I'm Tim Stanton. I'm at the Moss Landing Marine Labs in the Naval Post graduate schools, and I'm an Emeritus Professor, and we've just deployed the distributed network as a component of Mosaic Project in the integral output. I'm going to be giving a lecture on the ice ocean atmosphere coupling. I hope you enjoy that. We've just come in after the academic Fedoroff, where we took the first part into a nice warm reading room. I'm going to be talking about the ocean atmosphere coupling in the Arctic, and posing the question, how does the presence or absence of ice change the connections between the atmosphere and ocean? So very briefly, the outline is looking at the way wind couples to ocean currents, how vertical heat transport between the ocean and atmosphere is moderated by the ice, and how solar radiation enters the ocean in the presence or absence of ice, and touch on the ice-albedo feedback, which is very important in the central Arctic these days. Then mix it in a few slides, looking at Mosaic measurements of these processes. So wind forcing of the ocean is a very important thing in driving surface currents and mixing in the ocean. So when the wind blows over a surface, the amount of its momentum, which is simply the mass, times the speed of the wind that passes to the surface, depends on the surface roughness. Now surprisingly, the ice covered ocean is much smoother than the open ocean with waves on it. So we can expect stronger wind driven currents in the central Arctic during the summer, when there's more open water conditions. That has quite a few ramifications, particularly as we go to a more ice-free condition for longer times in the Arctic. This diagram shows paths for the heat to-and-from the ice. It's a cartoon version trying to summarize the various ways that heat can get into the upper ocean. The first thing is the sensible and latent heats. That's the evaporative heat. For example, heat lost when the water evaporates is a latent heat, and then the atmospheric sensible heat is just when the atmosphere for example, is colder than the ocean, which is very typical, we lose heat from the ocean to the atmosphere. Very important thing in the summer, is the solar radiation and put into the ocean. That's really quite tricky. It depends on the reflectivity of the surface, presence and absence of melt ponds and many other factors, which greatly complicate that, particularly when we tried to model it. The last thing I wanted to bring up is the small heat flux that comes from the heat contained deeper within the ocean, primarily from inputs from the Pacific and the Beaufort Gyre and the Atlantic, water coming in from the other side of the basin, for example, with the Mosaic side is on the Siberian side of a base, and this becomes important. But it's not very available heat, and we're going to discuss that in another talk. So heat transport between the atmosphere and ocean moderated by ice, you need to consider the following factors. Ice is a fairly good thermal insulator. So as soon as ice begins to form, the transfer of heat from the relatively warm ocean, which is always very close to the freezing point of these ice around. In this case, about minus 1.9 degrees centigrade to the atmosphere which can be anything from minus five to minus 40 degrees C, is rapidly decreased. Now, snow is a very good insulator, so even a few centimeters of snow, significantly reduces the conduction of heat from the ocean to the atmosphere, even if the ice is doing a pretty good job, that snow just kills it. So the presence of ice and snow greatly reduces the thermal coupling between the ocean and atmosphere. In cold winter conditions, openings in the ice, which are called leads, expose warm ocean water at the local freezing point again, to the very cold atmosphere, and can cause very large heat losses to the atmosphere over these local areas. It really depends on the size of whether these are significant or not. Turns out they are, greedy in the heat balance when we consider a whole annual cycle. Ice is highly reflective to incoming solar radiation or sunlight, with about 60 percent of the light being reflected. Snow is even more reflective with 95 percent of the light reflected, and the albedo is simply the fraction of reflected sunlight. For example, 0.95 for fresh snow. However, open water absorbs about 94 percent of the incoming heat, with six percent reflected. This makes the Arctic ice pack very sensitive to the amount of open water that is in a given area, the open water fraction, and leads to the important ice-albedo feedback that contributes to rapid late summer ice melt. So the ice-albedo feedback is an extinction of what I just said. The big difference between snow and ice-albedo, illustrated in the left-hand panel, and the low albedo or the water in the right-hand section of that figure. I'm showing that just about all the incoming solar radiation enters the ocean, and this gives rise to a feedback. So let's consider in the mid-season and the mid summer we start to get some melt ponds and some open water forming. So we melt some ice, cause some freshwater to be generated, we lower the albedo because that open water now absorbs a lot of solar radiation. Now we increase the absorbed sunlight into the ocean, and that causes more melting of the sea ice, and around we go. So it's a positive feedback, and you really do see this playing out in the central Arctic in the summer, to the extent that we really get rid of just about all the ice in the Beaufort Sea now by late summer. This is something we do not entirely understand, that basic paradigm is playing out. That when we model it, we failed to get quite the rapid retreat that we actually observe. This is illustrated here in a photo of the Sheba Ice Camp taken in full in 1997, with a hotel ship behind, and the ice camp in front, and you can see snow covered ice and no holes in it, just happy people wandering around. Whereas a year later, or nine months later, in late summer of '98, you can see on the right-hand side all the melt ponds and the melted out areas surrounding the ship, making it very challenging to work. This is very typical again, even back in the late '90s. This was playing out, and it's playing out even more these days, because the ice retreat is even more rapid by late summer. So I'm going to just show two examples of ocean ice atmospheric measurements in Mosaic. The ocean flux is just below the ice, which is something that I specialize in, and then conductive flux is in the ice, which we make it a number of sites, because it's actually quite a lot of variability depending on snow depth and ice time. I'll just quickly show one example of the atmospheric flux measurements and solar radiation measurements, that are very important in understanding the surface forcing of that system. So I'm going to describe the autonomous ocean flux buoy system, which is my specialty and contribution to the Mosaic Project. There is a schematic on the lift that shows from the top-down and Acoustic Doppler Profiler, that measures current profiles down to about 80 meters depth. A flux package that measures the transport of heat, salt and momentum between the ocean and the ice, measured about two to three meters below the ice. Then below that are some pycnocline SPI, which I'll describe in a different lecture. So the IFB measures heat, salt and momentum fluxes, and the formation and melt of ice locally. Because it's on a carriage system, since a package can move up and down about three meters below the ice and measure temperature, salinity and biological properties including chlorophyll and dissolved organic matter and turbidity, which is very important in the late summer in understanding the way that solar energy is trapped in the operation, and it also measures the local ice space changes and roughness in that system. The other system I'm going to show is a nice simple system. It's an ice conductive heat transport measurement. Which is simply a set of temperature sensors going from the atmosphere through the snow, down into the ice, and out into the ocean. It measures the ice thickness, the snow depth and by knowing the thermal conductivity of the ice, you can infer the actual heat conducted through that system. So I hope that you will show some interest in these measurements and observations as we go through this next year, we hope to get a full year of these measurements as the whole system drifts out towards the Northern Atlantic Ocean.
