Modeling the Whale Pump

Trying to model the whale pump will probably be horribly complex but for all of that, very worthwhile to do.  It could effect the fisheries of the world and the policies we adopt.  So what is the Whale Pump.

Many whales feed in deep water and defecate and excrete (pee) in surface waters.  They are pumping nutrients from deep dark waters into the photic zone where algae, utilizing the energy from the sun, can  rebuild these mineralized compounds back into energy rich fats, proteins etc.  Many whales also feed on the surface and equally, defecate on the surface, circulating nutrients to power the web of life.  I don't know where to start so I'll just plunge in, in the middle and see where we get to.

Let's suppose we are in the Antarctic and, for the sake of the argument, that the upwhelling that occurs there is bringing up all the nutrients needed.  Nutrients are not  limiting  primary production and hence not limiting secondary, tertiary etc. production.  A bunch of whales now add their nutrients to the photic zone.   We are already at the sun limit (all the primary production that the sun can power is already taking place) so primary production does not increase.  That is the "first approximation" but here comes the first wrinkle.

Some algae can use more complex molecules such as amino acids in addition to the fully mineralized nutrients such as nitrates, phosphates and all the other 'ates' they require.   In a previous blog, I discuss the detritus cycle. In the detritus cycle bacteria which secrete the enzyme, cellulase use the chemical energy from the cellulose rather than sun energy to build their bodies.  This forms the base of a food chain that is independent of sun light.  It is likely that the algae which can utilize amino acids and perhaps a range of other energy rich compounds also get at least part of their energy from these energy rich molecules.  Here we have a likely way around the limit to primary productivity set by the sun.  Whale poo is likely to be rich in such compounds.  Lets  look now at what primary productivity we could expect from whale poo in water which has less than adequate nutrients.

If you were to make a first approximation of the effect of Whale Poo, you might say that the amount of nutrient given out by the whales could support X amount of primary productivity (algae), 0.1X of secondary productivity (krill), and 0.01X of tertiary productivity (penguin)* and so on up the food chain.  However it is not that simple.  Each tropic layer, including the algae, is excreting into the water and providing nutrients for the sun to build back into more energetic compounds.  The actions of all these organisms act to lock nutrients in the surface sunlit waters and they are only slowly  lost to deep water.

*Note that about 10% of the substance (or energy if you like) from one tropic layer is transferred to the next layer.

So already, the situation is complicated.  How about when the whales migrate to oligotrophic (nutrient poor) waters.  A number of whale species migrate to the Gulf of California and other nutrient poor tropical waters to give birth to their young.  Once the Colorado river flowed into the head of this semi confined body of water.  It undoubtedly carried masses of nutrients in the form of dissolved and particulate material.  This flow has almost ceased as water extraction has increased for agriculture.  Into this sheltered water adult female whales migrate and give birth to their young. Even if the adults do not feed and therefore, do not defecate, they suckle their young and the young poop out nutrients.  If they are similar to most animals, 90% of the nutrients the young consume as milk are pooped out into the water.  Since whales are probably down to one or two percent of the population* that  existed at before the advent of whaling, you can imagine the reduction in nutrients and the potential if whales returned to their original abundance.  The Gulf of California is surrounded by desert.  It has a large number of sun hours and so the potential primary productivity is great if nutrients are made available**.

 *This site gives the population of Right Whales in 1997 compared with the historical estimates and includes the rate of growth of the population.  If you invert the growth rate and project it back to the end of industrial whaling, you realize that this species was very close to extinction when whaling ceased.

A well known migration of whales are the Humpbacks of the Southern ocean.  They migrate from the Antarctic to the warm waters of various south sea islands via New Zealand waters to give birth.  There is no food  for the adult females in the tropics (New Zealand Geographic, Jan-Feb 2013 p36) but they have gorged on two tons of krill a day over the Antarctic winter and now feed their young 200l of rich milk per day.  Nutrients are being shifted from Antarctic waters to tropical waters and as we have seen, these nutrients cycle around in surface sunlit waters only slowly being sequestered in deep water.  A little nutrient goes a long way in nutrient poor areas.  Imagine what sort of fisheries could result from whale populations restored to their former levels.

