Marine Heat Waves

19 Feb 2024 Marine Heat Waves

This article covers ‘Daily Current Affairs’ and the topic details of ”Arctic Marine Heat Waves”.This topic is relevant in the “Environment” section of the UPSC CSE exam.

Why in the News? 

A new study published in the journal Nature Communications, titled ‘Arctic marine heatwaves forced by greenhouse gases and triggered by abrupt sea-ice melt’, demonstrates that unprecedented Marine Heat Waves (MHW) episodes have occurred throughout the Arctic Ocean since 2007.

Key findings of the study

Characteristics of Arctic Marine Heat Waves (MHWs):

Between 2007 and 2021, the Arctic experienced 11 MHW events, marked by extended periods of elevated Sea Surface Temperatures (SST). These occurrences coincided with notable declines in Arctic Sea ice. The State of the Global Climate 2022 report highlighted severe and extreme marine heat waves in the Laptev and Beaufort seas from spring to autumn in 2022.

Long-Term Trends:

A distinct long-term warming trend is evident in the Arctic, with SST increasing at a rate of 1.2°C per decade from 1996 to 2021. The eastern Arctic marginal seas have witnessed a rise in the frequency of extreme SST events over the past two decades.

Reduction in Ice Cover:

The perpetual sea ice cover in the Arctic, known for reflecting solar radiation, has significantly diminished since the mid-1990s, both during summer and winter. A noticeable shift occurred since 2007 from a thicker and irregular ice cover to a thinner and more uniform one. This thinner ice is less resilient, leading to quicker melting and allowing incoming solar radiation to warm the water’s surface.

Impact of Greenhouse Gas (GHG):

Marine heatwaves exceeding 1.5°C would not occur without GHGs. GHGs serve as a significant cause for moderate marine heatwaves, with a probability ranging from 66-99%.

Drivers Behind Arctic MHWs:

Arctic MHWs primarily manifest over marginal seas, including the Kara, Laptev, East Siberian, and Chukchi seas. These areas are characterised by shallow mixed-layer depths and predominantly first-year ice cover, conditions conducive to MHW development. First-year ice refers to sea ice formed in a single winter season, typically melting away entirely in the following summer melt season. The potential for abrupt sea ice retreat raises concerns as it could trigger marine heatwave events.

Concerns and Consequences:

The study issues a stark warning about the potential dramatic consequences of marine heatwaves, impacting food chains, fish stocks, and overall biodiversity.

Study Technique:

The study uses the Extreme Event Attribution (EEA) technique to assess the effect of GHG forcing in Arctic MHWs. This method discerns the extent to which human-induced climate change influences the likelihood and severity of specific extreme weather events.

About Marine Heat Waves

Marine Heat Waves, as per the IPCC Sixth Assessment Report, are characterised as periods when water temperature deviates significantly from historical temperatures for the given time of the year. This abnormal warmth persists for days to months. MHW occurs when the sea surface temperature rises 3 or 4 degrees Celsius above the average temperature for a minimum of 5 consecutive days. This phenomenon can occur in any oceanic location and can extend over scales of up to thousands of kilometres.

Natural and Anthropogenic Causes of Marine Heat Waves (MHWs)

• Climate Change:

1. Greenhouse Gas Emissions: Increased levels of greenhouse gases, such as carbon dioxide, contribute to the greenhouse effect, trapping heat in the atmosphere and elevating sea surface temperatures.
2. Global Warming: The overall rise in global temperatures amplifies heat waves, affecting oceanic regions and giving rise to MHWs.

• Atmospheric Conditions:

1. Persistent High-Pressure Systems: Stagnant high-pressure systems can lead to prolonged periods of calm weather, allowing the sun to intensify its heat on the ocean surface.
2. Weakening Winds: Reduced wind speeds impede the ocean’s ability to cool down, promoting the accumulation of heat.

• Ocean Currents and Circulation:

1. Ocean Current Anomalies: Changes in ocean currents, driven by natural variability or climate change, can create pockets of warmer water or impede the natural cooling process.
2. Stalled Circulation Patterns: Disruptions in typical ocean circulation patterns can result in the entrapment of warm water, fostering MHWs.

• Underwater Heatwaves:

1. Underwater Geothermal Activity: Submarine volcanic activity and geothermal vents release heat into the ocean, creating localised warm zones.
2. Deep Ocean Processes: Natural processes deep within the ocean can influence temperature variations, contributing to the onset of MHWs.

• El Niño and La Niña Events:

1. El Niño: The periodic warming of central and eastern Pacific waters during El Niño events can have cascading effects on global weather patterns, leading to MHWs.
2. La Niña: Conversely, La Niña events, characterised by cooler-than-average sea surface temperatures, can influence MHW occurrence in different ways.

• Feedback Loops:

1. Ice-Albedo Feedback: Melting ice reduces the Earth’s albedo, allowing more sunlight to be absorbed by the ocean, further increasing temperatures.
2. Positive Feedback Mechanisms: Interactions between warming ocean waters, atmospheric conditions, and other factors create self-reinforcing loops, sustaining MHWs.

Impact of Marine Heat Waves (MHWs):

• Ecosystem Disruption: MHWs disrupt marine ecosystems, causing species distribution and composition shifts. Sensitive species, including corals and kelps, face bleaching and mortality.
• Fisheries and Aquaculture: MHWs lead to altered fish migration patterns, affecting commercial and subsistence fisheries. Aquaculture operations face economic losses due to adverse conditions.
• Biodiversity Loss: Increased stress on marine life leads to biodiversity loss, impacting overall ecosystem health. Vulnerable species face heightened extinction risks.
• Coral Reefs: Coral bleaching occurs as elevated temperatures force symbiotic algae to leave coral tissues. Prolonged MHWs result in coral mortality and degradation of reef ecosystems.
• Economic Ramifications: Fisheries, tourism, and coastal economies suffer as MHWs disrupt traditional livelihoods. Losses in revenue and employment opportunities exacerbate economic vulnerabilities.
• Extreme Weather Events: Intensified storms and hurricanes result from warmer ocean temperatures associated with MHWs. Increased risk of destructive weather events poses threats to coastal communities.

Download Yojna daily current affairs eng med 19th feb 2024

Prelims practice question

Q1. Which of the following statements is/are correct about the ‘methane hydrate’ deposits? (UPSC Prelims-2019)

1. Global warming might trigger the release of methane gas from these deposits.
2. Large ‘methane hydrate deposits are found in the  Arctic Tundra and under the sea floor.
3. Methane in the atmosphere oxidises to carbon dioxide after a decade or two.

Select the correct answer using the code given below.

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

ANSWER: (d)

Mains practice questions 

Q1. What role do marine heat waves play in disrupting coastal tourism, and what strategies can be employed to manage and promote resilient tourism practices in affected regions sustainably?

Q2. In what ways do marine heat waves contribute to the increased intensity of extreme weather phenomena, and how can communities prepare for and adapt to the heightened risks associated with these events?

Himanshu Mishra

I am a content developer and have done my Post Graduation in Political Science. I have given 2 UPSC mains, 1 IB ACIO interview and have cleared UGC NET JRF too.