters.

Prose Summary Questions概要小结题

Select 3 answers

AThe absorption of CO2 by ocean surface waters has slowed climate warming, but this has created changes in water conditions that make it difficult for some marine organisms to thrive.

BSince it became easy to measure the acidity of ocean waters, scientists have demonstrated how ch more acidic ocean waters have to be before marine life is severely affected.

CAs the rise in atmospheric CO2 concentration continues, the corresponding uptake by the ocean has important consequences for marine life, especially from greater acidification.

DMeasurements of CO2 levels at numerous ocean sites have revealed that the increase in carbon in the ocean has had the same effect on the climate system as happened at the end of the ice ages.

EIncreased uptake of CO2 by the ocean is changing the structure of the water column in ways that the supply of calcium carbonate for the growth of some marine organisms is under threat.

FThe similarity of the saturation horizon in the ocean to the snow line in the mountains helps scientists explain how the absorption of human-caused CO2 by the ocean affects different marine organisms.