The Earth's oceans are a mix of algae, plankton, and bacteria which absorb large amounts of carbon dioxide while producing 50% of the planet's oxygen.
For several decades, Earth-observing satellites could not set apart the individual species, hampering the attempts to study their influence on Earth's climate. It also poses challenges in studying the impact of global warming to this foundational component of the climate system.
Role of Phytoplanktons and Aerosols in Earth's Climate
Large phytoplanktons, which dominate in cold waters, are a fortress of carbon storage. In the marine food chain, these big cells get eaten by big zooplankton. The carbon in the waste likely reaches the ocean floor and stays safely sequestered. In the warmer waters at lower latitudes, smaller phytoplanktons live, and the carbon in their waste is consumed by microbes and is ultimately emitted back into the atmosphere.
Meanwhile, aerosols can have a profound impact on climate by scattering or reflecting light. The cooling of the atmosphere and the absorption of light are primarily based on the physical properties of the aerosols. While they are considered air pollutants, aerosols actually have an important role in climate by masking the warming of greenhouse gases.
Exploring the Unknown in Air and Water
A $964 million satellite from NASA is about to offer a breakthrough in studying these climate factors. After surviving delays during the pandemic and four cancellation attempts by former US President Donald Trump, a new Earth-observation satellite is finally set to launch aboard a Falcon 9 rocket from Cape Canaveral Florida no earlier than February 6.
The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission is designed to extend and improve NASA's 20-year record of satellite observations of global ocean biology, clouds, and aerosols. Its main goal is to study phytoplankton, algae, and tiny plants to monitor ocean health and provide insight on how the ocean and atmosphere exchange carbon dioxide.
The satellite's primary instrument serves as NASA's first "hyperspectral" imager to fly on a major geoscience mission. Instead of collecting reflected light in a few discrete channels, the instrument separates light into more than 200 channels which can distinguish various pigments used by phytoplankton.
PACE also has sharp color vision which can help track human impacts on rivers, lakes, and coastlines. This is done by separating natural species from dissolved organic matter or bacteria associated with fertilizer or sewage runoff. It will also explore the role played by eddies in driving the movements of plankton species and the nutrients they rely on.
Through these features PACE is expected to restore NASA's ability to study small aerosol particles and clouds. It has an advanced polarimeter designed to capture polarized light and show the influence of aerosols to the growth and life span of clouds. By identifying the size, type, and abundance of particles, the polarimeters can fill out the inventory of aerosols, including the sea spray formed over the ocean.
According to PACE project scientist Jeremy Werdell, PACE represents a major effort in combining ocean research with atmospheric studies. They are confident to go beyond just seeing change in Earth's climate to better understand why the change actually occurs.
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