Cave atmosphere controls on stalagmite growth rate and palaeoclimate records - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 288

ions may also attenuate the growth of fast growing
crystal faces. For example, free orthophosphate
ions may inhibit the growth of certain types of
calcite (Borsato et al. 2007; Dove & Hochella
1993). Because these ions and colloids are often
preferentially released during certain seasons, crys-
tallographic factors independent of cave air P CO 2
may also influence calcite growth timing through
the year.

References
A TKINSON , T. C. 1977. Carbon dioxide in the atmosphere
of the unsaturated zone: an important control of
groundwater hardness in limestones. Journal of
Hydrology, 35, 111-123.
B AKER ,A.&G ENTY , A. 1998. Environmental pressures
on conserving cave speleothems: effects of changing
surface land use and increased cave tourism. Journal
of Environmental Management, 53(2), 165-175.
B AKER , A., G ENTY , D., D REYBRODT , W., G RAPES ,J.&
M OCKLER , N. J. 1998. Testing theoretically predicted
stalagmite growth rates with recent annually lami-
nated samples: implications for past stalagmite depo-
sition. Geochimica et Cosmochimica Acta, 62,
393-404.
B ALDINI , J. U. L., B ALDINI , L. M., M C D ERMOTT ,F.&
C LIPSON , N. 2006. Carbon dioxide sources, sinks,
and spatial variability in shallow temperate zone
caves: evidence from Ballynamintra Cave, Ireland.
Journal of Cave and Karst Studies, 68(1), 4-11.
B ALDINI , J. U. L., M C D ERMOTT , F., B AKER , A.,
B ALDINI , L. M., M ATTEY ,D.P.&R AILSBACK ,
L. B. 2005. Biomass effects on stalagmite growth
and isotope ratios: A 20th century analogue from
Wiltshire, England. Earth Planetary Science Letters,
240, 486-494.
B ALDINI , J. U. L., M C D ERMOTT ,F.&F AIRCHILD ,I.J.
2002. Structure of the 8200-year cold event revealed
by a speleothem trace element

Conclusions/future work

Monitoring studies are continuing to clarify how
cave air P CO 2 changes through time. Production from
the soil zone appears to be the most important source
of CO 2 in many temperate non-geothermal cave
sites, but this is often overprinted by ventilation
effects. Caves in locations with the highest mean
annual temperature also typically have the highest
maximum cave air P CO 2 values. There is no apparent
relationship between the maximum values at indi-
vidual cave sites and the minimum values, which
typically appear to be controlled by ventilation.
Cave air P CO 2 affects stalagmite growth rate
directly by controlling the differential between soil
and cave air P CO 2 and consequently the percolation
water's thermodynamic drive to degas. For drip sites
where the hydrochemistry is responsive to recent
weather conditions temperature-dependent soil
CO 2 production increases percolation water DIC
and consequently affects the amount of carbonate
rock dissolution. This then raises the [Ca 2þ ] of the
percolation water which increases stalagmite
growth rate during seasons where elevated cave
atmosphere P CO 2 typically discourages calcite depo-
sition. However, annual- to sub-annual scale varia-
bility in stalagmite proxy records fed by very
time-averaged ('diffuse' or 'seepage') drips may
be almost completely modulated by shifts in cave
air P CO 2 .
Further work needs to clarify the relationship
between climate and cave air P CO 2 . More time
series records are necessary from caves in different
climates to refine existing models to include soil
moisture content. Furthermore, more monitoring
studies should attempt to verify the relationship bet-
ween calcite deposition and all the calcite growth
determining variables. Because of the importance
of cave air P CO 2 variability on the emplacement of
stalagmite geochemical proxy records, measuring
cave air composition at any cave site of palaeocli-
matic interest for at least one year would greatly
assist with proxy record interpretation.

record. Science,

296(5576), 2203-2206.
B ALDINI , J. U. L., M C D ERMOTT , F., H OFFMANN , D. L.,
R ICHARDS ,D.A.&C LIPSON , N. 2008. Very high-
frequency and seasonal cave atmosphere P CO2 variabil-
ity: implications for stalagmite growth and oxygen
isotope-based paleoclimate records. Earth and Plane-
tary Science Letters, 272(1-2), 118-129.
B ANNER , J. L., G UILFOYLE , A., J AMES , E. W., S TERN ,
L. A. & M USGROVE , M. 2007. Seasonal variations
in modern speleothem calcite growth in Central
Texas, USA. Journal of Sedimentary Research,
77(7-8), 615-622.
B ERGER , J. 1988. Do heavy gases fall? European Journal
of Physics, 9, 335.
B ORSATO , A., F RISIA , S., F AIRCHILD , I. J., S OMOGYI ,A.
&S USINI , J. 2007. Trace element distribution in
annual stalagmite laminae mapped by micrometer-
resolution X-ray fluorescence: implications for
incorporation of environmentally significant species.
Geochimica et Cosmochimica Acta, 71(6), 1494-
1512.
B OURGES , F., M ANGIN ,A.& D 'H ULST , D. 2001. Le gaz
carbonique dans la dynamique de l'atmosph`re des
cavit´s karstique: l'exemple de l'Aven d'Orgnac
(Ard`che). Earth and Planetary Sciences, 333,
685-692.
B UHMANN ,D.&D REYBRODT , W. 1985a. The kinetics of
calcite dissolution and precipitation in geologically
relevant situations of karst areas. 1. Open System.
Chemical Geology, 48(1-4), 189-211.
B UHMANN ,D.&D REYBRODT , W. 1985b. The kinetics of
calcite dissolution and precipitation in geologically
relevant situations of karst areas. 2. closed system.
Chemical Geology, 53(1-2), 109-124.

Prof. DaveMattey and Dr Silvia Frisia are thanked for their
reviews and useful suggestions which helped improve the
manuscript. Prof. Ian Fairchild and Dr Lisa Baldini are also
thanked for useful discussions.