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This is your ocean under global warming


Video: Rob’s kitchen demonstration of the wine-dark sea in a pint glass. 

We all know communities that believe their children are better than average. Lately, I’ve been startled to hear conservation colleagues down by the Gulf of Maine, in Boston, Portsmouth and Portland, say their ocean water is special because it’s warming faster due to climate change than seawater anywhere else. They think their sea is more troubled than others, and this time no one is talking fishing.

Local concerns for miscreant seawaters began with the report of a respectable science journal in 2015. The piece had been picked up by media outlets with much to do about the implications, consequences, and what to blame.  The article boiled down to two sentences. “Between 2004 and 2013, the mean surface temperature of the Gulf of Maine rose a remarkable 4 degrees (Fahrenheit).”  Last year’s “rise in temperature exceeded those found in 99 percent of the world’s other large bodies of saltwater.”

People are welcome to their beliefs and if it leads to more responsible actions so much the better.  My interest was piqued in November when I went on a whale watch out of Boston and later to a science café in Portsmouth.

The whale watch narrator explained global warming is like a blanket of greenhouse gasses on the water, warming it.   What she did not say explicitly but inferred, is that this bit of ocean is warming faster because it’s got a thicker climate change blanket on it.  I got an image of the world wrapped in a quilt of patches of varying thicknesses, and unfortunately we got a thick patch.

Climate Change is not place specific; it’s global.  The winds blow around the world because the world is spinning.  So some of the air we breathe today was air in China 3 to 6 months ago.  The climate change blanket is of one thickness everywhere.  It does not bunch up like your comforter at the end of the bed to warm your feet more than your shoulders.  Instead, as the amount greenhouse gasses in the atmosphere goes up the climate change blanket thickens uniformly.

At the science café in a pub with less than a pint inside me, a marine biology doctoral student explained why rising surface water temperatures are a concern for lobsters and bottom dwelling demersal fish (cod, haddock, halibut and hake). He said that they could correlate surface water temperature with the temperatures of water deeper down.

I did not challenge their assumptions of ocean dynamics.  Instead I came up with an experiment to demonstrate how important surface waters are to the health of ocean ecosystems. In my kitchen, I got out a measured pint glass. I poured some old wine up to the 12-ounce line to represent the wine-dark sea.  I added a level tablespoon of salt to bring the salinity to about 40 parts per thousand or 4% salt, thinking I would create Homer’s sea. I stirred with a long handled spoon.  Later I found much salt still crystallized on the bottom, so perhaps this was closer to Gulf of Maine seawater at 34 parts per thousand.

I poured tap water from a small pitcher onto a spoon so as not to disturb the waters.  I filled it to the brim, the full 16 ounces.  There was some mixing because the top water took on a pinkish color.

For Global Warming I turned on a hair dryer and held it close to the pint glass.  It made the surface ripple.  I turned my cell phone’s video recorder on and watched the distinct boundary layer, the thermocline, where the water turned from pink to red.   I watched the 12-ounce mark and saw no mixing of surface and deep water.  After a couple of minutes, I turned the hair dryer off.

Energy as heat from the hair dryer had gone into the pink sea surface layer.  Yet, there was no mixing into the deep waters.  Hot air and warming surface waters had no effect on the vast waters below.  Had there been a crayfish at the bottom of my pint glass, it would have felt no change in conditions when the hair dryer was on.   This is good news for lobsters and cod living on the ocean floor.

The reason researchers found surface water temperatures differing from one year to the next, and needed to find a medium, like an average temperature, before looking for trends is because surface water temperature is determined by how hot or cold the water was when entering the sea.  It is also effected by air temperatures because it has so little depth and so much area in contact with the air, like a lens on the water.  No surprise, surface waters are warmer in the summer, colder in the winter.  Their temperatures swing with the seasons.

The science article failed to give context of how much surface waters varied year to year.  It did not present surface water temperatures for the other three seasons or give salinity values, needed to determine density and to identify water bodies.

The surface water temperatures of the Gulf of Maine have always varied more widely than Atlantic Ocean temperatures because the Gulf is an estuary.  Rivers flowing into the Gulf make it more fresh.  Surface waters in the Gulf are 34 parts per thousand salt.  In the Atlantic Ocean beyond Georges Banks the salinity is 36 parts per thousand salt.

There are four bodies of water in the Gulf of Maine, each with a distinguishing temperature and salinity that separates the water bodies.  At the greatest depths is a swirl of Slope Water and Labrador Current Water.  Imagine fudge ripple.  Above is a layer of Shelf Water, that flows over Georges and Browns Bank.  Finally surface waters are at the very top of the water column.  That change in temperature of the surface water, be it as many as 4 degrees Farenheight, will be absorbed by the adjacent Shelf Water.  Because it has so much volume Shelf Water temperature is not likely to change.  Instead the boundary layer, the thermocline, will rise reducing the volume, indicated by depth, of surface water. 

The “rise in temperature exceeded those found in 99 percent of the world’s other large bodies of saltwater.”  One reasons for this extraordinary finding is that nowhere else are the weather-fickle vagrancies of surface water temperatures considered relevant to large bodies of saltwater.  Oceanographers, lobsters, cod and many others are not concerned with the water temperature of the top 1% during only the summer because the Gulf of Maine is very deep.

On Georges Bank, the southern limit of cod, where there is no underlying Slope Water and Labrador Current Water, only Shelf Water and little surface water buffering Shelf Water from weather, here there is reason for concern of Global Warming having an impact in shallow waters.  Not so much in the deep swirling waters of the Gulf of Maine.

3 responses on “This is your ocean under global warming

  1. Rob Moir, Ph.D. Post author

    Ryan, Good point. The four degrees increase was from the Science article. It was not obvious to me whether it was centigrade or Fahrenheit. Centigrade would be greater increase, that seems unlikely. But than surface waters may fluctuate weekly quite widely. Canadian Broadcasting Co reported that the 4 degree increase was Fahrenheit.

  2. Dr. Robert A. Cospito

    A temperature of 2 degrees would have a catastrophic effect that’s incredulous to comprehend but it would completely obliterate lower Manhattan by submerging the entire area. Rising temperatures are playing havoc with many species of wildlife such as the Polar Bears. Of course the “capitalists” will say otherwise!!!
    – Dr. Robert A. Cospito.

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