Hopefully, this sort of argument might convince the remaining few whaling countries to cease killing whales.  These same nations are also fishing nations and are reducing their own fish catches by killing whales.

Rapid Arctic Freeze

Climate change deniers are taking great encouragement from the rapid increase in ice extent following the Sept15, 2012 record low ice cover in the Arctic ocean.  Not so fast guys.  This is just about what one would expect.

Heat moves by three basic physics phenomenon.  One is radiation.  This is how we get our heat from the sun.  The sun gives out masses of electro-magnetic energy and we intercept a small portion of it.  Some of it is absorbed by earth materials and converted into heat.  Depending on the temperature of the source, large amounts of heat can be transferred by radiation.

The second is convection or 'mass transfer'  This is by far the strongest of the three.  A heat pipe is a good example of a device using convection to transfer massive amount of heat.  A little closer to home, you have a furnace in your basement.  It heats air which is transferred to upper rooms through ducting with cold air returning to the furnace by other ducting.  Huge amounts of heat can be transferred this way.

The third and weakest is conduction and this is the one that concerns us here.  On one side of a material is a source of heat which sets the atoms in the material vibrating.  They pass on the vibrations (heat) to the adjacent molecules and so forth until the heat reaches the other side and heats up whatever is on the cold side of the material.  Even with such good conductors as silver and copper, the amount of heat transferred compared to, say, a heat pipe that uses convection, to transfer heat, is tiny.  In an insulator such as ice, heat transfer is indeed minuscule.

As a mind exercise, consider a time, say, during the little ice age which froze the Thames River.  On Sept 15, the Arctic ocean was probably completely covered with ice.  As the sun left the Arctic and the air temperature plunged to minus 50 degrees, there was a temperature gradient across the ice from minus one or two degrees (the lowest temperature at which sea water is liquid) to minus 50 in the air;  A great temperature gradient to help heat escape from the sea but a thick layer of ice is slowing down the flow of heat.  Of course to freeze more ice on to the bottom of the floating ice, heat has to escape by conduction.

Now consider the present situation.  Well over half of the Arctic was ice free on Sept 15 2012 and the rest of the ocean was covered with much thinner ice than in previous years.  The sun leaves the Arctic and the freeze commences.  Even after there is a complete ice cover, the ice is far thinner than in previous times so there is more heat transfer.  Remember that heat transfer under the influence of a given delta T across a substance is inversely proportional to the thickness of the substance.  Of course as the ice gets thicker, heat transfer slows.  There are a few other little wrinkles in the story.

As water freezes, it gives out 80cal of heat per gram which tends to keep the air over the Arctic warmer.  The freezing water is "trying" to keep the temperature at zero.  Of course this reduces the temperature gradient across the ice and reduces freezing.  Not to take too much comfort from the fast freeze, though.  Consider a time in the future when the Arctic becomes ice free in, say, June.

Now the Arctic ocean can really begin to accumulate heat.  Not only is the whole surface of the ocean turned into a giant solar collector but there is no ice to keep the water cool as it melts.  worse still, hurricanes, such as the one we saw on Aug 6 ff, 2012 are much more likely and will mix deep and shallow water, storing up great amounts of heat in the depth of the Arctic ocean.  Incidentally, there is a huge heat store in the deep water of the Arctic ocean already, kept there by a salinity gradient.  Without the melting of ice freshening the surface water, storms of a given magnitude will cause much greater mixing than when there was a strong density gradient.

This may explain fossil records of a much warmer Arctic Ocean even though the ocean was at the North pole when the fossils were laid down.  We could be heading for a totally unrecognizable climate regime in the not too distant future.

Just one last comment.  No fun if you don't put your whatsit on the block.  We are nearing the peak of a fairly weak solar maximum and it will probably arrive next year.  This means that the small effect of the solar cycles will be greater than last year.  It also appears (dec14, 2012) that we are heading into an El Nino.  This is also said to increase warming in the Arctic.  Now, of course, these weather phenomenon seem to be subject to random (another word for "we don't yet understand them") variations but it seems very likely that 2013 will break this year's record low ice extent.  We will just have to wait and see*.

*Note, the ice extent returned to the trend line in 2013 and looks to be about to do the same in 2014.  No El Nino occurred and ice extent did not drop down in an exceptional manner.