Consider the following statements regarding Marine Heatwaves (MHWs):
1. Marine heat waves occur when sea surface temperatures rise by 1–2°C above the average for at least five consecutive days.
2. According to the International Union for Conservation of Nature (IUCN), the frequency of MHWs has increased by 50% over the past decade.
3. Nearly 90% of the excess heat from global warming is absorbed by the oceans, contributing to the intensification of MHWs.
4. MHWs can cause large-scale destruction of kelp forests and disrupt marine ecosystems.

Which of the statements given above are correct?
(a) 1, 2, and 3 only
(b) 2, 3, and 4 only
(c) 1, 3, and 4 only
(d) 1, 2, 3, and 4

Question

Consider the following statements regarding Marine Heatwaves (MHWs):
1. Marine heat waves occur when sea surface temperatures rise by 1&ndash;2&deg;C above the average for at least five consecutive days.
2. According to the International Union for Conservation of Nature (IUCN), the frequency of MHWs has increased by 50% over the past decade.
3. Nearly 90% of the excess heat from global warming is absorbed by the oceans, contributing to the intensification of MHWs.
4. MHWs can cause large-scale destruction of kelp forests and disrupt marine ecosystems.

Which of the statements given above are correct?
(a) 1, 2, and 3 only
(b) 2, 3, and 4 only
(c) 1, 3, and 4 only
(d) 1, 2, 3, and 4

ONLiNE UPSC · Accepted Answer

Statement 1 is not correct: A marine heatwave occurs when the sea surface temperature (SST) rises to 3 or 4 degree celsius above the average SST for at least 5 consecutive days. 1-2&deg;C rise in Sea Surface Temperature generally does not lead to the formation of Marine Heatwaves.

Statement 2 is correct: A 2021 report by the IUCN said MHWs had increased by 50% over the past decade attributed to global warming.

Statement 3 is correct: The primary reason for intensified MHWs is global warming. As global temperature has increased more than 1.5 degrees Celsius higher than pre-industrial levels (1850-1900 period), 90% of extra heat is absorbed by the oceans. All this leads to an increase in average sea surface temperature.

Statement 4 is correct: One of the most significant impacts of MHWs is the occurrence of fish kills, where large numbers of fish die suddenly due to elevated sea temperatures. Beyond fish kills, marine heatwaves are also responsible for the destruction of kelp forests. Another major impact of MHWs is coral bleaching. In 2024, Australia&rsquo;s Great Barrier Reef experienced its 7th mass coral bleaching event, the result of repeated marine heatwaves.

Min. Time: 3 S Max Time: 3 S
M Question 1	⏱ 0
Consider the following statements regarding Marine Heatwaves (MHWs): 1. Marine heat waves occur when sea surface temperatures rise by 1–2°C above the average for at least five consecutive days. 2. According to the International Union for Conservation of Nature (IUCN), the frequency of MHWs has increased by 50% over the past decade. 3. Nearly 90% of the excess heat from global warming is absorbed by the oceans, contributing to the intensification of MHWs. 4. MHWs can cause large-scale destruction of kelp forests and disrupt marine ecosystems. Which of the statements given above are correct? (a) 1, 2, and 3 only (b) 2, 3, and 4 only (c) 1, 3, and 4 only (d) 1, 2, 3, and 4

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