Meet Chinglen Tensubam from Manipur, India, whose innovative research is bound to make a significant impact in Indo-Australian scientific collaboration. With a PhD in Ocean Engineering from the University of Melbourne and an MTech in Earth System Science and Technology from IIT Kharagpur, Tensubam is diving deep into the mysteries of our oceans.
His research unravels how ocean surface waves dance with marine ecosystems and influence phytoplankton (tiny, plant-like organisms that live in water) dynamics, all while keeping an eye on the climate’s grand events, from El Niño to La Niña.
Ever wondered how the sea state relates to ocean colour or how waves might tweak future ocean hues? Tensubam’s got the answers, exploring these phenomena in the Southern Ocean, where the world’s strongest winds and waves stir up a storm of scientific discovery.
His work not only sheds light on ocean biogeochemistry but also tackles the crucial role of the Southern Ocean in regulating our global climate. With the Southern Ocean absorbing a hefty chunk of the world’s CO2 emissions, Tensubam’s research is a splashy contribution to understanding our planet’s health.
What is more, his findings may influence future research or policies related to ocean health and climate change. In conversation with Chinglen Tensubam.
Your study talks about surface waves in the Southern Ocean. Can you explain what these waves are and why they are important?
In simple terms, ocean surface waves, as referred to in this study, are the waves generated by wind, either generated locally or from a distant location. The waves we typically see at the beach are a common example. However, in the Southern Ocean, these waves are massive, often reaching heights of over 10 meters during storms and extending hundreds of meters in length. This is due to the region’s powerful westerly winds, which blow consistently over long distances, creating large and long-lasting waves. These waves are important because they facilitate the exchange of heat, gases, and momentum between the atmosphere and the ocean, and drive mixing in the upper ocean. Hence, they form a dynamic part of global climate system.
How do these waves affect tiny plants like phytoplankton, and why should we care about them? How does understanding the effects of surface waves on phytoplankton help us in studying global climate patterns?
Phytoplankton abundance is primarily controlled by the availability of sunlight and nutrients in the ocean. Their concentration increases when both light and nutrients are plentiful. Various physical processes like wind, currents, waves, and eddies can modulate key environmental parameters required for phytoplankton growth, such as ocean temperature, mixed layer depth and nutrient levels.
To understand how surface waves impact phytoplankton abundance, it’s important to first know that the oceans are stratified, with warm and nutrient-poor water sits on top of the cold and nutrient-rich water below. Surface waves can mix through these layers, bringing nutrients up to the surface where sunlight is abundant, thereby enhancing phytoplankton growth. Such influence of wave mixing is more pronounced in the Southern Ocean due to its prominent wind and wave activity.
For instance, this wave mixing can reach up to 100-150 m depth in the Southern Ocean. In this way, surface waves influence phytoplankton by altering key environmental conditions like ocean temperature, mixed layer depth, and nutrient levels. This could impact marine ecosystems by potentially altering primary productivity, modifying global biogeochemical cycles, and consequently affecting the global climate.
Understanding the influence of wave mixing in conjunction with the effects from other physical forcings is essential.
Few facts about phytoplankton: Phytoplankton, microscopic plants living in ocean’s sun-lit layer, forms the basis of marine food web and ecosystem, feeding from microscopic zooplanktons to multi-ton blue whales. They are responsible for absorption of CO2 from the atmosphere to the ocean and release of oxygen through photosynthesis.
Photosynthesis is a process by which phytoplankton uses sunlight, CO2, and nutrients to produce their food and oxygen, thereby playing a critical role in the global carbon cycling. Hence, they are sometimes referred to as Ocean Forest. Although they are microscopic in size, the global scale of their collective photosynthesis is enormous and currently estimated to be of the order of 50 giga tons of carbon per year.
In addition, roughly 50 per cent of oxygen we breathe comes from the ocean, primarily produced photosynthesis of marine phytoplankton. Hence, shifts in phytoplankton populations can significantly impact the global climate system, as well as have cascading effects on marine ecosystems as they are the basis of the system.
Therefore, understanding their variability is crucial for ocean health and management in the face of environmental change. Historically, investigations into marine phytoplankton dynamics aimed to elucidate variations in fish stock abundance. Today, research endeavours are predominantly motivated by their crucial roles in regulating global biogeochemical cycles and mediating global climate system as a whole.
Why are the Southern Ocean’s winds and surface waves so unique compared to other oceans?
