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  • 1
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    PANGAEA
    In:  Supplement to: Lynch-Stieglitz, Jean; Curry, William B; Slowey, Niall C (1999): A geostrophic transport estimate for the Florida Current from the oxygen isotope composition of benthic foraminifera. Paleoceanography, 14(3), 360-373, https://doi.org/10.1029/1999PA900001
    Publication Date: 2020-01-17
    Description: We present a new method for the quantitative reconstruction of upper ocean flows for during times in the past. For the warm (T〉5°C) surface ocean, density can be accurately reconstructed from calcite precipitated in equilibrium with seawater, as both of these properties increase with decreasing temperature and increasing salinity. Vertical density profiles can be reconstructed from the oxygen isotopic composition of benthic foraminifera. The net volume transport between two vertical density profiles can be calculated using the geostrophic method. Using benthic foraminifera from surface sediment samples from either side of the Florida Straits (Florida Keys and Little Bahama Bank), we reconstruct two vertical density profiles and calculate a volume transport of 32 Sv using this method. This agrees well with estimates from physical oceanographic methods of 30-32 Sv for the mean annual volume transport. We explore the sensitivity of this technique to various changes in the relationship between temperature and salinity as well as salinity and the oxygen isotopic composition of seawater.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 2
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    PANGAEA
    In:  Supplement to: Schmidt, Matthew W; Weinlein, William A; Marcantonio, Franco; Lynch-Stieglitz, Jean (2012): Solar forcing of Florida Straits surface salinity during the early Holocene. Paleoceanography, 27(3), PA3204, https://doi.org/10.1029/2012PA002284
    Publication Date: 2020-01-17
    Description: Previous studies showed that sea surface salinity (SSS) in the Florida Straits as well as Florida Current transport covaried with changes in North Atlantic climate over the past two millennia. However, little is known about earlier Holocene hydrographic variability in the Florida Straits. Here, we combine Mg/Ca-paleothermometry and stable oxygen isotope measurements on the planktonic foraminifera Globigerinoides ruber (white variety) from Florida Straits sediment core KNR166-2 JPC 51 (24° 24.70' N, 83° 13.14' W, 198 m deep) to reconstruct a high-resolution (~25 yr/sample) early to mid Holocene record of sea surface temperature and d18OSW (a proxy for SSS) variability. After removing the influence of global d18OSW change due to continental ice volume variability, we find that early Holocene SSS enrichments are associated with increased evaporation/precipitation ratios in the Florida Straits during periods of reduced solar forcing, increased ice rafted debris in the North Atlantic and the development of more permanent El Niño-like conditions in the eastern equatorial Pacific. When considered with previous high-resolution reconstructions of Holocene tropical atmospheric circulation changes, our results provide evidence that variations in solar forcing over the early Holocene had a significant impact on the global tropical hydrologic cycle.
    Type: Dataset
    Format: text/tab-separated-values, 35 data points
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  • 3
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    PANGAEA
    In:  Supplement to: Lynch-Stieglitz, Jean; Schmidt, Matthew W; Curry, William B (2011): Evidence from the Florida Straits for Younger Dryas ocean circulation changes. Paleoceanography, 26(1), PA1205, https://doi.org/10.1029/2010PA002032
    Publication Date: 2020-01-17
    Description: The waters passing through the Florida Straits today reflect both the western portion of the wind-driven subtropical gyre and the northward flow of the upper waters which cross the equator, compensating North Atlantic Deep Water export as part of the large-scale Atlantic meridional overturning circulation. It has been postulated from various lines of evidence that the overturning circulation was weaker during the Younger Dryas cold event of the last deglaciation. We show here that the contrast in the oxygen isotopic composition of benthic foraminiferal tests across the Florida Current is reduced during the Younger Dryas. This most likely reflects a decrease in the density gradient across the channel and a decrease in the vertical shear of the Florida Current. This reduced shear is consistent with the postulated reduction in the Atlantic meridional overturning circulation. We find that the onset of this change in density structure and flow at the start of the Younger Dryas is very abrupt, occurring in less than 70 years.
