My Ten Cents: #Congress_2013 - Day 2, 28 May

Still enjoying Saskatoon, the 'Paris of the Prairies', attending the joint meeting of the Canadian Water Resources Association, the Canadian Geophysical Union, and the Canadian Meteorological and Oceanograhic Society. It's officially the 2013 Joint Scientific Congress and is the first time the three societies have met together. 

Yesterday I posted the highlights of Day 1; today it's Day 2. I'll once again focus on the plenary speakers.We had no politicians today, so we got right down to science.

I am unsure whether plenary and other presentations will be posted on the meeting's WWW site. You might want to check in a week or so. 

First up was Dr. W. Richard 'Dick' Peltier of the University of Toronto. His topic was 'The Thermohaline Circulation of the Oceans: Impacts on Climate Variability and Change':

Although the wind driven circulation of the oceans is reasonably well understood, the same cannot to claimed for the thermohaline circulation (THC). In part this is a consequence of the fact that the timescales of the variability associated with it, both forced and internal, tend to be multi-decadal or longer. I will review what is known concerning THC variability and its role in long timescale climate change from both a transient forced perspective and from the perspective of its statistical equilibrium strength under fixed boundary conditions that differ radically from modern.

Under modern climate conditions there exists clear evidence that the THC is deeply involved in the so-called Atlantic Multi-decadal Oscillation (AMO). Under Last Glacial Maximum (LGM) boundary conditions there is also evidence, based upon the Pa/Th tracer of the overturning strength, that the North Atlantic Deep Water (NADW) cell was about 40 % weaker than modern. During the last glacial-interglacial transition, recent research has established that the famous-Younger Dryas (YD) hemispheric cooling event was forced by a massive flood of fresh water out onto the surface of the Arctic Ocean through the Mackenzie River outlet and to the subsequent slow down of the THC that this "water-hosing" event produced. Modern coupled atmosphere-ocean climate models are able to successfully explain the related observational constraints, a fact that should be construed to provide a useful test of the models that we employ to make global warming projections when these models are asked to perform under conditions to which they have not been tuned. A fundamental issue concerning the ocean component of these models continues to be the representations they employ of diapycnal turbulent diffusivity. Recent results concerning this process that appear to be important to understanding how ventilated polar waters return to shallower depth, often in the opposite hemisphere, will be reviewed.

As an ersatz fluid dynamicist I have always been fascinated by THC ever since I heard Wallace S. 'Wally' Broecker speak on this topic almost 22 years ago. He addressed the issue of the shutdown or weakening of the North Atlantic THC that keeps northern Europe from becoming an icebox. Kind of scary. Broecker concluded his talk with today's quote. I have never forgotten it, nor the original drawing he used to illustrate it. 

Peltier did nothing to allay my concerns in his excellent talk. He alluded to an 'iceberg armada' from the eastern margin of the Laurentide ice sheet that freshened the North Atlantic and weakened the THC near the end of the LGM. Ooops!

The Younger Dryas cold reversal was caused by the separation of the Cordilleran and Laurentide ice sheets, leaving a pathway for freshwater drainage northward through the Mackenzie basin, freshening the Arctic Ocean and slowing down the THC. Prior to the ice sheet separation, freshwater drainage was south down the Mississippi Valley.

An excellent presentation.

And here is something else about the Arctic Ocean: The Arctic Ice “Death Spiral” http://is.gd/yrR1mL 

The second speaker was Dr. Robie MacDonald, an oceanographic geochemist at the Institute of Ocean Sciences, Department of Fisheries and Oceans.  He spoke on 'Seasonal Ice in the Arctic Ocean is Vanishing – So, What Else is New?' No, it's not the trite topic you'd think: 

It has become clear in my lifetime that summer sea ice in the Arctic Ocean will become a thing of the past, probably within decades. The evidence for this, collected by satellite images and under-the-ice nuclear submarine missions, is stunningly clear: each year seems to hold another record low in ice cover, further still below the projections of the most pessimistic models. But when you seek evidence for other system changes, the data base thins very quickly with the result that biological and geochemical changes likely to manifest themselves in the new Arctic Ocean are mostly a matter for speculation based partly on paleo records and partly on incomplete understanding of how ice controls biogeochemical cycles. The void in coherent biogeochemical time series does not help. I will present my “geochemical” view from studying freshwater, organic carbon and contaminant tracers to propose how the cycles of these components will change in the Arctic Ocean as a consequence of the shift from multi-year permanent pack ice, to first-year seasonal ice. 

