My Science School

The surface ocean temperature in southern Florida soared in July 2023.    

• The surface ocean temperature in Manatee Bay, on the southern tip of Florida, hit an unprecedented 38.4°C on July 24. in what is likely a global record for the hottest seawater ever recorded.
• Meteorologists say the record is unofficial (it may be disqualified because the area is shallow, contains sea grasses and may be influenced by warm land in the nearby Everglades), but the initial reading on a buoy maintained by the Everglades National Park in Manatee Bay hit 38.4°C (101.1°F).
• National Weather Service meteorologist George Rizzuto believes the buoy is accurate, citing other nearby buoys which measured in the 36.7°C and 37.2°C (98°F and 99°F) range.
• Scientists are concerned by prolonged hot waters around Florida's coastline because they are causing coral bleaching and even in some cases deaths.
• A recent study lists a 37.6°C sea surface temperature recorded in Kuwait Bay in July 2020-likely now the former world's hottest seawater.

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With climate change wreaking havoc all across the globe, you must have come across the weather phenomena El Nino and La Nina. But have you heard of the Indian Nino? Come let's find out what it is and how it impacts the monsoon

A climate phenomenon

El Nino is a naturally occurring climate pattern associated with the abnormal warming of surface waters in the central Pacific Ocean and this will push up global temperatures and bring less-than-normal rainfall to many parts of the world, while La Nina refers to the large-scale cooling of surface temperatures in the central and eastern Pacific Ocean. With an El Nino phase now underway, the warm water spreading across the Pacific Ocean releases a large amount of heat into the atmosphere and this results in hot and dry weather conditions in many parts of the world. So what happens climatically in one place will affect weather worldwide. If there is an El Nino developing in the Pacific, it changes the winds and atmospheric circulation over the Indian Ocean.

warming it up. The Indian Ocean Dipole (1OD), which is commonly referred to as the Indian Nino, is a similar climate phenomenon playing out in the Indian Ocean, the world's third largest ocean after the Pacific and Atlantic Oceans. The Indian Ocean most of which lies in the tropical region. is bounded by Africa to the west by Asia to the north, by Australia and the islands of indonesia to the east, and by the Southern Ocean to the south. So the IOD plays out between the African coastline in the west and indonesian coastline in the east, that is between the westem and easter parts of the Indian Ocean

Phases of IOD

The IOD is an irregular shift of ocean surface temperatures in which the western Indian Ocean gets alternately wanner and colder than the eastem part. That is if the temperature of the ocean is warmer on the westem side, it is cooler on the opposite side. The Indian Ocean Dipole plays an important role in influencing weather patterns, particularly the monsoon season in India. It is known to have two main phases, positive and negative, which have their distinct impact on the monsoon.

The rainfall tends to move with the warm waters. During a positive phase, warm waters are pushed to the western part of the Indian Ocean resulting in greater-than-average surface sea temperatures and a greater-than-normal rainfall, while cold waters from the deep are brought to the surface in the eastern Indian Ocean. In other words, a positive IOD means a wetter west and a drier east. The IOD is said to be negative when the western Indian Ocean gets cooler. This fluctuation in temperatures leads to changes in atmospheric circulation patterns, affecting the monsoon.

A positive phase of the IOD enhances the monsoon flow to India and causes floods in African countries, while it reduces rainfall and causes drier conditions and droughts in Indonesia and Australia. This pattern gets reversed during the negative phase. According to the India Meteorological Department (IMD). there is a higher probability for positive IOD conditions this year and this could potentially limit the impact of El Nino on the subcontinent.

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High temperatures and heatwaves across the globe saw records broken in July 2023 on land and in the oceans. The oceans serve as the Earth's heat reservoir, absorbing substantial amounts of thermal energy as a result of their continuous interaction with the atmosphere. Under specific conditions. prolonged periods of unusually high temperatures in the oceans are called marine heatwaves. much like their atmospheric counterparts.

These higher temperatures could be driven by increased heat input from the atmosphere. decreased heat losses from the ocean or the transfer of warmer water masses through currents Over the past two decades these events have become more prevalent and widespread, having been observed in various areas of the global ocean, in both regional and large scales, at the surface of the ocean and at depth

In particular, recent data shows the occurrence of marine heatwaves surged by 34 percent between 1925 and 2016. While the exact mechanisms triggering marine heatwaves vary from region to region. there are two primary factors. In some instances, the atmospheric conditions themselves play a pivotal role. During such episodes. stagnant air masses and prolonged high temperatures in the atmosphere conspire to heat the ocean's surface. setting the stage for a marine heatwave event. This pattern was notably evident during a 2012 North Atlantic event, which saw one of the highest sea surface temperatures ever recorded.

In other cases, the main driver is the movement of ocean currents, which transport relatively warm water masses to new areas. When these warm masses converge in specific regions, they cause a rapid and abrupt increase in the sea's surface temperature. This was witnessed in the 2015 Tasman Sea (situated between Australia and New Zealand) event.

As the impacts of marine heatwaves reverberate across the globe, understanding the complex interplay between the oceans and the atmosphere is crucial for predicting the Occurrence of these extreme events. In the face of climate change, conserving and protecting our oceans becomes ever more critical. Therefore improving marine heatwave predictability is crucial to empower communities and ecosystems alike to adapt and build resilience. By better understanding the science behind marine heatwaves and taking collective action, people can work towards a more resilient and sustainable future for the oceans. (With inputs from agencies)

Picture Credit: Google