24 September 2018

Back on the heat highway

...but things look a little different

We’re nearing the end of our Arctic research cruise. The ship is due back in port in Nome on the morning of September 30th, so accounting for the few days of transit time back across the Chukchi Shelf and through Bering Strait, that leaves us only a few days to continue sampling.

So far, we’ve divided our time into three distinct sampling modules. First, we were at the shelf break, next we we in the remnant ice pack, and finally we were in the deep waters of the Canada Basin. In each of these regions, we made measurements of the ocean to try to understand the processes that control stratification. The shelf break is a dynamic region with several water masses of different densities coming together and a warm current meandering and eddying along the shelf slope and delivering packets of heat to the deep ocean. In the main basin, heat from the sun warms the surface and is mixed down by the winds. Ice grows and melts changing the salinity of the upper ocean. But the effects of coastal processes also reach the main basin. In our last few days, we’re trying to link all the pieces together. We’ve traded in our squiggly exploratory ship tracks that served us well for honing in on small scales for long strait lines which connect the distinct regions. Our mission is to find the transition zone where the jet of Alaskan Coastal Water shooting through Bering Strait ends and where the true Arctic begins.

Last week when we were sampling just off the shelf in the remnant ice pack, we found a strong plume of close to 7° water, meandering a bit, but predominantly flowing strongly to the southeast. It was associated with a surface feature we could see in the satellite SAR image and looked like a warm current that had come around Point Barrow, separating from the coast, and heading eastward to melt some of the lingering ice.

Now, less than a week later, it looks like eddies have broken off the current, or perhaps the jet is meandering more and we’re passing through several of those meanders. Both of those things could be true! Or neither! This is where the detective work of oceanography comes in - pulling all the fragmentary pieces of data together to form a complete story so that all the individual observations fit. Hopefully we’ve collected enough measurements from the ship, from our floating assets, and from the sky, to convincingly describe the dynamics of this meandering plume.

A couple descriptive terms have made it into the colloquial language of the lab to refer to some of the features we’ve seen - “the crab” for the first big blob of water we encountered, and “the mushroom” for the 7° plume that made billowing shapes in the ice edge.

There has been some discussion lately about renaming these features with more official scientific terms (think eddy vs blob). Harper Simmons suggested that the mushroom be referred to as “the SODA fountain.” It definitely doesn’t meet the requirements of being more accurately descriptive but it is so pun-ily satisfying and I quite like it. Let us know if you have any other suggestions!