rejected banana

I was hired in my post-postdoc position because UAF just got a brand new oceanographic instrument, the Acrobat Towed CTD.  I’ll go into exactly what it does and why we bought it in a later post. But, my job is to put it together, install the science payload, test it, figure out how to communicate with it and program data collection/display for it.

Building an instrument is a really cool process that everyone should be able to see. So I’ll be documenting this all on twitter. I’ll be posting under @SeaGrebe . Follow along from when we received our new instrument at the lab to when it is deployed in the Chukchi Sea this August.

For me, the postdoc has been an opportunity to figure out what I want to do next as an Oceanographer. Initially, I really didn’t know what that was. There was no shining beacon of hope in the darkness that pointed directly to what I wanted to do. I sense I am not the only postdoc that feels this way, so I figured I’d share my story.

First, I spent some time figuring out what I didn’t want to do. That included spending my entire day never leaving my office, pursuing a faculty position at university and writing papers and grants (more about this later). What clued me in was my weekend activities. I liked to tinker. Take things apart, fix them, design homemade cheap solutions for expensive repairs (Full disclosure, I purchased vernier calipers for my household toolbox!). Then my housemate told me, you should really have a job where you take things apart. And I thought, brilliant! 

Since I work best within a framework I decided that I need a really simple goal, but there could be any number of paths that lead to this goal. And that’s how I came up with my simple phrase: I want to throw expensive sh*it in the ocean.  

And phrase is what got me sitting in this lab at UAF putting together a brand new oceanographic instrument. And I am pretty stoked about it. 

Back to the writing bit. I actually used to like writing, but some where between my freshman year of college and my PhD that was beaten out of me. I gotta face facts, I can not have a career doing what I want to do without writing.  So I am trying to write for fun again, such as with this blog.  The post-postdoc has also freed up some time so I can do this.

Between my new job and trying to like writing again, it’s a great opportunity to show what happens “behind the science”, the work put into obtaining physical oceanographic data. I’ll talk more about it in a later post, but if you want to see how a new instrument is prepared for deployment follow @SeaGrebe on Twitter.  I’ll also blogging here and tweeting @rejectedbanana about our upcoming fieldwork in the Arctic.  Hope you’ll follow along!

Surfing the tidal bore in Turnagin Arm Alaska. Photo courtesy of Scott Dickerson.

I’ve been paying so little attention to the news since getting getting back from my latest conference that I sort of missed all the hype about the supermoon this weekend.  But then, I realized the supermoon meant one really exciting thing: SUPER TIDES!!!! (insert witchlike cackle here)

The supermoon occurs because the moon is the closest to the earth it will be all year long. Because of the moon’s proximity, its gravitational pull on the water in the oceans is also stronger. This causes really low low-tides and really high high-tides. The former is great if you are into exploring sea beasties that are uncovered below the normal range of the intertidal zone. The later is only a problem if you left your beach chair and belongings at the normal high tide line on the beach (it is so sad when a cooler full of beer and snacks is washed out to sea). This also means that tidally-generated internal waves (waves inside the ocean) are also bigger than normal, which in my research world is really cool.

But there is another phenomena which supertides can cause, tidal bores. Tidal bores are solitary waves formed as the tide rises in specific regions, such as river inlets and long narrow bays. Unlike Tsunamis, these are a true ‘tidal wave.’ These waves can be over 30 feet tall, travel for miles and can even be surfed! There only about 100 locations worldwide where bores occur, some famous examples include the Trent River in England, Turnagin Arm in Alaska, “pororoca” on the Amazon River, and the world’s largest on the Qiantang River in China. It is almost 30 feet tall and travels up to 40 mph! Tidal bores can also be dangerous, sinking unwitting ships and drowning foolhardy swimmers.

But tidal bores don’t happen all the time. They need a combination of a really really tide followed by a really really high tide. The difference in height, and therefore volume, between the really low and really high tide means a lot of water flows into the bay really fast in the 6 hours between the two extremes. As all this water is filling the bay, water near the bottom slowing down due to friction with the seafloor. But the water near the surface is still traveling at the same speed, now outrunning the water near the bottom. The surface water piles up, forming the crest of the wave. Eventually the face of the wave gets so steep, it topples over, breaking like a wave at the beach. The resulting turbulent whitewater is now a classic tidal bore.  

Tidal bores can also be important for marine ecosystems. They mix up sediment and nutrients: uncovering creatures that were previously buried and attracting all sorts of opportunistic feeders, including piranhas in the Amazon. Belugas have played in them. Moose have unsuccessfully tried to outrun them.

There are a few proposals to harness the power of tidal bores to generate electricity. One small power plant is in operation in the Bay of Fundy, but has had some problems such as trapping whales.

This Piranha only wants you to surf the Pororoca in Brazil if you are tasty.  

For my PhD, I studied deep tidally-generated bores that occur in the ocean near the base of the continental slope, over 1 mile beneath the surface. These babies can be huge, over 600 ft tall! They dwarf the largest surface tidal bores observed in China, but are much slower, traveling at less than 1 mph. While surface tidal bores may be rare, there is evidence that these bores are much more widespread occurring all over abrupt bathymetric features like continental slopes, seamounts, mid-ocean ridges, etc.  They are also turbulent like their surface counterparts. Therefore they may be an important mechanism that exchanges water and nutrients between the deep and shallow oceans. 

So the supermoon is not only a really awesome astronomical spectacle, it has consequences here on earth too. And supermoon will cause insanity and hysteria, but only for the surfers that will be jumping into freezing or piranha-infested waters to surf the tidal bore this weekend!!