Yair Rosenthal - Academia.edu (original) (raw)
Papers by Yair Rosenthal
Earth and Planetary Science Letters, 2002
We have generated benthic foraminiferal Mg/Ca records from eastern tropical Atlantic core M16772 ... more We have generated benthic foraminiferal Mg/Ca records from eastern tropical Atlantic core M16772 (3.9 km) and eastern tropical Pacific core TR163-31P (3.2 km) to assess the potential for using benthic Mg-paleothermometry to reconstruct Quaternary bottom water temperature histories. Variations in Mg/Ca records from both the Atlantic and Pacific show a significant correlation with climatic oscillations of the last 330 kyr. Shell Mg/Ca peaks during interglacial episodes, with marine isotope stage (MIS) 5e Mg/Ca nearly matching Holocene values in both cores. Lower Mg/Ca values occur during glacial intervals. To estimate temperatures from downcore Mg/Ca, we have augmented the published Cibicidoides sp. Mg/Ca^temperature dataset [Rosenthal et al., Geochim. Cosmochim. Acta 61 (1997) 3633^3643] with new data to include the temperature range of deep waters. Applying the 10.9% change in Mg/Ca per ‡C defined by the expanded calibration to the deep Atlantic data implies glacial^interglacial shifts in deep water temperature of 2^4 ‡C over the last 300 kyr. Temperature estimates are comparable to deep Atlantic temperature changes proposed by Labeyrie et al. [Nature 327 (1987) 477^482]. There is greater uncertainty in deriving temperatures from the tropical Pacific core due to a limited Uvigerina spp. core top calibration set; however, glacialî nterglacial temperature oscillations appear to be on the order of 2^3 ‡C. In addition, core TR163-31P records clear millennial-scale Mg/Ca and N 18 O oscillations in MIS 3 corresponding to temperature fluctuations of s 0.5 ‡C. Additional calibration studies are needed to address potential secondary effects on Mg/Ca.
Earth and Planetary Science Letters, 2003
The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Nor... more The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Northern Hemisphere Glaciation (NHG). The cause and effects of these changes are still debated. We use a multiproxy approach to determine the relative timing of the closure of the Panama gateway, changes in Atlantic circulation, global cooling and ice sheet growth. Benthic foraminiferal Mg/Ca records from a Pacific and an Atlantic Site have been produced and are interpreted in terms of bottom water temperatures. These Mg-temperature records are combined with published benthic N 13 C, N 18 O and erosion records to reconstruct the flow of proto-North Atlantic Deep Water (proto-NADW) over the past 12 Ma. The results suggest that between 12.5 and 10.5 Ma, and again between about 8.5 and 6 Ma, a nutrient-depleted water mass that was colder (by 1^2 ‡C) and fresher than the intervening deep water mass filled the Atlantic basin. This proto-NADW became warmer (by V1 ‡C) and saltier between 6 and 5 Ma, coincident with the restriction of surface water flow through the Central American Seaway. The Mg-temperature records define a subsequent global cooling trend of V3.5 ‡C between 5 Ma and today. Early NHG in the late Miocene was perhaps related to the formation of the relatively cold, fresh proto-NADW. The formation of the warmer and saltier proto-NADW in the early Pliocene may have initially limited Northern Hemisphere ice growth. However, the increased moisture released at high northern latitudes associated with formation of 'warm' proto-NADW, coupled with the global temperature decrease of deep (and hence polar surface) waters, likely helped initiate the intense NHG of the Plio^Pleistocene.
Ecological Engineering, 1999
Accurate measurements of atmospheric CO 2 concentrations are performed routinely in a variety of ... more Accurate measurements of atmospheric CO 2 concentrations are performed routinely in a variety of experimental settings including open fields and forests, leaf gas-exchange chambers, phytotrons and specialized growth chambers. However, the accurate monitoring of large scale structurally and biologically complex experimental systems, operating as materially closed systems, is not widely reported. Here we report the design elements, material specifications and other details for high precision monitoring of CO 2 in Biosphere 2, a large scale ecologically diverse experimental facility located in Oracle, AZ. The results are used to illustrate how carbon balance in a temporarily isolated subsystem of the facility is used to assess carbon dynamics under different environmental conditions such as variable atmospheric CO 2 levels, temperature, light, and soil moisture. The analytical system described here should be applicable for any settings in which continuous, high accuracy measurements of CO 2 in a complex system are needed for quantitative research.
Geochemistry, Geophysics, Geosystems, 2006
Improving interlaboratory reproducibility (in both precision and accuracy) of Mg/Ca and Sr/Ca det... more Improving interlaboratory reproducibility (in both precision and accuracy) of Mg/Ca and Sr/Ca determination in marine biogenic carbonates is critical in optimizing their utility as paleothermometers. Coupled with a need for uniform sample cleaning practices, there is a need for more exacting methods and procedures across laboratories using varied instrumentation. Here we employ an intensity ratio/matrixeffect correction methodology to a suite of solution standards and biogenic carbonates (foraminifera tests and a gastropod shell) to investigate short-term and long-term Mg/Ca and Sr/Ca precision and accuracy by different instruments: a magnetic-sector inductively coupled plasma-mass spectrometer (ICP-MS) and a radially viewed inductively coupled plasma-optical emission spectrophotometer (ICP-OES). Over an extended 1.0-24.5 mM Ca concentration range, both instruments have significant Ca matrix effects for Mg/Ca and somewhat less for Sr/Ca. Over our working Ca range (1-8 mM Ca), Mg/Ca matrix effects are significant, requiring correction, and Sr/Ca matrix effects are small to negligible, occasionally requiring correction (linear or logarithmic fit) using a suite of matrix standards for both instruments. The short-term (intrarun) precision for a suite of solution standards is <0.2% (1s %RSD) for Mg/Ca and Sr/Ca for both instruments. A long-term (interrun) precision of <0.9% is demonstrated for Mg/Ca and <0.6% for Sr/Ca on both instruments. The accuracy of measured Mg/Ca and Sr/Ca values for short-and long-term standards is similar on both instruments at better than 1 ± 0.5%, on par with our long-term precision. An interinstrument comparison of the same measured suite of biogenic carbonates demonstrates that after accounting for matrix effects, data generated on either instrument are essentially interchangeable (within analytical precision) to a high degree of fidelity.
