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Oceanographer on a ferry

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Ferry.jpg

Since my beginning as a Post-Doc at the University of Maine's EML, I had several opportunities to travel to the west coast... not just to brag about how much more quaint and authentic New-England is, but mostly to share and do my work...  Today I'm back west once again, staying in the Friday Harbor Labs of the University of Washington.  This time is my first participation to a more focused and high-level workshop with seasoned oceanographers under the theme "Global Ocean Ecosystems and Climate".

But before the hardcore science begins, it's time for a short follow-up on a previous blog entry from Andy, while he was traveling this area a year ago.  Andy took an air-borne picture of the northwest part of San Juan Island (Henry Island's shape is unmistakable), and the actual route taken by my own ferry.  Andy is an accomplished oceanographer (and incidentally my boss), so please praise with me his instinctive analysis, in which he correctly guessed that the difference in surface waters' reflectance was caused by oily algae products.

The first picture below shows the intricate smooth and rough surface water features he talked about from a ferry's deck point of view.


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The second, though a little blurred, shows what's in the slicks: algae washed off from the shore!


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Add these two blog entries and you get the idea behind modern oceanography. Just replace the iPhone shot from a plane by a few $M satellite sensor and a couple of unreliable Canon PowerShot pictures with a few $100K scientific sampling cruise. Now you know how oceanographic knowledge is acquired and validated.  Next step, integrate everything and fill the gaps with models... Hey, that's what we happen to do in the EML!

 

Stay tuned for daily updates on this workshop (that's my resolve, for now...).

 


Well, I thought that I could get away with it, but I was wrong. I've been here since the end of March, and I've avoided writing in the EML blog. Not intentionally, I hasten to add... well, maybe a bit. Doesn't mean I haven't been reading it though!


I've been here on a short term contract, working on the sea surface photogrammetry project. But it's not the project that I decided to write about. Based on a comment made by Andy in my presentation yesterday, I wanted to write a bit more about the size of oceans. Andy (here) and Pete (here) both recently wrote about sizes, and what they compared to, so I figured that I'd join in.


I've been lucky enough to travel to most corners of the world for my work. I started in Bangor (North Wales, not Maine) where I did my undergrad, and then headed to Dunedin, New Zealand for my Masters. Total separation: 11889 miles, or in keeping with weird comparative measurements from previous posts, 382662 Olympic Swimming Pools (OSPs), 174369 American Football Fields (AFFs), or my favourite, 1.12415 x 10^7 Smoots, plus or minus one ear. If you think that is the longest distance travelled by an oceanographer, keep reading!


After New Zealand, I headed to Bermuda (a mere 9411 miles, 302902 OSPs, 138024 AFFs, or 8.89842 x 10^6 Smoots) where I worked on the BATS project for several years. That's the Bermuda Atlantic Time-series Study. Nothing to do with flying, squeaking furry mammals. That was a multi-disciplinary project that studied the full ocean depth just off Bermuda. Full ocean depth was 4200m, or 2 and a bit miles, or half the height of Mt Everest. The project had run for over 20 years, and in that time the various ships had travelled the equivalent distance of once round the world at the equator, or about 25,500 miles!


The coolest thing about studying there was when I found out that water can be given an age depending on its depth. At 4200m, the water hasn't been on the surface for nearly 1000 years! It just gives you an idea of how much information the deep ocean can give us. BATS was only one point in the ocean. We actually know more about the far side of the moon than we know about the deep ocean.


Anyway, enough digressing to small distances. Not satisfied with 3 continents, I moved on to my fourth. I worked for a year in Brazil, which was 4046 miles, 130219 OSPs, 59337 AFFs or 3.82547 x 10^6 Smoots from Bermuda. The work there was for an oil company, and we used scientific equipment to look at currents and density changes, helping to plan the locations of pipelines. Not quite as deep as BATS; we only studied to 2200m.


Staying with oil, but moving to just the surface, I came to the EMLab at GMRI (4916 miles, 158238 OSPs, 72105 AFFs, or 4.64860 x 10^6 Smoots), which brings us back to the beginning of the blog post. There's still one more step for me though. I leave here tomorrow, 11 June, and I'll be heading cross country to Alaska to start my Ph.D. I've got a 12 day drive to look forward to, where I'll be covering at least 103072 OSPs, 46967 AFFs, 3.02798 x 10^6 Smoots, or in plain English, about 3202 miles as the crow flies.


I got in to oceanography for the chance to travel. In the ten years since I started at University, I've been to 4 continents and travelled the equivalent distance of 1.1 million Olympic swimming pools, nearly half a million American Football Fields, or 31.6 million times the height of poor Oliver Smoot. Hm? In English? I've gone about 33,500 miles in ten years, which is half as much again as the BATS ships managed in 20 years.


