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A concerted effort has begun to gather and preserve archives of marine samples and descriptive data, giving scientists ready access to insights on ancient environments.

A concerted effort has begun to gather and preserve archives of marine samples and descriptive data, giving scientists ready access to insights on ancient environments.

Evidence from geologic archives suggests that there were large changes in the tropical hydrologic cycle associated with the two prominent northern hemisphere deglacial cooling events, Heinrich Stadial 1 (HS1; similar to 19 to 15 kyr BP; kyr BP = 1000 yr before present) and the Younger Dryas (similar to 12.9 to 11.7 kyr BP). These hydrologic shifts have been alternatively attributed to high and low latitude origin. Here, we present a new record of hydrologic variability based on planktic foraminifera-derived delta O-18 of seawater (delta O-18(sw)) estimates from a sediment core from the tropical Eastern Indian Ocean, and using 12 additional delta O-18(sw) records, construct a single record of the dominant mode of tropical Eastern Equatorial Pacific and Indo-Pacific Warm Pool (IPWP) hydrologic variability. We show that deglacial hydrologic shifts parallel variations in the reconstructed interhemispheric temperature gradient, suggesting a strong response to variations in the Atlantic Meridional Overturning Circulation and the attendant heat redistribution. A transient model simulation of the last deglaciation suggests that hydrologic changes, including a southward shift in the Intertropical Convergence Zone (ITCZ) which likely occurred during these northern hemisphere cold events, coupled with oceanic advection and mixing, resulted in increased salinity in the Indonesian region of the IPWP and the eastern tropical Pacific, which is recorded by the delta O-18(sw) proxy. Based on our observations and modeling results we suggest the interhemispheric temperature gradient directly controls the tropical hydrologic cycle on these time scales, which in turn mediates poleward atmospheric heat transport.

Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and delta O-18 for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1-2 degrees C larger temperature decrease between 17 degrees and 20 degrees S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.

Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and delta O-18 for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1-2 degrees C larger temperature decrease between 17 degrees and 20 degrees S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.

Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and delta O-18 for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1-2 degrees C larger temperature decrease between 17 degrees and 20 degrees S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.

Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and delta O-18 for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1-2 degrees C larger temperature decrease between 17 degrees and 20 degrees S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.

In the context of increasing anthropogenic CO2 emissions, determining the rate of oceanic CO2 uptake is of high interest. Centennial-scale changes in delta C-13 of the surface water dissolved inorganic carbon (DIC) reservoir have been shown to be influenced by the carbon isotopic composition of atmospheric CO2. However, the availability of direct oceanic delta C-13 measurements is limited and methods for reconstructing past delta C-13 variability of the oceanic DIC are needed. Geochemical reconstructions of DIC variability can help in understanding how the ocean has reacted to historical changes in the carbon cycle. This study explores the potential of using temporal variations in delta C-13 measured in five Fijian Porites corals for reconstructing oceanic delta C-13 variability. A centennial-scale decreasing delta C-13 trend is observed in these Fiji corals. Other studies have linked similar decreasing delta C-13 trends to anthropogenic changes in the atmospheric carbon reservoir (the "C-13 Suess effect"). We conclude that solar irradiance is the factor influencing the delta C-13 cycle on a seasonal scale, however it is not responsible for the centennial-scale decreasing delta C-13 trend. In addition, variations in skeletal extension rate are not found to account for centennial-scale delta C-13 variability in these corals. Rather, we found that water depth at which a Fijian Porites colony calcifies influences both delta C-13 and extension rate mean values. The water depth-delta C-13 relationship induces a dampening effect on the centennial-scale decreasing delta C-13 trend. We removed this "water depth effect" from the 813C composite, resulting in a truer representation of delta C-13 variability of the Fiji surface water DIC (delta C-13(Fiji-DIC)). The centennial-scale trend in this Fiji coral composite delta C-13(Fiji-DIC) time-series shares similarities with atmospheric delta C-13(CO2), implicating the C-13 Suess effect as the source of the this coral delta C-13