The Journal of …, 2010
Geochemical analyses of the carbonate tests calcified by foraminifera have provided much of the f... more Geochemical analyses of the carbonate tests calcified by foraminifera have provided much of the foundation for reconstructions of past ocean and climate conditions, and for chemostratigraphy. In particular, reconstructions of climate history (including temperature, ...
Analytical Chemistry, 1999
A new method was developed for rapid and precise simultaneous determination of Mg/Ca, Sr/Ca, Mn/C... more A new method was developed for rapid and precise simultaneous determination of Mg/Ca, Sr/Ca, Mn/Ca, Cd/Ca, Ba/Ca and U/Ca ratios in foraminiferal shells using sector field inductively coupled plasma mass spectrometry (ICPMS). Element/calcium ratios were determined directly from intensity ratios using external, matrixmatched standard to correct for instrumental mass discrimination. Because of large differences in the abundance of chemical constituents of the foraminiferal shell, major elemental ratios were determined in analog mode (using 24 Mg, 43 Ca, 44 Ca, 55 Mn, and 88 Sr) whereas trace elemental ratios were determined in pulse-counting mode (using 111 Cd, 138 Ba, 238 U, and the low-abundance 46 Ca isotope). Matrix-induced variations in mass discrimination over a calcium concentration range of 2.0-24.5 mM were observed only for Mg/Ca and Cd/Ca ratios. However, these effects are negligible if the samples and standard calcium concentration are within a factor of 2-3. Multiratio method reproducibility was better than previously reported for other ICPMS methods yielding precision (1σ) of Sr/Ca ) 0.45%; Mg/Ca ) 0.45%, Mn/Ca ) 0.8%, Cd/ Ca ) 1.7%, Ba/Ca ) 0.7%, and U/Ca ) 1.4% for foraminifera samples as small as 25 µg. Using this approach for a single-ratio analysis, Sr/Ca ratios were determined with precision of 0.06% (1σ) on carbonate samples as small as a single foraminifera shell (<10 µg). The new method is more sensitive, more precise, and simpler to use than previously available ICPMS techniques. It provides an efficient tool for simultaneous determination of several elemental ratios of paleoceanographic interest in a single foraminiferal sample, thereby reducing overall sample size requirement and analysis time.
Geochimica Et Cosmochimica Acta, 2002
... Climate proxies from Sr/Ca of coccolith calcite: calibrations from continuous culture of Emil... more ... Climate proxies from Sr/Ca of coccolith calcite: calibrations from continuous culture of Emiliania huxleyi. ... primary producers, the trace element chemistry of their shells may provide different information than that of foraminifera or corals commonly used in paleoceanographic ...
Geochimica Et Cosmochimica Acta, 1993
This work is an assessment of the effects of seawater salinity and temperature on the incorporati... more This work is an assessment of the effects of seawater salinity and temperature on the incorporation of fluoride into calcitic shells of planktonic foraminifera and of the subsequent modification of shell chemistry by postdepositional dissolution. A strong correlation between the fluoride content of most planktonic species and their calcification depth was observed, deeper-calcifying foraminifera have lower fluoride content and heavier '*O composition, perhaps suggesting a temperature control on the partition coefficient. However, species deviations from this general trend and the absence of correlation between fluoride and sea-surface temperature within an individual species suggest that the coprecipitation of fluoride in foraminiferal calcite is more strongly controlled by biological processes rather than by simple chemical relationships. Foraminiferal fluoride shows weak or no correlation with sea-surface salinity.
Geochimica Et Cosmochimica Acta, 1997
Earth and Planetary Science Letters, 1995
Geochemistry Geophysics Geosystems, 2003
1] We have generated a new high-resolution record of variations in planktonic foraminiferal oxyge... more 1] We have generated a new high-resolution record of variations in planktonic foraminiferal oxygen isotopes (d 18 O) and Mg/Ca from a sediment core (IMAGES 97-2141) in the Sulu Sea located in the Philippine archipelago of western tropical Pacific. This record reveals distinct, suborbital-scale d 18 O changes, most notably during Marine Isotope Stage 3 (MIS3) ($30,000 to 60,000 years B.P.). The amplitudes of these d 18 O fluctuations (0.4 to 0.7%) exceed that which can be attributed to sea level changes and must be due to changes in sea surface conditions. In the same interval, variations in planktonic foraminifera Mg/Ca suggest that suborbital surface ocean temperature variations of 1 to 1.5°C in the Sulu Sea were not in phase with d 18 O. Combined, this evidence indicates that the MIS3 millennial d 18 O events in the Sulu Sea were primarily the result of changes in surface water salinity, which today is directly related to the East Asian Monsoon (EAM) and its influence on the balance between surface water contributions from the South China Sea and Western Pacific Warm Pool (WPWP). Within dating uncertainties the MIS3 Sulu Sea d 18 O suborbital variability indicates that times of fresher surface conditions in the Sulu Sea coincide with similar conditions in the WPWP and also with intensifications of the summer EAM as recorded in the U-Th dated Chinese (Hulu Cave) speleothem d 18 O record and thus by inference with interstadials in the Greenland Ice core records. Combined, these results indicate that pronounced suborbital variability in the summer EAM and Intertropical Convergence Zone (ITCZ) during MIS3 was tightly coupled with climate conditions in the northern high latitudes.