Become an oceanographer. See the world. No really, you will.


The Smoot - http://en.wikipedia.org/wiki/Smoot

Oil Spill--Big or Small?

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Several times in the last few weeks, I've heard executives from British Petroleum make statements that their spill (which, incidentally is now the largest in US history) is "small relative to the total volume of the ocean."  According to BP's original estimate of 5000 barrels per day, the spill has "only" released 185,000 barrels as of 5/27.  However, USGS just released a best estimate of 12,000 barrels per day (444,000 total), but says it could be as high as 25,000 barrels per day (925,000 total).  Using the USGS best estimate, 444,000 barrels amounts to only 0.000000000005% of the total ocean or 0.000000003% of the Gulf of Mexico.  As Nick put it, if the spill were actually big relative to the ocean, then we'd really be in trouble.

The problem with viewing the spill in this way is that it assumes the oil is spread evenly throughout the ocean.  Suppose the oil were confined to a layer 1m thick.  In this case, the oil would cover 0.07 square km.  This would be like covering 7.6 Fenway Parks with 1m of oil.  Again, doesn't seem like much, especially if you're a Yankee fan.  The problem, though is that reality is somewhere in between the "completely mixed" or "pure oil" alternatives.  

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One of the things that struck me about the comments from BP, is that the oil slick can be seen from space.  In my opinion, anything that can be seen from space is probably not small.  Roffer's Ocean Fishing Forecasting Service is issuing regular updates on the position of the oil slick using regular satellite images.  By my crude counting of the "oily" squares in their latest images, the oil slick now covers 135,531 square km.  If we assume that the slick is 10m deep, then the slick is about a 0.000005% oil-water mixture.  To me, this provides a rough guideline for the concentration of oil necessary to cause some effect (or at least, to make the water look oily).  Using these numbers, the slick now covers 8.5% of the surface area of the Gulf of Mexico and 0.005% of its total volume.  To put this in a more local perspective, if the slick were in the Gulf of Maine, it would cover 72% of the surface and affect 5% of its volume.  Sounds like a big deal to me.

Sources:
volumes & surfaces areas of World Ocean and Gulf of Mexico--wikipedia
flow rates of oil--New York Times

Red tide photogrammetry in Mexico

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Just a quick note on our sea surface monitoring project. We are working with a group in Ensenada, Mexico to apply our camera system (designed for oil spill mitigation) to a red tide monitoring project. The images below show a dry run, so there is no red tide present, but stay tuned. If this project gets off the ground, it would be a neat application of our system.


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Original photo

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Georectified photo

The ground control points (x's and o's) are just eyeballed in this rectification, so there is noticeable error, particularly with the middle point.  This is something I hope to improve upon.  Also, we hope to cover more area with multiple cameras.

Live "Gull's Eye" Camera

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As part of my ocean photogrammetry project, I've installed a live camera taking time lapse photography of Portland Harbor.  The objective here is to test a low-cost live monitoring system for surface slicks (i.e. oil).  The images can be georectified on the fly, giving a latitude-longitude position of everything we can see on the surface of the water (see image).

Right now, I've set the website up to show the last twenty minutes of images in an animation.  The next step is to show an animation of the rectified images along side the original.  Stay tuned for this exciting update.

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Georectified photographs of Portland Harbor. This figure shows two photos taken
from different angles, overlaid on the same portion of the harbor.


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Image from the live Gull's Eye camera.  Click here for animation of current images.

Airplane photo update

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Couldn't help playing a bit with one of the airplane photos from the previous entry.  Thepicture below (left) shows a series of vortices trailing off of the upper edge of the island.  The vortices were hard to see when the plane was just above them, but they really jumped out when the moved into the sun glint.  While you can see them in the raw photo, a little work in Matlab highlights the vortices (image on the right).  To get this image, I made a black & white version of the image.  I then created a smoothed version (median smoother with a radius of 5 pixels).  The smoothed version removes the fine scale features we're interested in, leaving only large-scale continuous features like the island and the sun.  I then subtracted the smoothed version from the raw, to create an anomaly.  I then squared the anomaly (to make the large differences pop) and multiplied by the sign of the anomaly (so that +/- were retained).  Finally, I replaced values close to zero (absolute value <5) with nans and then overlayed on to the photo.  So, the vortices highlighted in red are reflecting more light than expected (sea surface angled towards the camera or smoother water), and those in blue are reflecting less light than expected (rougher water?). 

slickprocess.jpg

Oceanographer on an airplane

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One of the perks of my job is getting to visit cool places.  Of course, Hawaii is my all time favorite (three Ocean Sciences conferences), with Copenhagen (ASLO Meeting) and Aquafredda (Italy, NATO summer institute) also meriting consideration.  Worst business travel experience: Orlando (Ocean Science conference).  My guess is that hell looks a lot like International Dr. in Orlando, with the Orlando-Orange County Civic Center containing the 8th and 9th circles. 

