January 2014 Archives

The Gulf of Maine is Warming Fast!

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I'm at the NCSE "Climate Solutions Conference" in Washington, DC this week.  I was invited to talk about the lessons we can learn from the 2012 ocean heat wave in a session on "Managing Fisheries Under Climate Change."  For my talk, I was curious whether the warming we've seen in the Gulf of Maine is unique.  Short answers: it is very unique: since 2004, the Gulf of Maine has warmed faster than 99.85% of the global ocean.


To get to this number, I grabbed the global sea surface temperature (SST) data set from NOAA's   optimally interpolated product.  I removed the mean annual cycle (1982-2011) to produce daily anomalies.  I then selected 2,000 point at random (shown over the mean SST from June):
SSTtrendpoints.jpg
At each point, I computed the linear trend over the last 10 years (January 2004-September 2013).  At this relatively short time scale, I would expect to see a lot of variability--a lot of places warming, but also a lot of places cooling, and this is what I found. The mean trend is 0.006°C/yr and there are slightly more points that are warming (1024 points) than cooling (976).  

The distribution of trends is pretty much normal (in the statistical sense):
GlobalSSTdistr.jpg
but the Gulf of Maine is decidedly abnormal.  The Gulf is warming at 0.23°C/yr (see my previous post), and from my 2000 randomly selected points, I found only four (FOUR!) that were warming faster (red stars on the map).    Turns out one of them was from the Gulf of Maine (go figure), and that the other points were from the Kuroshio extension region northeast of Japan.  This makes some sense oceanographically and is probably driven by a northward shift in the Kuroshio (the Pacific's Gulf Stream). 

According to this analysis, the warming in the Gulf is remarkable, and frankly, a little scary.  However, it is important to remember that this is just a statistical analysis.  At some point, the trend will slow, but we don't know when and by how much.  There is clearly more work to be done to understand the mechanisms that are driving the current trend.   And, there is also an opportunity to use the Gulf of Maine to understand how an ecosystem responds to rapid climate change.

Are chaetognaths gelatinous? You be the judge

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(Apologies in advance for the perhaps obscure and esoteric content of this entry.)

The "Jelly Ocean Hypothesis" suggests that due to human-driven changes in the environment, we are headed toward an ocean dominated by jellyfish. Before determining whether this scientifically intriguing dystopian nightmare comes to pass, we need to agree on what classifies as a "gelatinous zooplankton"

Some people assert that chaetognaths fit into this category; others do not. Since we are debating this in the lab now, here is some information for context. What we need is a measure of how gelatinous something is. Ideally we would like to have a measure of carbon-to-volume ratio for each taxon--basically a measure of organic density--but for now, dry weight as a percentage of wet weight (DW as %WW) will have to do. --Basically the amount of the organism that is not water.

Ctenophore01.jpg Calanus_CV.jpg 170px-MEB_back.png
ctenophore    copepod            chaetognath
gelatinous    not gelatinous       ??


Here are the numbers:

Euphausiid DW as %WW: range 20-24% (depending on stage) +/- ~3
(Iguchi & Ikeda 1998 table 1)

Copepod DW as %WW: average ~19% +/- 10
(computed from Mauchline 1998 fig 50)

Chaetognath DW as % WW: 8
(Sameoto 1972 reported in Feigenbaum 1982)

Thaliacea DW as %WW: average 5.5% +/- 2.47
Ctenophora DW as %WW: average 3.53% +/- 0.92
Cnidaria DW as % WW: average 4.07% +/- 1.23
(Lucas et al. 2011)

And in graphical format:

chaetognath1.jpg
<--------- more gelatinous                                       less gelatinous --------->


I think this crude and cursory analysis settles the debate. Now we can get back to talking about copepods.

Nick Record, signing off

References

Lucas CH, Pitt KA, Purcell JE, Lebrato M, Condon RH (2011) What's in a jellyfish? Proximate and elemental composition and biometric relationships for use in biogeochemical studies. Ecology 92:1704.

Feigenbaum D (1982) Feeding by the chaetognath, Sagitta elegans, at low temperatures in Vineyard Sound, Massachusetts. Limnol. Oceanogr. 27(4): 699-706.

Iguchi N, Ikeda T (1998) Elemental composition (C, H, N) of the euphausiid Euphausia pacifica in Toyama Bay, southern Japan Sea. Plankton Biol. Ecol. 45(1): 79-84.

Mauchline (1998) The biology of calanoid copepods

Sameoto DD (1972) Yearly respiration rate and estimated energy budget for Sagittu elegans. J. Fish. Res. Bd. Can. 29: 987-996.

Gulf of Maine Temperature Trends

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Happy 2014 to you, dear Seascape reader(s)! To kick off another year of oceanographic musings, here is the updated temperature trend for the Gulf of Maine:

GOMssttimeseries.jpg

This is essentially the same figure we used to show the 2012 event, but extended through early September (the last available AVHRR OI field).  As you can see, 2013 was cooler than 2012, but was still a very warm year. The recent warming trend has continued (it's actually a little stronger), and 2012 still stands out as unusual.  Of course, this doesn't include the impact of a few very cold days recently (I'm talking about you, polar vortex), nor does it include the very mild weather we're experiencing now.  Temperatures in the ocean change much more slowly than those on land, and water temperatures are a better indicator of climate trends than the weather on a given day.  I hope to update the SST animations in a couple of weeks.

 

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This page is an archive of entries from January 2014 listed from newest to oldest.

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