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013): 3730–3750, doi:10.1002/ggge.20230., The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1., E.C.H. (MARUM Fellowship) and T.F. were supported by the DFG-Research Center/Excellence Cluster ‘‘The Ocean in the Earth System,’’ University of Bremen. HVM was supported by an AINSE Research Fellowship., 2014-03-23

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013): 3730–3750, doi:10.1002/ggge.20230., The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1., E.C.H. (MARUM Fellowship) and T.F. were supported by the DFG-Research Center/Excellence Cluster ‘‘The Ocean in the Earth System,’’ University of Bremen. HVM was supported by an AINSE Research Fellowship., 2014-03-23

In the context of increasing anthropogenic CO2 emissions, determining the rate of oceanic CO2 uptake is of high interest. Centennial-scale changes in delta C-13 of the surface water dissolved inorganic carbon (DIC) reservoir have been shown to be influenced by the carbon isotopic composition of atmospheric CO2. However, the availability of direct oceanic delta C-13 measurements is limited and methods for reconstructing past delta C-13 variability of the oceanic DIC are needed. Geochemical reconstructions of DIC variability can help in understanding how the ocean has reacted to historical changes in the carbon cycle. This study explores the potential of using temporal variations in delta C-13 measured in five Fijian Porites corals for reconstructing oceanic delta C-13 variability. A centennial-scale decreasing delta C-13 trend is observed in these Fiji corals. Other studies have linked similar decreasing delta C-13 trends to anthropogenic changes in the atmospheric carbon reservoir (the "C-13 Suess effect"). We conclude that solar irradiance is the factor influencing the delta C-13 cycle on a seasonal scale, however it is not responsible for the centennial-scale decreasing delta C-13 trend. In addition, variations in skeletal extension rate are not found to account for centennial-scale delta C-13 variability in these corals. Rather, we found that water depth at which a Fijian Porites colony calcifies influences both delta C-13 and extension rate mean values. The water depth-delta C-13 relationship induces a dampening effect on the centennial-scale decreasing delta C-13 trend. We removed this "water depth effect" from the 813C composite, resulting in a truer representation of delta C-13 variability of the Fiji surface water DIC (delta C-13(Fiji-DIC)). The centennial-scale trend in this Fiji coral composite delta C-13(Fiji-DIC) time-series shares similarities with atmospheric delta C-13(CO2), implicating the C-13 Suess effect as the source of the this coral delta C-13

The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twentyone laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp- 1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

In the context of increasing anthropogenic CO2 emissions, determining the rate of oceanic CO2 uptake is of high interest. Centennial-scale changes in delta C-13 of the surface water dissolved inorganic carbon (DIC) reservoir have been shown to be influenced by the carbon isotopic composition of atmospheric CO2. However, the availability of direct oceanic delta C-13 measurements is limited and methods for reconstructing past delta C-13 variability of the oceanic DIC are needed. Geochemical reconstructions of DIC variability can help in understanding how the ocean has reacted to historical changes in the carbon cycle. This study explores the potential of using temporal variations in delta C-13 measured in five Fijian Porites corals for reconstructing oceanic delta C-13 variability. A centennial-scale decreasing delta C-13 trend is observed in these Fiji corals. Other studies have linked similar decreasing delta C-13 trends to anthropogenic changes in the atmospheric carbon reservoir (the "C-13 Suess effect"). We conclude that solar irradiance is the factor influencing the delta C-13 cycle on a seasonal scale, however it is not responsible for the centennial-scale decreasing delta C-13 trend. In addition, variations in skeletal extension rate are not found to account for centennial-scale delta C-13 variability in these corals. Rather, we found that water depth at which a Fijian Porites colony calcifies influences both delta C-13 and extension rate mean values. The water depth-delta C-13 relationship induces a dampening effect on the centennial-scale decreasing delta C-13 trend. We removed this "water depth effect" from the 813C composite, resulting in a truer representation of delta C-13 variability of the Fiji surface water DIC (delta C-13(Fiji-DIC)). The centennial-scale trend in this Fiji coral composite delta C-13(Fiji-DIC) time-series shares similarities with atmospheric delta C-13(CO2), implicating the C-13 Suess effect as the source of the this coral delta C-13