Geochemistry Geophysics Geosystems, 2003
1] A detailed record of planktic d 18 O from a sediment core in the Sulu Sea, located between the... more 1] A detailed record of planktic d 18 O from a sediment core in the Sulu Sea, located between the South China Sea and the western Pacific warm pool, reveals that for the past 400 kyr (1 kyr = 1000 years), d 18 O variability on orbital timescales is similar to that caused by changes in ice volume alone. This result indicates that in the Sulu Sea, temperature-driven changes in planktic d 18 O on orbital times scales were generally compensated for by the effects of sea level and changes in seasonal monsoon intensity on the local freshwater budget, as well as by other changes in the tropical hydrologic cycle and their attendant effects on surface water d 18 O. Increased freshening of the western tropical Pacific warm pool is reminiscent of La Niña conditions. However, we argue that the mean tropical climate state was not more La Niña-like than today on broader spatial scales. Suborbital variability occurred in the Sulu Sea throughout the past 400 kyr, suggesting little sensitivity to ice volume or to glacial-interglacial changes in tropical hydrology. Variations on 4-10 kyr timescales appear to be linked to those in the North Atlantic region, suggesting a common forcing of that variability. We suggest that Sulu Sea salinity variations were a response to suborbital climate variability in the North Atlantic region, transmitted via changes in the intensity of the East Asian summer monsoon. We suggest that a North Atlantic origin of that tropical suborbital variability can be reconciled with weak glacial amplification in the tropics if the tropical response is nonlinear.
1] Paired benthic foraminiferal trace metal and stable isotope records have been constructed from... more 1] Paired benthic foraminiferal trace metal and stable isotope records have been constructed from equatorial Pacific Ocean Drilling Program Site 1218. The records include the two largest abrupt (<1 Myr) increases in the Cenozoic benthic oxygen isotope record: Oi-1 in the earliest Oligocene ($34 Ma) and Mi-1 in the earliest Miocene ($23 Ma). The paired Mg/Ca and oxygen isotope records are used to calculate seawater d 18 O (dw). Calculated dw suggests that a large Antarctic ice sheet formed during Oi-1 and subsequently fluctuated throughout the Oligocene on both short (<0.5 Myr) and long (2-3 Myr) timescales, between about 50 and 100% of its maximum earliest Oligocene size. The magnitudes of these fluctuations are consistent with estimates of sea level derived from sequence stratigraphy. The transient expansion of the Antarctic ice sheet at Mi-1 is marked in the benthic d 18 O record by two positive excursions between 23.7 and 22.9 Ma, each with a duration of 200-300 kyr. Bottom water temperatures decreased by 2°Coverthe150kyrimmediatelypriortobothrapidd18Oexcursions.However,theonsetofeachofthesephasesoficegrowthissynchronous,withintheresolutionoftherecords,withtheonsetofa2°Cwarmingover2°C over the 150 kyr immediately prior to both rapid d 18 O excursions. However, the onset of each of these phases of ice growth is synchronous, within the resolution of the records, with the onset of a 2°C warming over 2°Coverthe150kyrimmediatelypriortobothrapidd18Oexcursions.However,theonsetofeachofthesephasesoficegrowthissynchronous,withintheresolutionoftherecords,withtheonsetofa2°Cwarmingover150 kyr. We suggest that the warming during these glacial expansions reflect increased greenhouse forcing prompted by a sudden decrease in global chemical weathering rates as Antarctic basement silicate rocks became blanketed by an ice sheet. This represents a negative feedback process that might have operated during major abrupt growth phases of the Antarctic ice sheet.
