<p>Madagascar, an island located ~300km off the eastern coast of Africa, is a natural laboratory to study paleoclimate and paleoenvironment. It holds a key position in the Indian Ocean and in Africa, as information from it has particularly helped fill gaps in paleoclimate reconstruction in the Southern Hemisphere, where such information is still scarce. Madagascar is seasonally visited by the Intertropical Convergence Zone (ITCZ) and experiences monsoon during austral summers. Furthermore, it hosts caves where speleothems can be found. Speleothems preserve a range of continuous geochemical records, mainly stable isotopes, that allow scientists to predict changes happening in the past.&#160; In Madagascar, speleothem studies have revealed distinct early, mid, and late Holocene climatic regimes that were linked to the latitudinal migration of the ITCZ, and the monsoonal responses associated with the migration. Other speleothem studies revealed evidence of the African Humid Period, rapid climate changes, and most importantly the shift in &#948;<sup>13</sup>C<sub>c</sub> starting ca. AD 800, that was attributed to anthropogenic activities. Although information from these speleothems is unquestionably significant, there are still gaps in isotopic proxies interpretation, mainly in linking modern environments where these speleothems grew and the signals they preserve. Such modern information is however fundamental to calibrate paleo-based climate and environmental reconstructions in Madagascar, which could be a key to refine their past interpretation. In this study, we performed an in-cave spatial test to understand kinetic isotope effect in Anjohibe Cave and to define oxygen isotopic fractionation between speleothem carbonate and its parent water and carbon isotopic fractionation between speleothem carbonate and the corresponding dissolved inorganic carbon (DIC). Results have been compared with modern calibration studies on speleothems from other locations worldwide, and we found that our data fit within the empirical relationship for cave-specific CaCO<sub>3</sub>-H<sub>2</sub>O isotope fractionation, grouping a range of monitored caves worldwide, 1000 ln &#945;&#160;= 16.1 (10<sup>3</sup>T<sup>-1</sup>(&#176;K))&#8211;24.6 of Tremaine et al. (2011). Other physico-chemical parameters in Anjohibe Cave have also been measured, and they will be used to discuss potential linkages with the spatial variability in the&#160; modern speleothem stable isotopic values and their corresponding parent water and DIC.</p><p><em>Tremaine, D.M., Froelich, P.N., Wang, Y., 2011. Speleothem calcite farmed in situ: Modern calibration of &#948;<sup>18</sup>O and &#948;<sup>13</sup>C paleoclimate proxies in a continuously-monitored natural cave system. Geochim Cosmochim Acta 75, 4929-4950.</em></p>
<p>Caves are an excellent natural laboratory for understanding the transfer processes of the region&#8217;s environmental signals to speleothems. At least eight speleothems have produced high resolution paleoclimate and paleoenvironment records from Anjohibe Cave, NW Madagascar. However, due to the remote and difficult access to many caves in Madagascar, no studies have yet been done to understand the transfer of climate and environmental changes of the region to the cave. This is the first monitoring study to understand the linkage between regional climatology and various responses in Anjohibe Cave. We monitored (1) the drip water pH, TDS, EC, temperature, &#948;<sup>13</sup>C<sub>DIC</sub>, &#948;<sup>18</sup>O<sub>w</sub>, &#948;<sup>2</sup>H<sub>w</sub>, and elemental (Ca, Mg, Sr) composition, and (2) the cave atmosphere <em>p</em>CO<sub>2</sub>, relative humidity and temperature. Results show that air-to-air transfer is fast, and the internal parameters closely vary with the regional climatology. In contrast, rainfall to drip signal transfer is not immediate, and it can take few months to one season for the signals to be detected in the drip water due to the &#8220;epikarst storage effect&#8221;. The deposition of CaCO<sub>3</sub> is inferred to occur late in the dry austral winter season, during which prior carbonate precipitation was also detected. Since the growth of speleothems is influenced by numerous cave-specific factors, this study, although preliminary, indicates that Anjohibe Cave drip waters are capable of registering changes in its surrounding environment. A longer monitoring study is expected in the future to constrain the timing and the mode of transfer.</p>