The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twentyone laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp- 1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twentyone laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp- 1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): D19108, doi:10.1029/2012JD018060., Existing paleoclimate data suggest a complex evolution of hydroclimate within the Indo-Pacific Warm Pool (IPWP) during the Holocene epoch. Here we introduce a new leaf wax isotope record from Sulawesi, Indonesia and compare proxy water isotope data with ocean-atmosphere general circulation model (OAGCM) simulations to identify mechanisms influencing Holocene IPWP hydroclimate. Modeling simulations suggest that orbital forcing causes heterogenous changes in precipitation across the IPWP on a seasonal basis that may account for the differences in time-evolution of the proxy data at respective sites. Both the proxies and simulations suggest that precipitation variability during the September–November (SON) season is important for hydroclimate in Borneo. The preëminence of the SON season suggests that a seasonally lagged relationship between the Indian, J. Tierney acknowledges the NOAA Climate and Global Change Postdoctoral Fellowship for support., 2013-04-04

Existing paleoclimate data suggest a complex evolution of hydroclimate within the Indo-Pacific Warm Pool (IPWP) during the Holocene epoch. Here we introduce a new leaf wax isotope record from Sulawesi, Indonesia and compare proxy water isotope data with ocean-atmosphere general circulation model (OAGCM) simulations to identify mechanisms influencing Holocene IPWP hydroclimate. Modeling simulations suggest that orbital forcing causes heterogenous changes in precipitation across the IPWP on a seasonal basis that may account for the differences in time-evolution of the proxy data at respective sites. Both the proxies and simulations suggest that precipitation variability during the September–November (SON) season is important for hydroclimate in Borneo. The preëminence of the SON season suggests that a seasonally lagged relationship between the Indian

Core top samples from Indonesian and northeast Atlantic depth transects were used to calibrate Mg/Ca and delta O-18 in tests of the calcitic benthic foraminifer Hyalinea balthica to bottom water temperature between 4 degrees C and 13 degrees C. This shallow infaunal species is primarily abundant in neritic to upper bathyal sediments (< 600 m). Both linear and exponential calibrations suggest a temperature sensitivity of similar to 12% per degrees C that is similar to 4 times higher than observed in other species of deep-sea benthic foraminifera. Culture experiments support the core top calibration. We find no discernible effect of salinity and saturation on Mg/Ca. Comparison between the measured benthic foraminiferal delta O-18 and predicted equilibrium values suggests that on average H. balthica delta O-18 is 0.64 parts per thousand similar to 0.13 parts per thousand lower than predicted from the equilibrium composition. To test the reliability of using paired H. balthica Mg/Ca and delta O-18 measurements for reconstructing seawater delta O-18(sw) and salinity, we apply this calibration to another depth transect from Cape Ghir off NW Africa, which was not included in the calibration. Based on error analysis of the calibration data and this validation test, we show that the uncertainty of reconstructing bottom water temperature and salinity from paired Mg/Ca and delta O-18 measurements of H. balthica is better than +/- 0.7 degrees C and +/- 0.69 practical salinity scale, respectively. The small uncertainties allow for the reconstruction of seawater density to better than 0.3 sigma(theta) units, which is precise enough for the identification of specific water masses and reconstruction of changes in their properties. We propose that the relatively high Mg content and temperature sensitivity of H. balthica might be due to minor, biologically mediated contribution of high-Mg calcite to the primarily low Mg calcite test, which is influenced by the ambient temperature. Th