Paleobiology, 2005
During the Early Jurassic, cyst-forming dinoflagellates began a long-term radiation that would po... more During the Early Jurassic, cyst-forming dinoflagellates began a long-term radiation that would portend ecological importance of these taxa in the pelagic plankton community throughout the rest of the Mesozoic era. The factors that contributed to the evolutionary success of dinoflagellates are poorly understood. Here we examine the relationship between oceanographic and climatic conditions during the Hettangian-Toarcian interval in relation to the radiation of dinoflagellates and other organic-walled phytoplankton taxa in the Tethys Ocean. Our analysis is based on two data sets. The first includes ␦ 13 Ccarb, ␦ 13 Corg, total organic carbon (TOC), and quantitative palynological observations derived from the Mochras Core (Wales, U.K.), which spans the complete Early Jurassic. The second is a coupled Mg/Ca and ␦ 18 O record derived from analyses of belemnite calcite obtained from three sections in northern Spain, covering the upper Sinemurian to Toarcian. From these two data sets we reconstructed the influence of sea level, trophism, temperature, and salinity on dinoflagellate cyst abundance and diversity in northwest Europe. Our results suggest that organic-walled phytoplankton (acritarchs, prasinophytes, and dinoflagellates) diversity increased through the Early Jurassic. The radiation coincides with a long-term eustatic rise and overall increase in the areal extent of continental shelves, a factor critical to cyst germination. On shorter timescales, we observed short bursts of dinoflagellate diversification during the late Sinemurian and late Pliensbachian. The former diversification is consistent with the opening of the Hispanic Corridor during the late Sinemurian, which apparently allowed the pioneer dinoflagellate, Liasidium variabile, to invade the Tethys from the Paleo-Pacific. A true radiation pulse during the late Pliensbachian, with predominantly cold-water taxa, occurred during sea level fall, suggesting that climate change was critical to setting the evolutionary tempo. Our belemnite ␦ 18 O and Mg/Ca data indicate that late Pliensbachian water masses cooled (⌬T ഠ Ϫ6ЊC) and became more saline (⌬S ഠ ϩ2 psu). Cooling episodes during generally warm and humid Early Jurassic climate conditions would have produced stronger winter monsoon northeast trade winds, resulting in hydrographic instability, increased vertical mixing, and ventilation of bottom waters. During the late Pliensbachian, dinoflagellates replaced green algae, including prasinophytes and acritarchs, as primary producers. By producing benthic resting cysts, dinoflagellates may have been better adapted to oxidized ocean regimes. This hypothesis is supported by palynological data from the early Toarcian ocean anoxic event, which was marked by highly stratified anoxic bottom water overlain by lowsalinity, warm surface waters. These conditions were advantageous to green algae, while cyst-producing dinoflagellates temporarily disappeared. Our results suggest that the rise in dinoflagellate diversity later in the Jurassic appears to correspond to deep water ventilation as a result of the opening of the Atlantic seaway, conditions that appear to have simultaneously led to a loss of prasinophyte dominance in the global oceans.
Earth and Planetary Science Letters, 2002
We have generated benthic foraminiferal Mg/Ca records from eastern tropical Atlantic core M16772 ... more We have generated benthic foraminiferal Mg/Ca records from eastern tropical Atlantic core M16772 (3.9 km) and eastern tropical Pacific core TR163-31P (3.2 km) to assess the potential for using benthic Mg-paleothermometry to reconstruct Quaternary bottom water temperature histories. Variations in Mg/Ca records from both the Atlantic and Pacific show a significant correlation with climatic oscillations of the last 330 kyr. Shell Mg/Ca peaks during interglacial episodes, with marine isotope stage MIS) 5e Mg/Ca nearly matching Holocene values in both cores. Lower Mg/Ca values occur during glacial intervals. To estimate temperatures from downcore Mg/Ca, we have augmented the published Cibicidoides sp. Mg/Ca^temperature dataset [Rosenthal et al., Geochim. Cosmochim. Acta 61 (1997) 3633^3643] with new data to include the temperature range of deep waters. Applying the 10.9% change in Mg/Ca per ‡C defined by the expanded calibration to the deep Atlantic data implies glacial^interglacial shifts in deep water temperature of 2^4 ‡C over the last 300 kyr. Temperature estimates are comparable to deep Atlantic temperature changes proposed by Labeyrie et al. [Nature 327 ]. There is greater uncertainty in deriving temperatures from the tropical Pacific core due to a limited Uvigerina spp. core top calibration set; however, glacialî nterglacial temperature oscillations appear to be on the order of 2^3 ‡C. In addition, core TR163-31P records clear millennial-scale Mg/Ca and N 18 O oscillations in MIS 3 corresponding to temperature fluctuations of s 0.5 ‡C. Additional calibration studies are needed to address potential secondary effects on Mg/Ca. ß
Earth and Planetary Science Letters, 2003
The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Nor... more The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Northern Hemisphere Glaciation (NHG). The cause and effects of these changes are still debated. We use a multiproxy approach to determine the relative timing of the closure of the Panama gateway, changes in Atlantic circulation, global cooling and ice sheet growth. Benthic foraminiferal Mg/Ca records from a Pacific and an Atlantic Site have been produced and are interpreted in terms of bottom water temperatures. These Mg-temperature records are combined with published benthic N 13 C, N 18 O and erosion records to reconstruct the flow of proto-North Atlantic Deep Water (proto-NADW) over the past 12 Ma. The results suggest that between 12.5 and 10.5 Ma, and again between about 8.5 and 6 Ma, a nutrient-depleted water mass that was colder (by 1^2 ‡C) and fresher than the intervening deep water mass filled the Atlantic basin. This proto-NADW became warmer (by V1 ‡C) and saltier between 6 and 5 Ma, coincident with the restriction of surface water flow through the Central American Seaway. The Mg-temperature records define a subsequent global cooling trend of V3.5 ‡C between 5 Ma and today. Early NHG in the late Miocene was perhaps related to the formation of the relatively cold, fresh proto-NADW. The formation of the warmer and saltier proto-NADW in the early Pliocene may have initially limited Northern Hemisphere ice growth. However, the increased moisture released at high northern latitudes associated with formation of 'warm' proto-NADW, coupled with the global temperature decrease of deep (and hence polar surface) waters, likely helped initiate the intense NHG of the Plio^Pleistocene. ß
