Tall waves could mean more ice-forming clouds, according to study that seeks to improve climate models

TORONTO —
Could the height of waves in freezing cold water have something to do with how ice forms in clouds? According to new analysis of a research vessel’s trip through the Chukchi Sea, there could be a connection, one that could help make climate models more accurate.

As global warming causes more sea ice to melt in the Arctic region, it allows for stronger winds to whip up taller waves, sending sea spray high into the air. The new study, published last month in the journal Geophysical Research Letters, looks at how particles flung from waves could promote the development of ice-forming clouds.

The formation of clouds, and how exactly it occurs, is an important part of weather systems, and helps us understand how to track something called the surface heat budget: how much heat is required to make a respective body of water’s temperature rise from its winter minimum to its summer maximum. This surface heat budget then informs climate models that researchers use to track climate change.

“The insight gained from this study is very important if we are to accurately predict the effects of global warming on the Arctic,” a press release stated.

This new study looks at data collected in November 2018, by a research vessel on an Arctic cruise in the Chukchi Sea, north of the Bering Strait. The ship was taking meteorological observations and analyzing the different types of organic particles that sea spray throws up into the air from the peak of waves.

In order to take these measurements, researchers on the ship launched particle sensors into clouds using balloons. They also took measurements from different depths of the ocean itself to understand how the roughness of the ocean on any given day is related to weather and the oceanic particles interacting with clouds.

The particles they were most interested in are called ice-nucleating particles (INPs). These are particles that essentially act as “seeds” in the sky, promoting the growth of ice in clouds by freezing droplets.

During the research vessel’s trip, there were different weather phases. During the first phase, the winds were up, but the temperature of the air was “reasonably high” as well. The air temperature decreased over a period of three days. During a two-day span later in the research, the wind speed hit its maximum, but the air temperature and the water temperature were — at times — differing by up to 10 degrees.

“Sea surface temperature during this month was a record maximum, which promoted the delay of sea ice advance in this area,” the study stated.

The study found that during these high-wave conditions, there was a higher concentration of INPs, which “corresponded to greater quantities of ice crystals in lower-level clouds.” During these conditions, the concentration of INPs increased by a factor of 10 times compared to earlier periods.

When researchers analyzed the aerosols themselves, they found “a high amount of [organic carbon] associated with high content of sea salt” which suggests that a big source of the INPs found in clouds is the sea spray itself.

The Chukchi Sea itself is also a “marine biological hot spot,” the study pointed out. It is relatively shallow and has well mixed ocean layers, in which particles closer to the bottom can be drawn up towards the surface during rough conditions.

The release stated that this discovery puts researchers closer to understanding what promotes ice-forming clouds, which are an important part of understanding Arctic weather.

“Ice clouds reflect much less shortwave solar radiation than water clouds, and thus the phase of clouds greatly affects the surface heat budget of the polar regions,” the release stated. “They may also increase the amount of snowfall, which in turn positively affects sea-ice formation.”

More studies are needed to look more deeply at just how the cycle works, and how climate change interacts with it, but researchers say this puts us a step closer.

“Understanding the relationship between cloud formation and the new sea state originating from the recent Arctic sea-ice decline is critical for skillful weather and sea-ice forecasts, as well as future climate projections,” Jun Inoue, with the National Institute of Polar Research in Japan, said in the release.