Dear Professor Krouse,

thank you very much for your answer!
The reason for I am looking vertical d18O profile in lake water during
summer season is that we are investigating the isotopic composition of
lake water (surface) of Balaton and that of carbonate shell of Unio
Pictorum living in the same lake. Now we have the d18O time series of
surface water of Lake Balaton at Balatonszeplak 2 km offshore for the
years 2002-2004 (for three years), and d18O (and d13C) time series of an
Unio Pictorum (the shell has been microsampled along its growth
direction) who lived in the sediment of Lake Balaton at Balatonszéplak
(same settlement) 200 meters offshore. We also have the temperature (T)
time series for the water (surface). Using the T and d18O data of water
we calculated the theoritical d18O value of bioaragonite. Comparing this
theoretical d18O(aragonite) values with the neasured ones for the same
period of time we have found  significant offset for the years of 2002
and 2003, but there is no any offset for the year 2004. For the years of
2002-2003 the measured d18O is lower by 1-2 permil.
 One of our idea for this offset is vertical water stratification in
d18O, the other is that there was a significant tenperature difference
between the surface water at 2000 meters offshore and the place where
the Unio Pictorum lived: muddy layer at 200 meters offshore.
I have to notice that during the years of 2002 and 2003 the lake water
level was extremely low (dry years in this region), while the year 2004
was a normal year, the lake water was replenished.

So this is the reason we are looking for vertical d18O profile.

If you have any comment on the above observation, I would be glad to
read it.

Best regards
Istvan

Roy Krouse wrote:

>  Dear Istvan,
>  The vertical delta 18O profile of lakes can be influenced  by many
>phenomena which relate to  sources, seasonally dependent processes (
>evaporation, ice cover formation, turnover), and extent of mixing. There may
>be subsurface inputs at different levels. Surface stream inputs may slip
>under or over the surface of lake waters dependent upon relative densities
>if there is non turbulent flow. Water flow is lamellar. In the absence of
>turbulence, two waters can flow adjacent to each other vertically and
>horizontally over long distances with very slow lateral mixing. Some lakes
>have bee  stratified for very long periods of time with perhaps more saline
>bottom waters and fresher overlying waters (especially if there is ice
>cover).  Some lakes are stratified for part of the year and then undergo
>turnover. My colleagues and I have published on some of the above phenomena.
>Is your question a general one or is it related to a specific process? ( You
>mentioned surface evaporation).
>  Roy Krouse
>
>  ----- Original Message -----
>  From: "Forizs Istvan" <[log in to unmask]>
>  To: <[log in to unmask]>
>  Sent: Wednesday, April 27, 2005 12:21 AM
>  Subject: lake d18O profile
>
>
>  > Dear Listmembers,
>  >
>  > could any of you tell me a publication about the vertical d18O profile
>  > of lake water (if there is any)?
>  > I think that during strong evaporation the uppermost warm water layer is
>  > enriched in 18O, but I do not know any published data.
>  >
>  > Best regards
>  > Istvan Forizs
>  >
>  >
>  > --
>
> > -------------------------------------------------------------------------
>  > Dr. FÓRIZS István ......... Istvan FORIZS Ph.D.
>  > Magyar Tudományos Akadémia, Geokémiai Kutatóintézet
>  > Institute for Geochemical Research, Hungarian Academy of Sciences
>  > Cím/Address: H-1112 Budapest, Budaörsi út 45.   Hungary
>  > Tel./Phone: (36-1)-309-2600/ mellék/extension 1151
>  > Fax: (36-1)-319-3137
>  > Http://www.geokemia.hu/people/forizs_hu.html
>
> > -------------------------------------------------------------------------
>  >
>
>