Earth and Planetary Science Letters, 2002
We have generated benthic foraminiferal Mg/Ca records from eastern tropical Atlantic core M16772 ... more We have generated benthic foraminiferal Mg/Ca records from eastern tropical Atlantic core M16772 (3.9 km) and eastern tropical Pacific core TR163-31P (3.2 km) to assess the potential for using benthic Mg-paleothermometry to reconstruct Quaternary bottom water temperature histories. Variations in Mg/Ca records from both the Atlantic and Pacific show a significant correlation with climatic oscillations of the last 330 kyr. Shell Mg/Ca peaks during interglacial episodes, with marine isotope stage (MIS) 5e Mg/Ca nearly matching Holocene values in both cores. Lower Mg/Ca values occur during glacial intervals. To estimate temperatures from downcore Mg/Ca, we have augmented the published Cibicidoides sp. Mg/Ca^temperature dataset [Rosenthal et al., Geochim. Cosmochim. Acta 61 (1997) 3633^3643] with new data to include the temperature range of deep waters. Applying the 10.9% change in Mg/Ca per ‡C defined by the expanded calibration to the deep Atlantic data implies glacial^interglacial shifts in deep water temperature of 2^4 ‡C over the last 300 kyr. Temperature estimates are comparable to deep Atlantic temperature changes proposed by Labeyrie et al. [Nature 327 (1987) 477^482]. There is greater uncertainty in deriving temperatures from the tropical Pacific core due to a limited Uvigerina spp. core top calibration set; however, glacialî nterglacial temperature oscillations appear to be on the order of 2^3 ‡C. In addition, core TR163-31P records clear millennial-scale Mg/Ca and N 18 O oscillations in MIS 3 corresponding to temperature fluctuations of s 0.5 ‡C. Additional calibration studies are needed to address potential secondary effects on Mg/Ca.
Earth and Planetary Science Letters, 2003
The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Nor... more The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Northern Hemisphere Glaciation (NHG). The cause and effects of these changes are still debated. We use a multiproxy approach to determine the relative timing of the closure of the Panama gateway, changes in Atlantic circulation, global cooling and ice sheet growth. Benthic foraminiferal Mg/Ca records from a Pacific and an Atlantic Site have been produced and are interpreted in terms of bottom water temperatures. These Mg-temperature records are combined with published benthic N 13 C, N 18 O and erosion records to reconstruct the flow of proto-North Atlantic Deep Water (proto-NADW) over the past 12 Ma. The results suggest that between 12.5 and 10.5 Ma, and again between about 8.5 and 6 Ma, a nutrient-depleted water mass that was colder (by 1^2 ‡C) and fresher than the intervening deep water mass filled the Atlantic basin. This proto-NADW became warmer (by V1 ‡C) and saltier between 6 and 5 Ma, coincident with the restriction of surface water flow through the Central American Seaway. The Mg-temperature records define a subsequent global cooling trend of V3.5 ‡C between 5 Ma and today. Early NHG in the late Miocene was perhaps related to the formation of the relatively cold, fresh proto-NADW. The formation of the warmer and saltier proto-NADW in the early Pliocene may have initially limited Northern Hemisphere ice growth. However, the increased moisture released at high northern latitudes associated with formation of 'warm' proto-NADW, coupled with the global temperature decrease of deep (and hence polar surface) waters, likely helped initiate the intense NHG of the Plio^Pleistocene.
Ecological Engineering, 1999
Accurate measurements of atmospheric CO 2 concentrations are performed routinely in a variety of ... more Accurate measurements of atmospheric CO 2 concentrations are performed routinely in a variety of experimental settings including open fields and forests, leaf gas-exchange chambers, phytotrons and specialized growth chambers. However, the accurate monitoring of large scale structurally and biologically complex experimental systems, operating as materially closed systems, is not widely reported. Here we report the design elements, material specifications and other details for high precision monitoring of CO 2 in Biosphere 2, a large scale ecologically diverse experimental facility located in Oracle, AZ. The results are used to illustrate how carbon balance in a temporarily isolated subsystem of the facility is used to assess carbon dynamics under different environmental conditions such as variable atmospheric CO 2 levels, temperature, light, and soil moisture. The analytical system described here should be applicable for any settings in which continuous, high accuracy measurements of CO 2 in a complex system are needed for quantitative research.
Geochemistry, Geophysics, Geosystems, 2006
Improving interlaboratory reproducibility (in both precision and accuracy) of Mg/Ca and Sr/Ca det... more Improving interlaboratory reproducibility (in both precision and accuracy) of Mg/Ca and Sr/Ca determination in marine biogenic carbonates is critical in optimizing their utility as paleothermometers. Coupled with a need for uniform sample cleaning practices, there is a need for more exacting methods and procedures across laboratories using varied instrumentation. Here we employ an intensity ratio/matrixeffect correction methodology to a suite of solution standards and biogenic carbonates (foraminifera tests and a gastropod shell) to investigate short-term and long-term Mg/Ca and Sr/Ca precision and accuracy by different instruments: a magnetic-sector inductively coupled plasma-mass spectrometer (ICP-MS) and a radially viewed inductively coupled plasma-optical emission spectrophotometer (ICP-OES). Over an extended 1.0-24.5 mM Ca concentration range, both instruments have significant Ca matrix effects for Mg/Ca and somewhat less for Sr/Ca. Over our working Ca range (1-8 mM Ca), Mg/Ca matrix effects are significant, requiring correction, and Sr/Ca matrix effects are small to negligible, occasionally requiring correction (linear or logarithmic fit) using a suite of matrix standards for both instruments. The short-term (intrarun) precision for a suite of solution standards is <0.2% (1s %RSD) for Mg/Ca and Sr/Ca for both instruments. A long-term (interrun) precision of <0.9% is demonstrated for Mg/Ca and <0.6% for Sr/Ca on both instruments. The accuracy of measured Mg/Ca and Sr/Ca values for short-and long-term standards is similar on both instruments at better than 1 ± 0.5%, on par with our long-term precision. An interinstrument comparison of the same measured suite of biogenic carbonates demonstrates that after accounting for matrix effects, data generated on either instrument are essentially interchangeable (within analytical precision) to a high degree of fidelity.
