Light and the Oceans Part 1: A Long Journey

This is Jim Fiorendino, your host for On the Ocean. The ocean is a dynamic environment. Currents like the Gulf Stream, flowing northward along the east coast of the United States, transport huge quantities of water from the equator towards the pole. Microorganisms fix carbon from the atmosphere into a biologically available form. Massive tropical cyclones form each year during hurricane season, fueled by heat trapped in the oceans. What do all these processes have in common? They are all driven by energy from the sun.

Through the process of nuclear fusion (above), our sun joins two hydrogen atoms to create one helium atom, releasing heat and energy. That energy, which we call light, travels 93 million miles to reach planet Earth. Light reaches Earth from the Sun at a variety of wavelengths, or energy levels. Some of these wavelengths are harmful; wavelengths we can see, known as the visible spectrum, range from about 400 nm to 750 nm. Most of the light that reaches Earth is within this range, but the full range of wavelengths extends from 200 nm to over 2000 nm.

Wavelengths of light reaching Earth from the sun; the majority of light reaching Earth is within the visible spectrum (400 – 750 nm) Image from: https://i.stack.imgur.com/yTUFf.png

In the atmosphere, light is scattered, absorbed, or reflected by particles and gasses. Light at blue wavelengths tends to scatter most, which is why, on a clear day, you will see a blue sky. You may be familiar with the ozone layer, a section of the atmosphere in which a high concentration of ozone can be found. Ozone is a molecule of three oxygen atoms and is excellent at absorbing harmful ultraviolet radiation. By the time light reaches the ocean, only about half of the radiation that first reached the atmosphere remains.

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.

Script Author: James M. Fiorendino

Contributing Professor: Dr. Lisa Campbell

Featured image from: http://unasd.org/climate-actions-oceans-literacy/ocean-underwater-light-wallpaper-3-1/

Texas A&M Graduate Student Spotlight: Modeling Hypoxia

Imagine if all the oxygen were sucked out of the air where you lived. Pretty terrifying, right? This is a major problem for marine life in areas of the ocean where dead zones form. Dead zones develop when dissolved oxygen at the bottom of the coastal shelf reaches critically low concentrations that are harmful to the organisms living there. A “dead zone” develops every summer in coastal waters off the Texas and Louisiana coast, and has been a major concern of scientists for decades.

Map of hypoxia in the Gulf of Mexico, from: https://gulfhypoxia.net/wp-content/uploads/2018/07/2018_SW_BDO_2018-07-27_ALL_web.jpg

Mapping the region affected by low-oxygen bottom water is essential to understanding the dynamics of dead zones. This is not an easy task. Each year a research vessel maps the hypoxic region of the Texas-Louisiana shelf (hypoxia refers to low-oxygen conditions), but the marine environment is constantly changing, and during the week it takes for a ship to traverse the region experiencing hypoxia, the shape of the dead zone has changed.

Below: Bottom oxygen simulations for August – September 2010 on the Texas/Louisiana Shelf. Harmful low -oxygen concentrations form mobile patches. Simulation made by the Physical oceanography Numerical Group (PONG) at Texas A&M University using the Regional Ocean Modeling System for the Texas-Louisian shelf.

To better inform direct sampling in the field from a research vessel, scientists use mathematical models that simulate ocean currents and conditions to approximate the formation and changes within dead zones. These ocean models resemble the atmospheric models used to predict weather and are based on equations that describe physical processes, all interpreted by powerful computers. One advantage of using models is the ease with which scientists can run experiments where some mechanisms or environmental conditions within the model are altered. The model responds to these changes, giving scientists important insight to the processes at work within marine environments. For example, scientists can explore how the area of the hypoxic region will change if the freshwater input from the Mississippi river increases or decreases, or how storms of different strengths can disturb the hypoxic region by mixing the water on the Texas-Louisiana shelf. Models are not perfect; they are often limited by data or do not capture all the dynamics of marine ecosystems, but models and field observations, when used to complement one another, greatly improve scientists’ understanding of marine systems.

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.

