Hi everyone. My name's Jessie Creamean and I'm a research scientist at the Colorado State University. I'm on Mosaic because I'm a funded PI to look at aerosol cloud interaction measurements throughout the entire year. Right now, I'm on the Akademic Fedorov Icebreaker. We are at about 85 degrees North, just a little bit North of that. We're awaiting the arrival of the polar shared defined, an ice flow to set up the entire network on. Today I'll be talking a little bit about aerosols and how they affect clouds and precipitation in the atmosphere, and also why they're important in the Arctic. Basically, an aerosol particle, what is one? An aerosol is essentially a liquid or a solid that's suspended in a gas. In this case, we have the atmosphere, that's the gas. There are aerosols that come from natural sources. We have sea spray, mineral dust, there are vegetation that emit aerosols into the atmosphere. Then we also have anthropogenic aerosols, things that come from traffic, from combustion sources, from agriculture. Those are things that humans produce. In order for an aerosol that originates as a particle on the ground essentially it's become airborne, you need wind in the equation. Things like desert dust, sea spray coming from the ocean surface, soot coming from trucks, and then also gases emitted from these different sources like trees and agriculture and cars. Those can be emitted into the atmosphere and undergo reactions where they can become aerosol particles. These things could emit into the atmosphere by winds, and then they can get carried thousands of thousands of kilometers up into the atmosphere. Aerosols are important once they enter the atmosphere because they can have effects on the radiation budget. Certain types of aerosols that atmosphere like, sea salts basically act like little mirrors and they can actually reflect solar radiation back into space. If you have other aerosol types like soot coming from trucks, those things tend to absorb energy in the atmosphere, causing it to heat up. Now, if you have aerosol particles of different compositions and size, they can actually act as seeds for cloud formation. You can think of a cloud like a plant, it basically need seeds to grow. These types of aerosols are called either cloud condensation nuclei or CCN. Our ice nucleating particles or IMPs forming either liquid droplets or ice crystals in the cloud. These clouds that use aerosols form can then either scatter radiation back to space, or they can actually act like a blanket in the atmosphere and trap energy entry into the Earth's atmosphere. Aerosols, once they're in clouds, they don't only affect the solar radiation, thermal radiation in the Earth's atmosphere. They can also affect how clouds precipitate. Let's say we have a pollution plume and you have a cloud form from all of these little pollution particles. What happens is you have a lot of these little droplets that are competing for any available water vapor, and that tends to inhibit precipitation coming from a cloud because they take longer to grow into precipitation sized droplets. Now on the other hand, if you have ice nucleating particles in a cloud like mineral duster bacteria, those things form this really large ice crystals that can grow faster into precipitation. What's typically thought is that under a lot of conditions, the ice nucleating particles or IMPs, can actually cause clouds to rain or snow out. This in fact, is inherently dependent on the number of them, their chemistry, and also their size. Specific to the Arctic, these effects are really important, namely aerosol effects on clouds, because they can have a role in Arctic amplification and so basically, as the Arctic is getting warmer year-to-year, we have these compounding effects that's causing it to accelerate its heating. For example, when we have the sea ice thawing out, you have darker ocean surface that's being exposed that can absorb more heat and energy and so that contributes to additional warming. We also have permafrost that Stein. As the soil that's remained frozen for thousands of years is thawing out, these reserves of greenhouse gases are being emitted into the atmosphere, so that's causing an additional warming as well. As a result, the Arctic is warming at least twice as fast as the rest of the globe. It's affecting air and circulation patterns all over the world, not just in Arctic.. My question is: specifically, how aerosols in clouds is playing a role in this process? Aerosols have effects on the Radiation Budget, precipitation, cloud lifetime, cloud radio forcing, but it's also really important for energy reaching the sea ice surface. You can see a lot of clouds in the atmosphere today that might be acting to trap heat in or reflect solar radiation away from the sea ice surface. Aerosols again play a big role in this. A lot of previous work has gone into trying to characterize Arctic aerosols. Generally, what we've found is that in the