The Journal of …, 2010
Geochemical analyses of the carbonate tests calcified by foraminifera have provided much of the f... more Geochemical analyses of the carbonate tests calcified by foraminifera have provided much of the foundation for reconstructions of past ocean and climate conditions, and for chemostratigraphy. In particular, reconstructions of climate history (including temperature, ...
Analytical Chemistry, 1999
A new method was developed for rapid and precise simultaneous determination of Mg/Ca, Sr/Ca, Mn/C... more A new method was developed for rapid and precise simultaneous determination of Mg/Ca, Sr/Ca, Mn/Ca, Cd/Ca, Ba/Ca and U/Ca ratios in foraminiferal shells using sector field inductively coupled plasma mass spectrometry (ICPMS). Element/calcium ratios were determined directly from intensity ratios using external, matrixmatched standard to correct for instrumental mass discrimination. Because of large differences in the abundance of chemical constituents of the foraminiferal shell, major elemental ratios were determined in analog mode (using 24 Mg, 43 Ca, 44 Ca, 55 Mn, and 88 Sr) whereas trace elemental ratios were determined in pulse-counting mode (using 111 Cd, 138 Ba, 238 U, and the low-abundance 46 Ca isotope). Matrix-induced variations in mass discrimination over a calcium concentration range of 2.0-24.5 mM were observed only for Mg/Ca and Cd/Ca ratios. However, these effects are negligible if the samples and standard calcium concentration are within a factor of 2-3. Multiratio method reproducibility was better than previously reported for other ICPMS methods yielding precision (1σ) of Sr/Ca ) 0.45%; Mg/Ca ) 0.45%, Mn/Ca ) 0.8%, Cd/ Ca ) 1.7%, Ba/Ca ) 0.7%, and U/Ca ) 1.4% for foraminifera samples as small as 25 µg. Using this approach for a single-ratio analysis, Sr/Ca ratios were determined with precision of 0.06% (1σ) on carbonate samples as small as a single foraminifera shell (<10 µg). The new method is more sensitive, more precise, and simpler to use than previously available ICPMS techniques. It provides an efficient tool for simultaneous determination of several elemental ratios of paleoceanographic interest in a single foraminiferal sample, thereby reducing overall sample size requirement and analysis time.
Geochimica Et Cosmochimica Acta, 2002
... Climate proxies from Sr/Ca of coccolith calcite: calibrations from continuous culture of Emil... more ... Climate proxies from Sr/Ca of coccolith calcite: calibrations from continuous culture of Emiliania huxleyi. ... primary producers, the trace element chemistry of their shells may provide different information than that of foraminifera or corals commonly used in paleoceanographic ...
Geochimica Et Cosmochimica Acta, 1993
This work is an assessment of the effects of seawater salinity and temperature on the incorporati... more This work is an assessment of the effects of seawater salinity and temperature on the incorporation of fluoride into calcitic shells of planktonic foraminifera and of the subsequent modification of shell chemistry by postdepositional dissolution. A strong correlation between the fluoride content of most planktonic species and their calcification depth was observed, deeper-calcifying foraminifera have lower fluoride content and heavier '*O composition, perhaps suggesting a temperature control on the partition coefficient. However, species deviations from this general trend and the absence of correlation between fluoride and sea-surface temperature within an individual species suggest that the coprecipitation of fluoride in foraminiferal calcite is more strongly controlled by biological processes rather than by simple chemical relationships. Foraminiferal fluoride shows weak or no correlation with sea-surface salinity.
Geochimica Et Cosmochimica Acta, 1997
Earth and Planetary Science Letters, 1995
Geochemistry Geophysics Geosystems, 2003
1] We have generated a new high-resolution record of variations in planktonic foraminiferal oxyge... more 1] We have generated a new high-resolution record of variations in planktonic foraminiferal oxygen isotopes (d 18 O) and Mg/Ca from a sediment core (IMAGES 97-2141) in the Sulu Sea located in the Philippine archipelago of western tropical Pacific. This record reveals distinct, suborbital-scale d 18 O changes, most notably during Marine Isotope Stage 3 (MIS3) ($30,000 to 60,000 years B.P.). The amplitudes of these d 18 O fluctuations (0.4 to 0.7%) exceed that which can be attributed to sea level changes and must be due to changes in sea surface conditions. In the same interval, variations in planktonic foraminifera Mg/Ca suggest that suborbital surface ocean temperature variations of 1 to 1.5°C in the Sulu Sea were not in phase with d 18 O. Combined, this evidence indicates that the MIS3 millennial d 18 O events in the Sulu Sea were primarily the result of changes in surface water salinity, which today is directly related to the East Asian Monsoon (EAM) and its influence on the balance between surface water contributions from the South China Sea and Western Pacific Warm Pool (WPWP). Within dating uncertainties the MIS3 Sulu Sea d 18 O suborbital variability indicates that times of fresher surface conditions in the Sulu Sea coincide with similar conditions in the WPWP and also with intensifications of the summer EAM as recorded in the U-Th dated Chinese (Hulu Cave) speleothem d 18 O record and thus by inference with interstadials in the Greenland Ice core records. Combined, these results indicate that pronounced suborbital variability in the summer EAM and Intertropical Convergence Zone (ITCZ) during MIS3 was tightly coupled with climate conditions in the northern high latitudes.
