I can't say what the average residence time/ventilation rates in canyons are, but there are some numbers for these things for the specific case of Antarctic Bottom Water in Scotia Sea trenches in http://onlinelibrary.wiley.com/doi/10.1002/grl.50260/abstract

Hope useful...!

Thanks Michael, I am also and old FID Signy 1980 to 83 but limnology. Most of the canyon research expresses the sv flow into and down to indicate that upwelling maybe enhanced to some unknown degree. Nevetheless, any order of magnitude for a deep trench system at this stage good. Another question, can the ventilation rates for ocean intermediate waters that appear to have higher carbon dioxide values working they way up to the surface from the effects of climate change to be used as analogy. In other words can this water dynamics at these similar depths entrain water from trenches

Interesting idea John, but I suspect that the important processes are sufficiently different between intermediate waters and those in canyons that one cannot easily draw a useful quantitative analogy. But maybe someone else in RG world can advise differently! Hope you remember Signy fondly...!

Dear John Gallager,

To get an answer you should narrow down a bit the scope of your question. There are tens of thousands of submarine canyons crossing the continental margins of the world. Peter Harris has listed near 6000 [large] submarine canyons: http://www.sciencedirect.com/science/article/pii/S0025322711001253

Their shapes, depth ranges, lengths, and the oceanographic and sedimentological processes acting on them are very diverse (as well as the inputs of biogenic debris into the canyon or the capacity of the canyon to store that material instead of flushing it further deep...): http://www.annualreviews.org/doi/abs/10.1146/annurev-marine-010213-135037

Furthermore, significant differences in sediment transport/accumulation and circulation patterns can be found not only between different canyons but also from head to mouth of one particular canyon.

Hope this helps…

Regards,

J.M.

Thanks for that, yes I am away of the latest review on submarine canyons and the map of density around the shelf. It s also an artticle with a Gobal persepctive on questioning the other explicit and implicit assumptions associated with the blue carbon conceptal model. In fact a simple global models (or really a stock take), which decibes the average, medium or geometric mean with the uncertainty.

With regards to canyons, Some studies have shown massive amounts of macroalage tranported to theirone local canyon during a singlestorm (up to 1 days north Atlantic primary production).

Neverthelss, I believe there are some common patterns associated with the nature of a canyon instrusion that mayp[roduce typical values across regional scales. For example, a mid water mass cap, increased rates of supply to the bottom by virtue of their intrusion into the shelf from interactions with the local wind shear and so on. I contend it is these common attributes that separate the rest of the shelf deep waters or to indeed short circuits advection in to the deep[er surface waters and to and places where they are no canyons. Therefore, I was hoping to see in the literature a probablitic theory that discribes the typical range of residence times associated and not associated with deep waters of the shelf.

On the other hand are they so individualistic as to have a range of residence times that overlap other deeper areas on and off the shelf. In other words no predictive theory is probably and all states are likely.

I take your important point of variability in deposition. But I think that level of detail is good for the local area for study but in a global context represents may smooth out the extremes if we consider all the exported litter about an instrinsic value. Goodness, this focus, through you answer, is is starting to illustrate the hopelessness of my enquirery already.

What I've done in the submitted article yesterday (and under review) is to just give some examples. e.g. the 260 years within the Gulf of mexico, and to say its unknown but an important question to ask and to test the sequestration potential, as if signifcant raise the value of blue carbon ecosytems srvices considerably. (i,e export arounf 44% of NPP) is assumed to be completely respired.

If you find anything else I would be very grateful

A key parameter in determining ventilation time is the turbulent mixing rate (in both diluting the water in the Canyon and also in reducing its density so that it can be completely flushed out. A major drive of mixing in Canyons is the tide (internal) - the energy transfer is determined not only by the strength of tidal currents but also the local stratification and the slope of the local topography. Given the complexity of these processes I would argue that the ventilation will be very variable. (eg. much like the flushing time of fjords). 

Sigh! your right of course. Indeed I have some experience of ventilation rates in Fjords. My old work in Antarctica for Ellis Fjord  (Hydrobiologia) Vestfold Hills was one extreme I put the age of the bottom water around 5000 year BP. Nevertheless the statistical spread of ventilation within canyons across the world would itself be informative for global carbon dynamics given their ubiquity across the globe. Trouble is of course, from discussions here at Research Gate, there appears to not enough data or examples or for that matter sufficient justification for that global research question; other than what I indicated for blue carbon sequestration. furthermore, the moment my hypothesis does not have enough supporting evidence or momentum as a general consideration across the blue carbon community.

My two articles on the subject of climate effects and challenges o blue carbon implicit and explicit  assumptions will be published soon in the next month. One in a Book Chapter with Wiley Blackwell (aquaculture ecosystems) and the other in a less accessible proceeding (ICOMSA 2014; Borneo Science). The latter as part of my invitation to give a keynote address there (felt real chuffed about that haha). I have given the seminar to IMAS here in Tasmania and with a positive reception, as interesting and informative, from people who are in some way concerned with the carbon sequestration. So there is hope, should I attempt to publish now in Plos One.

One other thing TOM, is Peter Williams still there?. If so send him my regards. I was his MSc Student at Southampton years ago but I think l made some sort of impression.   

Hi John,

Yes Peter is still here (although must be in his late 70s) - although has 'supposedly' retired from science. His e-mail is [email protected]. I'm sure he'd be very pleased to hear from you.

Good luck with the Canyons work.

Tom