Palaeoclimatic interpretation of stable isotope data from Holocene speleothems of the Waitomo district, North Island, New Zealand, 1999, Williams P. W. , Marshall A. , Ford D. C. , Jenkinson A. V. ,

One straw stalactite and three stalagmites from the Waitomo district of North Island, New Zealand, were examined for stable isotopes of oxygen and carbon with a view to interpreting their palaeoclimate signal. Dating was by uranium series and AMS 14C for the stalagmites and by gamma-ray spectrometry for the straw. Records were thus established for about 100 years for the straw and 3.9, 10.1 and 10.2 ka for the stalagmites. The range of variability in d18Oc and d13Cc this century is about two-thirds of that experienced over the entire Holocene, and is most simply explained in terms of the oceanic source area of rain. Stable isotope variations in three stalagmites show some general similarities, but have significant differences in detail, which underlines the necessity to base palaeoclimatic interpretations on more than one speleothem record. The d18Oc of each stalagmite varies positively with temperature, indicating the dominance of the ocean source of evaporation in determining the isotopic composition of precipitation and hence speleothem calcite in the Holocene. This conclusion is contrary to that of other authors working in New Zealand, who identified a negative relationship between d18Oc and temperature, while examining time periods extending across the Last Glacial Maximum. It is concluded here that, whereas the ice volume effect dominates the large climatic shifts of glacial-interglacial amplitude, the oceanic source effect becomes more important during the period of relatively stable sea level during the Holocene. Results also indicate a late-Holocene altitudinal effect of 0.2{per thousand} d18Oc per 100 m and an associated temperature relationship of about 0.26{per thousand} per{degrees}C. The average of two records identifies the postglacial climatic optimum to lie in the interval from prior to 10 ka BP to 7.5 ka BP, when d18Oc values were up to 0.6{per thousand} less negative than present, implying an average annual mean temperature that was up to 2.3{degrees}C warmer. The average of three speleothem records for the last 3900 years reveals the coldest period of the Holocene to have occurred about 3 to 2 ka BP, when d18Oc values were typically 0.4{per thousand} more negative than present and average temperatures may have been 1.5{degrees}C cooler. Mean annual temperature variability of about 2{degrees}C was sometimes experienced in little more than 100 years

Constraints on Black Sea outflow to the Sea of Marmara during the last glacial-interglacial transition, 2002, Major Candace, Ryan William, Lericolais Gilles, Hajdas Irka,

New cores from the upper continental slope off Romania in the western Black Sea provide a continuous, high-resolution record of sedimentation rates, clay mineralogy, calcium carbonate content, and stable isotopes of oxygen and carbon over the last 20[punctuation space]000 yr in the western Black Sea. These records all indicate major changes occurring at 15[punctuation space]000, 12[punctuation space]800, 8400, and 7100 yr before present. These results are interpreted to reflect an evolving balance between water supplied by melting glacial ice and other river runoff and water removed by evaporation and outflow. The marked retreat of the Fennoscandian and Alpine ice between 15[punctuation space]000 and 14[punctuation space]000 yr is recorded by an increase in clays indicative of northern provenance in Black Sea sediments. A short return toward glacial values in all the measured series occurs during the Younger Dryas cold period. The timing of the first marine inflow to the Black Sea is dependent on the sill depths of the Bosporus and Dardanelles channels. The depth of the latter is known to be -805 m, which is consistent with first evidence of marine inundation in the Sea of Marmara around 12[punctuation space]000 yr. The bedrock gorge of the Bosporus reaches depths in excess of -100 m (relative to present sea level), though it is now filled with sediments to depths as shallow as -32 m. Two scenarios are developed for the connection of the Black Sea with the Sea of Marmara. One is based on a deep Bosporus sill depth (effectively equivalent to the Dardanelles), and the other is based on a shallow Bosporus sill (less than -35 m). In the deep sill scenario the Black Sea's surface rises in tandem with the Sea of Marmara once the latter connected with the Aegean Sea, and Black Sea outflow remains continuous with inflowing marine water gradually displacing the freshwater in the deep basin. The increase in the [delta]18O of mollusk shells at 12[punctuation space]800 yr and the simultaneous appearance of inorganic calcite with low [delta]18O is compatible with such an early marine water influx causing periodic weak stratification of the water column. In the shallow sill scenario the Black Sea level is decoupled from world sea level and experiences rise and fall depending on the regional water budget until water from the rising Sea of Marmara breaches the shallow sill. In this case the oxygen isotope trend and the inorganic calcite precipitation is caused by increased evaporation in the basin, and the other changes in sediment properties reflect climate-driven river runoff variations within the Black Sea watershed. The presence of saline ponds on the Black Sea shelf circa 9600 yr support such evaporative draw-down, but a sensitive geochemical indicator of marine water, one that is not subject to temperature, salinity, or biological fractionation, is required to resolve whether the sill was deep or shallow