Geochemistry Geophysics Geosystems, 2003
1] A detailed record of planktic d 18 O from a sediment core in the Sulu Sea, located between the... more 1] A detailed record of planktic d 18 O from a sediment core in the Sulu Sea, located between the South China Sea and the western Pacific warm pool, reveals that for the past 400 kyr (1 kyr = 1000 years), d 18 O variability on orbital timescales is similar to that caused by changes in ice volume alone. This result indicates that in the Sulu Sea, temperature-driven changes in planktic d 18 O on orbital times scales were generally compensated for by the effects of sea level and changes in seasonal monsoon intensity on the local freshwater budget, as well as by other changes in the tropical hydrologic cycle and their attendant effects on surface water d 18 O. Increased freshening of the western tropical Pacific warm pool is reminiscent of La Niña conditions. However, we argue that the mean tropical climate state was not more La Niña-like than today on broader spatial scales. Suborbital variability occurred in the Sulu Sea throughout the past 400 kyr, suggesting little sensitivity to ice volume or to glacial-interglacial changes in tropical hydrology. Variations on 4-10 kyr timescales appear to be linked to those in the North Atlantic region, suggesting a common forcing of that variability. We suggest that Sulu Sea salinity variations were a response to suborbital climate variability in the North Atlantic region, transmitted via changes in the intensity of the East Asian summer monsoon. We suggest that a North Atlantic origin of that tropical suborbital variability can be reconciled with weak glacial amplification in the tropics if the tropical response is nonlinear.
1] Paired benthic foraminiferal trace metal and stable isotope records have been constructed from... more 1] Paired benthic foraminiferal trace metal and stable isotope records have been constructed from equatorial Pacific Ocean Drilling Program Site 1218. The records include the two largest abrupt (<1 Myr) increases in the Cenozoic benthic oxygen isotope record: Oi-1 in the earliest Oligocene ($34 Ma) and Mi-1 in the earliest Miocene ($23 Ma). The paired Mg/Ca and oxygen isotope records are used to calculate seawater d 18 O (dw). Calculated dw suggests that a large Antarctic ice sheet formed during Oi-1 and subsequently fluctuated throughout the Oligocene on both short (<0.5 Myr) and long (2-3 Myr) timescales, between about 50 and 100% of its maximum earliest Oligocene size. The magnitudes of these fluctuations are consistent with estimates of sea level derived from sequence stratigraphy. The transient expansion of the Antarctic ice sheet at Mi-1 is marked in the benthic d 18 O record by two positive excursions between 23.7 and 22.9 Ma, each with a duration of 200-300 kyr. Bottom water temperatures decreased by 2°Coverthe150kyrimmediatelypriortobothrapidd18Oexcursions.However,theonsetofeachofthesephasesoficegrowthissynchronous,withintheresolutionoftherecords,withtheonsetofa2°Cwarmingover2°C over the 150 kyr immediately prior to both rapid d 18 O excursions. However, the onset of each of these phases of ice growth is synchronous, within the resolution of the records, with the onset of a 2°C warming over 2°Coverthe150kyrimmediatelypriortobothrapidd18Oexcursions.However,theonsetofeachofthesephasesoficegrowthissynchronous,withintheresolutionoftherecords,withtheonsetofa2°Cwarmingover150 kyr. We suggest that the warming during these glacial expansions reflect increased greenhouse forcing prompted by a sudden decrease in global chemical weathering rates as Antarctic basement silicate rocks became blanketed by an ice sheet. This represents a negative feedback process that might have operated during major abrupt growth phases of the Antarctic ice sheet.
