November 2011 Archives

Atlantic salmon migration

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First off, let me introduce myself.  I'm Pam, I've been a GMRI intern for the last 5 months or so and have been lucky enough to be part of the salmon team here.  It's been a great experience and I've definitely learned a lot! 

 

There's a couple of salmon-related projects going on at GMRI, I've been involved with work studying Atlantic salmon migration in the Gulf of Maine.  In the Gulf of Maine, salmon begin their migration when they enter the marine environment.  This initial migration phase occurs as they move through the Gulf of Maine to the coast of Nova Scotia by Halifax (they then continue all the way up to Greenland).  However, we don't know where in the Gulf of Maine the salmon are moving through, how they're finding their way through or how the variability in the Gulf of Maine physical environment (currents and temperatures) affects them.  I've spent the last several months trying to address these questions using what's known as "individual-based modeling" (IBM).

 

IBMs let us simulate individual fish.  We can give the fish different sets of rules to define their behavior.  This is neat because it lets us experiment with different orientation methods to see what methods might be plausible and lets us simulate the path an individual fish follows through the Gulf of Maine.  Then by using physical conditions from different years, we can see how these paths change due to differences in temperatures and currents. 



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This figure shows simulated tracks for fish- each red line is a different fish.  For this figure, the fish were instructed to swim in the direction the current was flowing.


As it turns out, the salmon are affected by interannual variability in their environment.  In general, stronger currents result in fewer salmon successfully navigating their way through the Gulf of Maine.  However, the degree to which changes in currents affect salmon depends on how salmon orient for migration.  If salmon use directed swimming (know the direction they want to go and try to swim in that direction), then changes in currents do not have that large of an impact.  However, if salmon use other behaviors (such as using temperatures and/or currents to navigate), then changes in currents do have a larger impact.  Also, while we have no way right now of concluding what behavior salmon do use to orient, we can rule out a couple of possibilities.  Based on the lack of success (i.e. no fish make it to Halifax), we know that the salmon aren't passively drifting and aren't simply swimming in the opposite direction of the currents.  

Painting Monets

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The concept for this entry comes from a presentation by Jeffrey Runge.  While practicing a talk at GMRI in front of a small audience, Jeff brought up an interesting analogy for modeling.  He explained that modeling is like impressionistic painting.

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There are many ways to interpret the past and the future.  Models (whether ecosystem, population dynamics, or couple natural and human interactions) are an attempt to portray past time periods and predict future ones.  Jeff describes models with, "Their predictions will not be precise, but more like impressions, but with enough information to discern whether the future state is like a sunny day on the seascoast or a smoggy day in an industrial harbor."  I thought it was a very cool way of describing what a lot of us are working toward.  Beautiful!


The press has been abuzz lately with the Berkley Earth project.

Their recent scientific achievements "confirmed" the warming trend in global temperatures.I admit, there is certainly an amusing irony in the fact that they were partially funded by oil billionaires, but other than that, the climate story hasn't really changed.  At least three groups (NOAA, NASA, HadCRU) had already published the warming trend that the Berkley group found, and it has been studied in detail for decades. 

Sadly, most of us can't make a scientific career out of re-confirming other people's results.  Otherwise, I would just write a paper detailing Einstein's theory of relativity, post it on a really slick website, publish it in a top journal, and rest on my laurels.  After all, relativity has skeptics too.

480px-Einstein_1921_portrait2.jpgWhilst the old-hat temperature trend is making all the headlines, there does appear to be a scientific contribution in the Berkley group's work.  In their first paper, they detail an averaging process that "allows us to include short and discontinuous temperature records."  This is potentially a very useful algorithm.  Earth sciences are riddled with sporadic, truncated, and sparse time series.  If we could use a similar algorithm on other measurements--e.g. salmon returns, copepod abundance, or whale sightings--then we could potentially include data sources that we previously had to omit due to biases.

It's unfortunate that we live in a world where stories about averaging processes don't push paper.

P.S. Hats off to the NOAA scientists who had it right all along.  NOAA gets enough flack about its science already, and is sadly underfunded.  Yet here was a collection of scientists whose main motivation was simply to do good science.

-Nick Record, signing off

My Plan for America and the World

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With the '012 campaign heating up, there are lots plans in the air.  The new craze this year seems to be plans with a strong numerological bent, even if the numerics behind the plans tend towards the vague.  Well, I have a plan of my own.  This is my vision of the future:

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(Yes, I went with a number-based plan, but at least mine is prime.  And patriotically colored.).  Unlike some of the other plans, my plan does not depend on getting past a Senate filibuster, nor does it require an executive order or a super-committee. This plan is already in motion, so strap on your jet pack and come with me to the 3-3-3 future:

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  degrees (C) of warming.  This is the current best estimate for how much warmer air temperatures will be on our planet in 2050 (relative to 2000).  Of course, some places will experience even more warming (take that, Canadian Arctic).  The extra demand for air conditioning should really give a boost to the energy sector.

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  times as many major storm events.  According to the upcoming IPCC report, the intense rainstorms, the kind we normally get once every 20 years, will occur twice every decade.  Numerically inclined readers will note that this is actually a 4-fold increase. I would counter that mine is a conservative plan.  This component of the plan should stimulate the basement sump-pump industry.

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mm/year of sea level rise.  Currently, sea level is rising by 3 mm/year.  3 mm/year times 50 years is 155 mm (15.5 cm), but sea level rise is getting faster and expected to continue to accelerate.  The acceleration is due to the fact that warmer water expands faster when it heated.  The acceleration is also due to increased melting in Greenland and Antarctica.  The ice sheets are the big wild card.  Observations of the last 10 years are more consistent with "fast-ice" scenarios.  By 2050, it is possible we could see 3 decimeters (30cm=1 foot) of rise, although 15-20 cm is more conservative.  This part of the plan should do wonders for stimulating the construction of breakwaters, dikes, and gondolas.

Sources:
IPCC AR4news coverage ofupcoming IPCC special report on "Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation", and Clark et al. 2011.

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