Unlike the first talk, about which I knew something, the topic of this talk was quite new to me - the details, at least. I found it fascinating. 

Most of the seasonal sea ice is being lost on the Pacific side of the Arctic Ocean - contrary to predictions made years ago. In 1979, the volume of multiyear ice was 16,855 cubic kilometers; in 2012 it was 3,261 cubic kilometers. And that sea ice is not just cover, it is habitat. Ooops! 

So what does this mean, that much of the multiyear ice is becoming first year ice? Try these: 1) fresh, thick ice to salty, thin ice; 2) greater brine production engine; 3) snow cover change; 4) light penetration change; 5) biological productivity change; and 6) habitat change.

MacDonald noted that total freshwater runoff to the Arctic Ocean is about 2,500 cubic kilometers per year. This runoff and sea ice melting mean that there will be about a 0.6m sea level rise by 2100, creating more shelf. The decrease in ice cover will mean more coastal erosion, becuase the winds will be blowing across more open water than ice cover. He also posited that because of the change in acidity in the Arctic Ocean it might be intolerant to aragonite by 2100. That would be anathema to those organisms building aragonite (calcium carbonate) shells.

He also discussed the three different kinds of shelves in the Arctic basin: inflow; interior, and outfow.

MacDonald also discussed the four kinds of Arctic Ocean pumps: 1) biological (soft parts); 2) carbonate (hard parts); 3) solubility; and 4) shelf (strongest). The latter two are the most significant. How do the pumps respond to change? Can we monitor pumps? 

So what are the important points/questions? Here goes: 1) paleo records are of little help in the Arctic Ocean system; 2) light or nutrient limited? 3) freshwater storage (ice melt); 4) shelves and basins are different; 5) export vs. recycling?

And a few  more...How does change in sea ice affect freshwater storage? How does the change in sea ice from multiyear to first year ice affect biogeochemical cycling in the ice shelf and ocean? 

My brain got a workout. Two excellent talks.

And I had a great time at the CWRA awards luncheon. Wonderful bunch of folks. I am looking forward to collaboration between AWRA and CWRA.

"The climate system is an angry beast, and we are poking at it with sticks." -- Wallace S. Broecker, Albuquerque, NM, c. 1991

Comments

[geohydro2011]

Saw your tweet re WaterWired Darcy Bushnell's report on litigation entitled Texas v New Mexico and Colorado is.gd/7OhQE7. If I were New Mexico, I would do what was done by a groundwater irrigation district in Idaho a few years back being sued by surface water irrigators for over pumping and depleting surface water flow; I'd acquire satellite imagery (NDVI) or scenes from the areas supposedly affected, scenes typically acquired during the growing season. If NM is green and lush whereas TX is brown and dry and they get water from the same source, maybe there is a problem. But if both NM and TX and especially TX are green NDVI-wise, how can TX show injury due to NM's supposed actions? Indeed, if NM is brown and TX is green and they both get water from the same source, I would have a hard time finding that NM was the problem. In the Idaho case, the satellite imagery showed no injury to the surface water irrigators--their fields were green. But in my mind, Texas groundwater policy encourages groundwater mining or at least encourages pumping water in a manner similar to pumping oil seemingly without an understanding of the intimate connection between surface- and ground-water--that seems to be as big if not a bigger problem here.

[geohydro2011]

I think, and I have nothing but my gut to back me up, but I think that as we learn more about changes in Arctic Ocean sea ice and subsequent effects upon thermohaline circulation that we'll find that we'll have to consider how biota figure into the equations. That's just my hunch. But I say this as I recall in many of the water related research questions, the emphasis was on modeling physical processes with nary a thought of how biota affect the systems (such as the Leopold and Maddock's equations of hydraulic geometry or Jenkin's equation dealing with groundwater pumping). I think it was Boone Kauffman that told me once that there was as much living material buried under and associated with a tree as exists above the soil of that same tree (e.g., a mirror image, I imagine, of a tree with the land surface serving as the plane the tree is reflected across). As I thought about Boone's claim, I couldn't help but think what effects that not only roots, but also bacteria and fungi were having on water balance. And today we find very fine OSU research into Brook's "two water worlds" phenomenon driven by roots hanging onto water in some forests. Thus in a similar vein, as the Arctic Ocean sea ice dissolves I can't but help wonder what effect the blooms of phytoplankton and other biota (even viruses) will have on the thermohaline circulation. Maybe no effect. But then again, well, it will be interesting to say the least. Thanks for sharing your observations in Saskatoon--thought provoking.