winter and the spring, we have transport of pollution coming up from mid-latitudes. This is known as the Arctic Haze Season. Basically, we have a lot of aerosols coming up into the Arctic. However, in the summer, we tend to see this transport start to die off, and then we also have more precipitation that's removing these aerosols from the atmosphere that are making their way up there. So the arctic resumes to a more pristine or clean conditions where we have local aerosol production from things like ocean biology and vegetation. Although we have a pretty good grasp on the annual cycle of aerosols, there's still a lot remaining uncertainties associated with not only the observations, but especially modeling the aerosols and how they affect clouds and radiation. Specifically for the biology, that is a really important thing in the Arctic in terms of aerosols. However, there's not a lot of work that's been done on it. That's why people like me are here to try to understand a little better. How does biology in the Arctic effect aerosols? We have local and distant sources of aerosols. I had mentioned that pollution can get transported up here, but also so can biological aerosols from things like plants, mineral dust, can be transferred up here. Biomass burning smoke, which can have some vegetative aerosols in it, those can also be transported up to the Arctic. We also have tundra in the Arctic that can contribute to the biological aerosols found in the atmosphere. Then we have the ocean. Once the summertime hits, we have more open water, you have biology in the ocean that are being more productive once you have the sunlight available, and those can produce a lot of aerosols that enter into the atmosphere. So these microbes that are in the ocean not only produce aerosols themselves from gases, they produce these sulfur gases, they can emit a lot of sulfur into the atmosphere, and those can then form aerosol particles that can act as cloud condensation nuclei. But they're also particles themselves, so they can emit as whole selves into the atmosphere, they can have fragments. So there are cells that are emitted or they produce these products of macro molecules or proteins, that can then be emitted into the atmosphere and act as ice nucleating particles. These can happen from winds or waves that are hitting the ocean surface and causing these things in the surface waters to become airborne. My work recently has actually focused a lot on that specific process. I'll give some examples of my previous work in the recent years and how that ties into Mosaic. I've been on an icebreaker the last few summers going through the Bering and Chuckchi Sea. Basically the focus was to evaluate the biological or marine sources of aerosols that could potentially contribute to aerosol cloud interactions in the atmosphere. We used to observe some pretty interesting cases. So far we've seen things like a really persistent phytoplankton bloom in the Bering Strait that was emitting these ice nucleating particles into the waters, being transported hundreds of kilometers away into the Arctic Ocean, and then becoming airborne and potentially affecting clouds there. I've also been on the North slope of Alaska, on the coastal location in Prudhoe Bay. The purpose of that study was actually to evaluate local industrial emissions in the Arctic, because it's the third largest oilfield in North America. What we unexpectedly saw, was that marine and terrestrial aerosols are actually contributing to dice nucleated particles there. So pollution, not a very good ice nucleating particle. But once we had the water start to open up during the melt season and also some of the tundra start to open up, that's when we really saw all these different aerosol particles coming into polluted location and really affecting the ice nucleating particle populations. Specifically for Mosaic, both of those things tie in. We have the ocean, obviously, because we'll be right over it. Will be mostly on sea ice. But once we have things like leads or melt ponds where we do have direct interaction between the ocean atmosphere, we really want to look at how those biological processes that are happening there affecting the aerosol population, and then potentially contributing to cloud condensation nuclei or ice nucleating particles. One of the questions is we're going to be really high up in the Arctic, we already are. So are those sources that we see at lower latitudes, are they affecting the aerosol population there? Do we have more local influences versus those long-range sources? Specifically, how does the biology in the ocean effect the aerosol population, but also there are microbes and algae that live in the sea ice and snow. Are those actually making their way to the surface and being kicked up by winds and affecting air sulfide interactions and also using all these observations and putting them into models to better constrain how clouds form in the Arctic.