Script Author: Veronica Ruiz Xomchuk

Editor: James M. Fiorendino

Contributing Professor: Dr. Kathryn Shamberger

Texas A&M University Graduate Student Spotlight: Deep Sea Corals

Coral reefs, like the Great Barrier Reef in Australia, are some of the most brilliant and biologically diverse ecosystems in the oceans, but did you know there are corals in the deep ocean, too? In fact, most species of coral are found at depths below 1600 feet, where they grow to be thousands of years old. These deep-sea corals are a very important habitat for deep-water fish, and they are of interest to scientists because, like shallow water corals, a record of past ocean climate conditions is stored within their skeleton. These coral archives can fill in gaps in our understanding of the deep ocean that help scientists piece together the history of Earth’s oceans and climate. Of course, living at such great depths makes these corals difficult to study. Using advanced technology like Remotely Operated Vehicles and deep-diving submersibles allow scientists to study the environment of deep-sea corals.

Locations of deep-sea coral communities along the Hawaiian-Emperor seamount chain. Photo provided by Sarah Hall
Locations of deep-sea coral communities along the Hawaiian-Emperor seamount chain. Photo provided by Sarah Hall

Researchers in the department of Oceanography at Texas A&M are currently engaged in research regarding deep-sea corals, specifically the effects of humans on deep-sea coral ecosystems. Current areas of interest include the Northwestern Hawaiian Seamounts, with a focus on Corallium, a precious coral sometimes known as red or pink coral. Precious corals are used for jewelry, but are also accidentally damaged or destroyed when deep-sea commercial fishers use nets that drag along the sea floor. Scientists study different areas of the Hawaiian seamounts, comparing non-fished areas with regularly-fished areas, and areas that have been recovering for the past 40 years following the expansion of the US Exclusive Economic Zone, or EEZ, which limited fishing activities that fall within the EEZ. Studying deep-sea coral recovery after damage by fishing activities will help determine the sustainability of fishing practices, and help develop effective management and conservation strategies.

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.

Script Author: Sarah Hall

Editor: James M. Fiorendino

Contributing Professor: Dr. Kathryn Shamberger

Texas A&M University Student Spotlight: Tracking Monsoons with Thorium

Understanding ocean processes often requires a little detective work, identifying clues left in the marine environment for scientists to find. The Niger River’s flow and discharge are controlled by the amount of regional precipitation in West Africa. West Africa’s regional precipitation is controlled by the west African monsoon, when winds shift seasonally causing both a wet and dry season. Changes in monsoon intensity can affect the stability of regional infrastructure, as well as financial and food security.

Changes in west African monsoon intensity as a response to climate events can be studied by looking at the sediments deposited in the Niger River Delta. An isotope is an element with a specific number of neutrons in its nucleus; some isotopes in marine environments can be used as tracers, informing scientists about chemical or physical processes. Uranium and thorium-230 isotope ratios in sediment can be used to estimate rates of sediment accumulation, and if the sediment has been transported to or from the surrounding area.  If the amount of thorium-230 found in the sediment is higher than the theoretically-estimated amount, new sediment has been transported to the area and if it is lower, sediment has been removed.

Shifting of the Intertropical Convergence Zone is responsible for monsoons.
Shifting of the Intertropical Convergence Zone is responsible for monsoons.

 

Another form of thorium, thorium-232, can be used to study sediment sources. Thorium 232 is virtually entirely derived from continents.  Previously, thorium-232 was only used to study the amount of windblown sediment to the open ocean.  However, current research in the department of oceanography at Texas A&M is hoping to expand the use of both thorium 230 and 232 to study changes in the delivery of sediment and other material to the ocean by rivers. Since the Niger River’s flow and discharge is controlled by the amount of regional precipitation, and West Africa’s regional precipitation is controlled by the west African monsoon, the amount of sediment delivered by the Niger river should reflect the intensity of the monsoon.

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.

Script Author: Ruby Schaufler

Editor: James M. Fiorendino

Contributing Professor: Dr. Kathryn Shamberger