Isotopic composition of atmospheric precipitation and karstic springs of the north-west slope of the Crimean Mountains, 2011, Dublyansky Y. V. , Klimchouk À. B. , Amelichev G. N. , Tokarev S. V. , Spötl C.

Atmospheric precipitation was sampled for isotopic analyses according to GNIP protocol at two stations in Crimea,  Ukraine: Simferopol (24 months) and Chatyrdag (15 months). In addition, several karstic springs and one well tapping deep karstic  aquifer were sampled. The δD vs. δ 18 O relationship is only slightly differs from global Meteoric Water Line. Variable degrees of  correlation with the air temperature and the precipitation amount suggest that the isotopic composition of precipitation is affected  by several processes (e.g., air temperature and supply of moisture from different sources). Interestingly, drastically different make-ups of precipitation were observed simultaneously at two stations located only 23 km apart.  Waters in seven karstic springs discharging at Dolgorukovsky massif (2), Chatirdag (1), Baidarsky basin (3), and Mangup-kale  (1) have isotopic compositions that follow local meteoric water line but are lighter than weighted annual mean values for their  respective catchment areas. Isotopic composition of the underground stream in Krasnaya (Red) cave is nearly constant and thus,  decoupled from changes in both the isotopic composition of atmospheric precipitation in the recharge area and the flow regime  (flood or base flow). This suggests a strong buffering and homogenizing role of the soil cover and the epikarst zone, as well as  the predominant role of winter recharge on these karst massifs. Still lighter isotopic composition of deep karstic water tapped by  a borehole is tentatively explained by old, pre-Holocene age of this water.

Isotopic composition of atmospheric precipitation and karstic springs of the north-west slope of the Crimean Mountains, 2012, Dublyansky Y. V. , Klimchouk À. B. , Amelichev G. N. , Tokarev S. V. , Spötl C

 

Isotopic composition of atmospheric precipitation and karstic springs of the north-west slope of the Crimean Mountains, 2012, Dublyansky Y. V. , Klimchouk À. B. , Amelichev G. N. , Tokarev S. V. , Spotl, C.

Atmospheric precipitation was sampled for isotopic analyses according to GNIP protocol at two stations in Crimea, Ukraine: Simferopol (24 months) and Chatyrdag (15 months). In addition, several karstic springs and one well tapping deep karstic aquifer were sampled. The δD vs. δ18O relationship is only slightly differs from global Meteoric Water Line. Variable degrees of correlation with the air temperature and the precipitation amount suggest that the isotopic composition of precipitation is affected by several processes (e.g., air temperature and supply of moisture from different sources). Interestingly, drastically different makeups of precipitation were observed simultaneously at two stations located only 23 km apart. Waters in seven karstic springs discharging at Dolgorukovsky massif (2), Chatirdag (1), Baidarsky basin (3), and Mangup-kale (1) have isotopic compositions that follow local meteoric water line but are lighter than weighted annual mean values for their respective catchment areas. Isotopic composition of the underground stream in Krasnaya (Red) cave is nearly constant and thus, decoupled from changes in both the isotopic composition of atmospheric precipitation in the recharge area and the flow regime (flood or base flow). This suggests a strong buffering and homogenizing role of the soil cover and the epikarst zone, as well as the predominant role of winter recharge on these karst massifs. Still lighter isotopic composition of deep karstic water tapped by a borehole is tentatively explained by old, pre-Holocene age of this water