Core top samples from Indonesian and northeast Atlantic depth transects were used to calibrate Mg/Ca and delta O-18 in tests of the calcitic benthic foraminifer Hyalinea balthica to bottom water temperature between 4 degrees C and 13 degrees C. This shallow infaunal species is primarily abundant in neritic to upper bathyal sediments (< 600 m). Both linear and exponential calibrations suggest a temperature sensitivity of similar to 12% per degrees C that is similar to 4 times higher than observed in other species of deep-sea benthic foraminifera. Culture experiments support the core top calibration. We find no discernible effect of salinity and saturation on Mg/Ca. Comparison between the measured benthic foraminiferal delta O-18 and predicted equilibrium values suggests that on average H. balthica delta O-18 is 0.64 parts per thousand similar to 0.13 parts per thousand lower than predicted from the equilibrium composition. To test the reliability of using paired H. balthica Mg/Ca and delta O-18 measurements for reconstructing seawater delta O-18(sw) and salinity, we apply this calibration to another depth transect from Cape Ghir off NW Africa, which was not included in the calibration. Based on error analysis of the calibration data and this validation test, we show that the uncertainty of reconstructing bottom water temperature and salinity from paired Mg/Ca and delta O-18 measurements of H. balthica is better than +/- 0.7 degrees C and +/- 0.69 practical salinity scale, respectively. The small uncertainties allow for the reconstruction of seawater density to better than 0.3 sigma(theta) units, which is precise enough for the identification of specific water masses and reconstruction of changes in their properties. We propose that the relatively high Mg content and temperature sensitivity of H. balthica might be due to minor, biologically mediated contribution of high-Mg calcite to the primarily low Mg calcite test, which is influenced by the ambient temperature. Th

Core top samples from Indonesian and northeast Atlantic depth transects were used to calibrate Mg/Ca and delta O-18 in tests of the calcitic benthic foraminifer Hyalinea balthica to bottom water temperature between 4 degrees C and 13 degrees C. This shallow infaunal species is primarily abundant in neritic to upper bathyal sediments (< 600 m). Both linear and exponential calibrations suggest a temperature sensitivity of similar to 12% per degrees C that is similar to 4 times higher than observed in other species of deep-sea benthic foraminifera. Culture experiments support the core top calibration. We find no discernible effect of salinity and saturation on Mg/Ca. Comparison between the measured benthic foraminiferal delta O-18 and predicted equilibrium values suggests that on average H. balthica delta O-18 is 0.64 parts per thousand similar to 0.13 parts per thousand lower than predicted from the equilibrium composition. To test the reliability of using paired H. balthica Mg/Ca and delta O-18 measurements for reconstructing seawater delta O-18(sw) and salinity, we apply this calibration to another depth transect from Cape Ghir off NW Africa, which was not included in the calibration. Based on error analysis of the calibration data and this validation test, we show that the uncertainty of reconstructing bottom water temperature and salinity from paired Mg/Ca and delta O-18 measurements of H. balthica is better than +/- 0.7 degrees C and +/- 0.69 practical salinity scale, respectively. The small uncertainties allow for the reconstruction of seawater density to better than 0.3 sigma(theta) units, which is precise enough for the identification of specific water masses and reconstruction of changes in their properties. We propose that the relatively high Mg content and temperature sensitivity of H. balthica might be due to minor, biologically mediated contribution of high-Mg calcite to the primarily low Mg calcite test, which is influenced by the ambient temperature. Th

To evaluate and extend the record of decadal climate variability, we present a synthesis of 23 coral oxygen isotope records from the tropical Indo-Pacific that extends back to A.D. 1850. Principal components analysis (PCA) on detrended records reveals a leading pattern of variance with significant interannual (3-5 year) and decadal (9-14 year) variability. The temporal evolution and spatial pattern of this variability closely resembles the El Nino/Southern Oscillation (ENSO) pattern across both time scales, suggesting that this decadal tropical variability is fundamentally related to ENSO. The 19th century experienced stronger decadal tropical climate variability, compared to the 20th. Decadal variability in the tropical oceans thus remains underestimated by analysis of direct observations.