Most of the time, I'm pretty busy at these conferences and don't have a lot of time to sightsee.  Still, travel always presents something new and different.  For example, last week, I attended the GLOBEC Open Sciences Meeting in Victoria, BC Canada.  Beautiful town, nice hotel, nice conference center, and interesting meeting.  The only disappointment was not getting a chance to go diving or hiking.  However, just flying in the Northwest is fun, and scientifically interesting. On my flight to Seattle, we flew over the San Juan Islands (I think).  There was a bit of wind, enough to give the ocean's surface some texture, but not enough to make white caps.  Ideal conditions for observing physical oceanography from space.  While taking off from Vancouver, I could see thin (few meters wide) bands of smooth water--almost certainly Langmuir cells. The smooth water indicates a convergence zone, with oils on the surface of the water (mostly from algae) damping out the waves at the convergence.  Unfortunately, airline safety rules didn't allow for photos during takeoff.  As we leveled off, I could see larger areas of smooth waters trailing off of the islands.  My guess is that these are ribbons of algal-oils being swept off the shore.  One thing I was fascinated by was how the surface features changed if you looked into the sun glint.  For example, the picture below shows a series of vortices trailing off of the upper edge of the island at the center of the photo (the one that looks suspiciously like a sideways "X" chromosome).

slick1.jpg

Another non-oceanographic example is the propeller in the photo below.  While taking a photo of the Olympic Mountains peaking above the clouds, I noticed that the iPhone screen was doing weird things to the planes propeller.  When I took the picture, it looks like the propeller is falling to pieces, with the bits lining up in a regular way.  Still haven't worked out the details exactly, but it is an aliasing between the scan rate the iPhone's CCD camera (exposes pixel by pixel, not all at once) and the rate at which the propeller is spinning.  

prop2.jpg

Sea Surface Time Lapse

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Here is an example of the results of the georectified time lapse photogrammetry.  This is still rough around the edges, but you can see some neat phenomena.  As in the earlier entry, the photo on the right is the original (a bit stretched), and the image on the left is the rectified, top-down version.  This is one day of images, taken once per minute.  Anything on the surface of the water is rectified correctly, but anything with height, such as tankers and buildings, will be skewed.  There are some very coherent and complex marine surface films.  It's also interesting to watch the boat traffic.  We have a really busy harbor.




There is almost a year's worth of data to analyze--that's one image per minute, every day--so I've got my work cut out for me.  We can use the movement of the surface films to infer flow velocities, and examine these under different wind and tidal regimes.

Just a quick note: marine surface films are generally not the result of spilled oil.  They are caused by oils generated by living organisms in the ocean.

Gull's Eye View

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Lots of scientists look forward to analyzing the data they've collected.  This can be one of the most exciting stages of the scientific method because you start to answer some of the questions you've posed.

For me, the data collection itself can be just as fun.

One of the perks of having cameras that capture images every minute is that we capture many of the beautiful phenomena that take place on the ocean.  As long as they take place on time scales longer than one minute, and as long as they happen when it's not dark out, I'll catch a photo.

The first image shows sea smoke, which seems to happen on a bitterly cold day each year around this time.  When the temperature of the water is warmer than that of the air, and the water evaporates faster than the air can absorb it, the excess water condenses into the smoky apparition that we see.  As long as the temperature conditions are just right, these foggy conditions will persist long enough for us to enjoy the spectacle.


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The next image shows some broken ice floating downstream and out of the harbor.  Over the course of the winter, we see a lot of different types of ice on the surface of the harbor.  Some forms originate upstream while others form along the edges of the water.  Taking the time to look at these images and explore the harbor helps to build an intuition about the environment.  To me, it's important to do this before jumping in to the analysis of the data.  I find that taking the time to do this helps me build insight no matter what project I'm working on.

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Sea Surface Photogrammetry

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The image below shows how photography of the sea surface can be used to map surface features.  The photo in the upper right hand corner was taken from the control booth on the Casco Bay Bridge in Portland, Maine.  The image on the left is the georectification of the same photo, superimposed on an aerial image of the harbor.  Using this technique, combined with time-lapse photography, we can study the dynamics of the fluid in the harbor.  We can also trace the movement of visible phenomena, such as sea ice or biogenic oil.
CascoBayBridge01.jpg

We have collected many months of time-lapse photography of the sea surface, mostly in Portland Harbor.  Our system typically takes a photo once per minute.  We will discuss our results in later entries, and include some cool animations.

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