DISCUSSION: Clouds have a dramatic impact on weather and climate. During the day, clouds reduce incoming solar radiation at Earth’s surface, resulting in cooler daytime high temperatures. Clouds have the opposite effect at night. They reduce the amount of longwave radiation escaping to space which leads to warmer minimum temperatures. Thus, clouds that occur at different times can have very different impacts. Different types of clouds can also, exert different impacts. For example, low-level, layered clouds (e.g., stratus, stratocumulus, etc.) reflect a lot of incoming solar radiation, but emit about the same amount of longwave radiation as the surface. Thus, the net effect of low-level clouds is a cooling effect. In contrast, because high-level clouds radiate much less longwave radiation than the surface, they effectively “trap” that radiation and have a warming effect.
Clouds are one of, if not the biggest, source of uncertainty in our future projections of climate partly due to the fact that clouds can have opposite effects depending on what type they are and/or when they occur. In addition, the polar regions are warming faster than the rest of the planet. Thus, understanding cloud cover in the Arctic is critically important for understanding future climate there and globally.
A recent study by Jessie Creamean out of Colorado State University (CSU) may add to our understanding of clouds in the Arctic. The picture above shows an example of a phytoplankton (single-cell, plant-like organisms) bloom in the Chokchi Sea northwest of Alaska. When this phytoplankton dies, they descend to the ocean bottom where bacteria consume and break down the dead organisms. The CSU study found that these bacteria can be mixed up to the surface and can become airborne in strong winds over open water. Clouds cannot form without some surface or particle in the atmosphere to condense or freeze onto. Further research needs to be done in the Arctic, but elsewhere, bacteria have been shown to form effective surfaces on which freezing can happen, facilitating cloud formation. It is possible that as the Arctic warms, and there is less sea ice, more of these bacteria may get into the atmosphere and enhance cloud formation. Because clouds are primarily low-level, layered clouds in the Arctic, enhanced cloud cover may have a cooling effect and form an important negative feedback on climate in that region. Again, the CSU study only showed that these bacteria can more easily get into the atmosphere with strong winds over open water. Further work needs to be done to confirm the connection between these bacteria and clouds and any potential relation to the climate of the Arctic.
To learn more about other interesting Arctic and Antarctic weather topics, click here!
© 2019 Meteorologist Dr. Ken Leppert II