The Southern Ocean is a unique wind-wave generation environment because of its continuous expanse of water encircling Antarctica, driven by strong westerly winds and a vast, nearly infinite fetch (uninterrupted distance over water where wind blows), except for a constriction of nearly 1,000 km along the Drake passage. This results in massive waves and powerful currents, unlike other oceans, which are bounded by landmasses and have shorter fetches.
What gaps in current research led you to investigate the impact of these large waves on biogeochemistry?
Despite the significant effects of surface wave mixing, there has been no previous research focusing on how this wave mixing impacts oceanic biogeochemistry, particularly phytoplankton distribution, or how surface waves might alter key environmental parameters required for phytoplankton growth in the Southern Ocean.
This gap may be due to the complex role of surface waves in the global climate system and the difficulties in parameterising their effects in ocean or climate models, despite their substantial impact. Although some similar studies have investigated the role of surface wave mixing on different ocean responses, such as ocean heat content, sea ice, and tropical cyclones, this study addresses a critical gap in Southern Ocean biogeochemistry research that has been overlooked.
Additionally, the effects of wave mixing should not be disregarded in the Southern Ocean due to its prominent wind and wave activity. This work provides a foundation for understanding the complex interactions between wave dynamics and marine ecosystems.
With climate change affecting winds and waves, what changes do you expect to see in marine life and the ocean’s chemistry? How does your research help us understand these changes?
Previous studies have reported that the Southern Ocean is undergoing significant physical and biogeochemical changes, including warming temperature, diminishing sea ice extent, rising sea level, increasing stratification, and acidification. In addition, wind speed and wave heights are in increasing trends in the region. These environmental shifts are expected to have profound effects on marine life, particularly on phytoplankton, which form the base of the marine food web and drive key biogeochemical cycles. Our research sheds light on how surface waves, through enhanced mixing, can affect phytoplankton distribution and growth by altering nutrient availability and other environmental parameters. Understanding these interactions helps us predict how changing wind and wave patterns may impact marine ecosystems, from primary productivity to broader climate effects.
What are some of the practical implications of your findings for the broader scientific community and for climate research?
Firstly, this study highligjts the crucial role of surface wave mixing in influencing the physical and biological dynamics of the Southern Ocean. The observed changes in phytoplankton distribution and nutrient levels due to wave mixing, along with variations in sea surface temperature and mixed layer depth, could impact marine ecosystems by altering primary productivity, global biogeochemical cycles, and the global climate system. This approach can also be extended to investigate other critical biogeochemical variables, such as dissolved oxygen, alkalinity, primary productivity, and dissolved organic carbon.
This study will complement ongoing Southern Ocean research related to ocean health and climate change and could inform future investigations into how changes in wave climate might affect the oceanic biological pump, with broader implications for the global climate system. Furthermore, the altered upper ocean dynamics due to the additional wave mixing will change ocean feedback to the atmosphere and vice versa.
What challenges did you face while conducting this study, and how did you overcome them?
This study requires supercomputers for running models, validating results, and analysis, making it computationally expensive. We faced some challenges while incorporating the surface wave mixing parameterisation into the ocean biogeochemical model we used in this study. Because such parameterisation is not a part of regular routines used in ocean models.
We overcame these challenges through thorough testing, guidance from supervisors, collaboration with experts to ensure the robustness of our findings. We duly acknowledge the National Computational Infrastructure and the University of Melbourne for providing the required compute resources.
Can you describe any practical applications or real-world impacts of your research on coastal communities or marine industries?
There are growing studies investigating the impact of changing wind-wave climates on coastal environments and management, focusing on issues like coastal erosion, sediment deposition, and storm surges. While our research primarily targets the Southern Ocean due to its pronounced wave activity, the methodologies and findings could be applied to coastal environments as well. Conducting similar experiments in a high-resolution coastal ocean model could help us assess its impacts on coastal biogeochemistry and ocean health, including the risks of harmful algal blooms and sediment suspension, and improve coastal management strategies.
The Indian Sun acknowledges the support of the Victorian Government.
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🌊 Chinglen Tensubam’s research on Southern Ocean surface waves & their impact on #marine #ecosystems is groundbreaking for #climatescience. 🧪🌱 Curious about how waves affect our #oceans' health? Dive into his fascinating work now! 🌍🔬 #TheIndianSunhttps://t.co/5f91P3N7qG
— The Indian Sun (@The_Indian_Sun) September 13, 2024
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