Paleobiology, 2005
During the Early Jurassic, cyst-forming dinoflagellates began a long-term radiation that would po... more During the Early Jurassic, cyst-forming dinoflagellates began a long-term radiation that would portend ecological importance of these taxa in the pelagic plankton community throughout the rest of the Mesozoic era. The factors that contributed to the evolutionary success of dinoflagellates are poorly understood. Here we examine the relationship between oceanographic and climatic conditions during the Hettangian-Toarcian interval in relation to the radiation of dinoflagellates and other organic-walled phytoplankton taxa in the Tethys Ocean. Our analysis is based on two data sets. The first includes ␦ 13 Ccarb, ␦ 13 Corg, total organic carbon (TOC), and quantitative palynological observations derived from the Mochras Core (Wales, U.K.), which spans the complete Early Jurassic. The second is a coupled Mg/Ca and ␦ 18 O record derived from analyses of belemnite calcite obtained from three sections in northern Spain, covering the upper Sinemurian to Toarcian. From these two data sets we reconstructed the influence of sea level, trophism, temperature, and salinity on dinoflagellate cyst abundance and diversity in northwest Europe. Our results suggest that organic-walled phytoplankton (acritarchs, prasinophytes, and dinoflagellates) diversity increased through the Early Jurassic. The radiation coincides with a long-term eustatic rise and overall increase in the areal extent of continental shelves, a factor critical to cyst germination. On shorter timescales, we observed short bursts of dinoflagellate diversification during the late Sinemurian and late Pliensbachian. The former diversification is consistent with the opening of the Hispanic Corridor during the late Sinemurian, which apparently allowed the pioneer dinoflagellate, Liasidium variabile, to invade the Tethys from the Paleo-Pacific. A true radiation pulse during the late Pliensbachian, with predominantly cold-water taxa, occurred during sea level fall, suggesting that climate change was critical to setting the evolutionary tempo. Our belemnite ␦ 18 O and Mg/Ca data indicate that late Pliensbachian water masses cooled (⌬T ഠ Ϫ6ЊC) and became more saline (⌬S ഠ ϩ2 psu). Cooling episodes during generally warm and humid Early Jurassic climate conditions would have produced stronger winter monsoon northeast trade winds, resulting in hydrographic instability, increased vertical mixing, and ventilation of bottom waters. During the late Pliensbachian, dinoflagellates replaced green algae, including prasinophytes and acritarchs, as primary producers. By producing benthic resting cysts, dinoflagellates may have been better adapted to oxidized ocean regimes. This hypothesis is supported by palynological data from the early Toarcian ocean anoxic event, which was marked by highly stratified anoxic bottom water overlain by lowsalinity, warm surface waters. These conditions were advantageous to green algae, while cyst-producing dinoflagellates temporarily disappeared. Our results suggest that the rise in dinoflagellate diversity later in the Jurassic appears to correspond to deep water ventilation as a result of the opening of the Atlantic seaway, conditions that appear to have simultaneously led to a loss of prasinophyte dominance in the global oceans.
Earth and Planetary Science Letters, 2002
We have generated benthic foraminiferal Mg/Ca records from eastern tropical Atlantic core M16772 ... more We have generated benthic foraminiferal Mg/Ca records from eastern tropical Atlantic core M16772 (3.9 km) and eastern tropical Pacific core TR163-31P (3.2 km) to assess the potential for using benthic Mg-paleothermometry to reconstruct Quaternary bottom water temperature histories. Variations in Mg/Ca records from both the Atlantic and Pacific show a significant correlation with climatic oscillations of the last 330 kyr. Shell Mg/Ca peaks during interglacial episodes, with marine isotope stage MIS) 5e Mg/Ca nearly matching Holocene values in both cores. Lower Mg/Ca values occur during glacial intervals. To estimate temperatures from downcore Mg/Ca, we have augmented the published Cibicidoides sp. Mg/Ca^temperature dataset [Rosenthal et al., Geochim. Cosmochim. Acta 61 (1997) 3633^3643] with new data to include the temperature range of deep waters. Applying the 10.9% change in Mg/Ca per ‡C defined by the expanded calibration to the deep Atlantic data implies glacial^interglacial shifts in deep water temperature of 2^4 ‡C over the last 300 kyr. Temperature estimates are comparable to deep Atlantic temperature changes proposed by Labeyrie et al. [Nature 327 ]. There is greater uncertainty in deriving temperatures from the tropical Pacific core due to a limited Uvigerina spp. core top calibration set; however, glacialî nterglacial temperature oscillations appear to be on the order of 2^3 ‡C. In addition, core TR163-31P records clear millennial-scale Mg/Ca and N 18 O oscillations in MIS 3 corresponding to temperature fluctuations of s 0.5 ‡C. Additional calibration studies are needed to address potential secondary effects on Mg/Ca. ß
Earth and Planetary Science Letters, 2003
The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Nor... more The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Northern Hemisphere Glaciation (NHG). The cause and effects of these changes are still debated. We use a multiproxy approach to determine the relative timing of the closure of the Panama gateway, changes in Atlantic circulation, global cooling and ice sheet growth. Benthic foraminiferal Mg/Ca records from a Pacific and an Atlantic Site have been produced and are interpreted in terms of bottom water temperatures. These Mg-temperature records are combined with published benthic N 13 C, N 18 O and erosion records to reconstruct the flow of proto-North Atlantic Deep Water (proto-NADW) over the past 12 Ma. The results suggest that between 12.5 and 10.5 Ma, and again between about 8.5 and 6 Ma, a nutrient-depleted water mass that was colder (by 1^2 ‡C) and fresher than the intervening deep water mass filled the Atlantic basin. This proto-NADW became warmer (by V1 ‡C) and saltier between 6 and 5 Ma, coincident with the restriction of surface water flow through the Central American Seaway. The Mg-temperature records define a subsequent global cooling trend of V3.5 ‡C between 5 Ma and today. Early NHG in the late Miocene was perhaps related to the formation of the relatively cold, fresh proto-NADW. The formation of the warmer and saltier proto-NADW in the early Pliocene may have initially limited Northern Hemisphere ice growth. However, the increased moisture released at high northern latitudes associated with formation of 'warm' proto-NADW, coupled with the global temperature decrease of deep (and hence polar surface) waters, likely helped initiate the intense NHG of the Plio^Pleistocene. ß