Oceanography is important part of Geography and UPSC Preparation. Previous Year Question (PYQ) papers are invaluable resources for aspirants preparing for competitive exams like the Union Public Service Commission (UPSC) examinations. In this article we present important PYQ on Oceanography.
UPSC PYQ on Oceanography
Q- With reference to the water on the planet Earth, consider the following statements: (2021)
1. The amount of water in the rivers and lakes is more than the amount of groundwater.
2. The amount of water I n polar ice caps and glaciers is more than the amount of groundwater.
Which of the statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer- Option B
EXPLANATION
Statement 1: The majority of freshwater, with 69% stored in glaciers, 30% underground, and less than 1% in lakes, rivers, and swamps, implies that the quantity of water in rivers and lakes is less than that in groundwater.
Statement 2: It is accurate that glaciers hold 69% of freshwater, with an additional 30% stored underground. This indicates that polar ice caps and glaciers contain more water compared to groundwater.
Q- With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct? (2020)
- OMT is measured up to a depth of 26°C isotherm which is 129 meters in the southwestern Indian Ocean during January — March.
- OMT collected during January — March can be used in assessing whether the amount of rainfall in the monsoon will be less or more than a certain long-term mean.
Select the correct answer using the code given below:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer- Option B
EXPLANATION
The depth at which the 26-degree isotherm is found ranges from 50 to 100 meters, not 129 meters as stated in statement 1, therefore rendering it incorrect.
During January to March, the average depth of the 26-degree isotherm in the Southwestern Indian Ocean is recorded at 59 meters. This suggests that the statement 2 is accurate, emphasizing that Ocean Mean Temperature (OMT) serves as a more reliable indicator of monsoon rainfall compared to Sea Surface Temperature (SST) as it reflects ocean thermal energy.
Q- Consider the following statements (2018)
- Most of the world’s coral reefs are in tropical waters.
- More than one-third of the world’s coral reefs are located in the territories of Australia, Indonesia and the Philippines.
- Coral reefs host far more animal phyla than those hosted by tropical rainforests.
Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 3 only
(c) 1and 3 only
(d) 1, 2 and 3
Answer- Option D
EXPLANATION
Statement 1 is correct as most of the world’s coral reefs are indeed situated within the tropical zone between 30º N and 30º S latitude.
Regarding the conditions for coral reef growth, they thrive within a temperature range of approximately 22º to 30º C, in water depths not exceeding 200 meters, and require saline waters with an average salinity ranging from 27 to 40%. Additionally, over one-third of the world’s coral reefs are located in the territories of Australia, Indonesia, and the Philippines, confirming the accuracy of Statement 2.
Statement 3 highlights that coral reefs are predominantly found in the Pacific and Indian Oceans due to their shallow, warm, and clear waters. Moreover, coral reefs harbor a vast diversity of marine life, with some estimates suggesting that reef habitats host more than 25,000 described species from thirty-two animal phyla, surpassing even the biodiversity found in tropical rainforests. Therefore, Statement 3 is also accurate.
Q- Which of the following is/are the possible consequence/s of heavy sand mining in riverbeds? (2018)
- Decreased salinity in the river
- Pollution of groundwater
- Lowering of the water table
Select the correct answer using the code given below :
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1,2 and 3
Answer- Option B
EXPLANATION
Heavy sand mining in riverbeds accelerates the flow of water, resulting in the erosion of river banks over time. The depletion of sand aquifers in rivers contributes to the decline in the water table, negatively impacting nearby areas. Additionally, the increased turbidity at mining sites can facilitate the intrusion of saline water into coastal aquifers, contaminating groundwater and posing a risk of saltwater intrusion into freshwater sources.
Q- With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct? (2018)
- IOD phenomenon is characterised by a difference in sea surface temperature between the tropical Western Indian Ocean and the tropical Eastern Pacific Ocean.
- An IOD phenomenon can influence an El Nino’s impact on the monsoon.
Select the correct answer using the code given below:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer- Option B
EXPLANATION
The Indian Ocean Dipole (IOD) refers to the disparity in sea surface temperature between two distinct poles, namely an eastern pole situated in the eastern Indian Ocean below Indonesia, and a western pole located in the Arabian Sea (western Indian Ocean). Therefore, statement 1 is incorrect.
The IOD has a significant impact on the climate of countries bordering the Indian Ocean Basin, such as India and Australia, and plays a crucial role in influencing rainfall patterns in this region. Scientifically, the IOD is classified as a coupled ocean-atmosphere phenomenon, akin to the El Niño–Southern Oscillation (ENSO), albeit occurring in the equatorial Indian Ocean.
It is believed that the IOD is interconnected with ENSO events through the extension of the Walker Circulation westward and the associated Indonesian throughflow, which denotes the movement of warm tropical ocean water from the Pacific to the Indian Ocean. Consequently, negative IOD occurrences are often correlated with La Niña events, while positive events are linked with El Niño. Thus, statement 2 is correct.
Read UPSC PYQ on Climatology.
Q- What explains the eastward flow of the equatorial countercurrent? (2015)
(a) The Earth’s rotation on its axis
(b) Convergence of the two equatorial currents
(c) Difference in salinity of water
(d) Occurrence of the belt of calm near the equator
Answer- Option B
EXPLANATION
The equatorial countercurrents are a product of distinct surface wind patterns in tropical regions. While strong westward trade winds prevail over much of the tropical Atlantic and Pacific Oceans, weaker winds exist several hundred miles north of the equator. This imbalance causes water to pile up where winds are weaker, resulting in a surface ocean height increase of up to 6 inches (15 cm) and a deepening of the thermocline by as much as 328 feet (100 m) compared to areas further north.
The excess water flows eastward due to the Earth’s rotation, forming the equatorial countercurrents. In the Indian Ocean, this countercurrent is located several hundred miles south of the equator. Across all three oceans, the equatorial countercurrent is primarily concentrated in the upper 656 feet (200 m) above the thermocline. Its intensity varies seasonally and monthly, with the most significant changes observed in the Atlantic Ocean.
In this ocean, eastward flow peaks during the summer and fall, reaching speeds of up to 12 inches (30 cm) per second, and diminishes in the spring.
Seasonal fluctuations are less pronounced in the Pacific Ocean, where the equatorial countercurrent persists year-round, with its strongest flow occurring in the fall and winter, albeit at slightly lower speeds.
Q- Tides occur in the oceans and seas due to which among the following? (2015)
- Gravitational force of the Sun
- Gravitational force of the Moon
- Centrifugal force of the Earth
Select the correct answer using the code given below.
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- Option D
EXPLANATION
Tides refer to the regular rise and fall of sea levels caused by gravitational forces, primarily from the Moon. Thus, Statement 2 is accurate.
The Sun’s gravitational pull, along with the Earth’s centrifugal force, also contribute to tides, supporting the validity of Statements 1 and 3.
Meteorological factors like winds and atmospheric pressure changes induce surges, leading to water movement. The tide-generating force results from the disparity between the Moon’s gravitational attraction and the Earth’s centrifugal force. Tides exhibit variations in frequency, direction, and intensity across different locations and times. They are categorized based on frequency as semi-diurnal, diurnal, or mixed tides. Spring tides occur during a full moon when the Sun, Moon, and Earth align, resulting in higher tide heights. Neap tides happen when the Sun and Moon are perpendicular, causing their forces to counteract, occurring twice a month.
Also read about UPSC PYQ on Rivers in India.