    Type: Dataset
    Format: text/tab-separated-values, 350 data points
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  • 4
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    PANGAEA
    In:  Supplement to: Koutavas, Athanasios; Lynch-Stieglitz, Jean (2003): Glacial-interglacial dynamics of the eastern equatorial Pacific cold tongue-Intertropical Convergence Zone system reconstructed from oxygen isotope records. Paleoceanography, 18(4), 1089, https://doi.org/10.1029/2003PA000894
    Publication Date: 2020-01-17
    Description: We use planktonic oxygen isotope (d18O) records spanning the last 30,000 years (kyr) to constrain the magnitude and spatial pattern of glacial cooling in the upwelling environment of the eastern equatorial Pacific (EEP). Fourteen new downcore d18O records were obtained from surface-dwelling planktonic foraminifera Globigerinoides sacculifer and Globigerinoides ruber in eight cores from the upwelling tongue of the EEP. All sites have sedimentation rates exceeding 5 cm/kyr and, with one exception, lie above the modern depth of the foraminiferal lysocline. Sites directly underlying the cool band of upwelling immediately south of the equator record mean late Holocene (LH)-Last Glacial Maximum (LGM) d18O amplitudes ranging between 1.0 and 1.3 per mil. We estimate that mean sea surface temperatures (SST) in this region during the LGM were on average 1.5 ± 0.5°C lower than the LH. Larger d18O amplitudes are observed in sites north of the equator, indicating a spatial pattern of reduced meridional SST gradient across the equator during the LGM. This result is supported by comparison of Mg/Ca SST reconstructions from two sites straddling the equator. We interpret the reduction of this gradient during the LGM as evidence for a less intense cold tongue-Intertropical Convergence Zone (ITCZ) frontal system, a more southerly position of the ITCZ, and weaker southeast equatorial trades in the EEP.
    Type: Dataset
    Format: text/tab-separated-values, 215 data points
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  • 5
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 499 data points
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  • 6
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    PANGAEA
    In:  Supplement to: Matsumoto, Katsumi; Lynch-Stieglitz, Jean (1999): Similar glacial and Holocene deep water circulation inferred from southeast Pacific benthic foraminiferal carbon isotope composition. Paleoceanography, 14(2), 149-163, https://doi.org/10.1029/1998PA900028
    Publication Date: 2020-01-17
    Description: We present Holocene and last glacial maximum (LGM) oxygen and carbon isotope measurements on Planulina wuellerstorfi in six southeast Pacific cores. Sedimentation rates are low in this part of the ocean, and measurements were made on individual foraminiferal shells in order to identify the Holocene and glacial individuals on the basis of their extreme d18O. The new d13C data were combined with previous P. wuellerstorfi data for interpretation of global thermohaline circulation. Data from the Southern Ocean were examined closely for regional coherency and a few anomalous d13C values suspected of having productivity overprint were removed. The resulting global d13C distributions and gradients indicate that the deep water circulation was similar during the Holocene and LGM. This interpretation brings d13C data to a better agreement with Cd/Ca data and marks a sharp contrast with a widely held view based on d13C measurements that the glacial Southern Ocean was the terminus of the thermohaline circulation. The proposed presence of glacial North Atlantic Deep Water does not necessarily contradict the postulated presence of Glacial North Atlantic Intermediate Water.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 7
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 36 data points
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  • 8
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    PANGAEA
    In:  Supplement to: Lynch-Stieglitz, Jean; Curry, William B; Lund, David C (2009): Florida Straits density structure and transport over the last 8000 years. Paleoceanography, 24(3), PA3209, https://doi.org/10.1029/2008PA001717
    Publication Date: 2020-01-17
    Description: The density structure across the Florida Straits is reconstructed for the last 8000 years from oxygen isotope measurements on foraminifera in sediment cores. The oxygen isotope measurements suggest that the density contrast across the Florida Current increased over this time period. The magnitude of this change corresponds to an increase in the geostrophic transport referenced to 800 m water depth of 4 sverdrups (Sv) over the last 8000 years. The spatial and seasonal distribution of incoming solar radiation due to changes in the Earth's orbit has caused systematic changes in the atmospheric circulation, including a southward migration of the Intertropical Convergence Zone over the last 8000 years. These changes in atmospheric circulation and the associated wind-driven currents of the upper ocean could readily account for a 4 Sv increase in the strength of the Florida Current. We see no evidence in our data for dramatic changes in the strength of the Atlantic Meridional Overturning Circulation over this time period.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 9
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    PANGAEA
    In:  Supplement to: Völpel, Rike; Mulitza, Stefan; Paul, A; Lynch-Stieglitz, Jean; Schulz, Michael (2019): Water Mass Versus Sea Level Effects on Benthic Foraminiferal Oxygen Isotope Ratios in the Atlantic Ocean During the LGM. Paleoceanography and Paleoclimatology, 34(1), 98-121, https://doi.org/10.1029/2018PA003359
    Publication Date: 2020-01-17
    Description: Depth transects of benthic foraminiferal oxygen isotopes from the Atlantic Ocean show that glacial‐interglacial changes are larger at deep (〉 ~2000 m) than at intermediate water levels. Our model results suggest that the smaller changes in the upper 1000 m of the water column are a result of the glacial sea‐level lowering of about 120 m, leading to warmer temperatures of around 1 °C and hence a smaller glacial‐interglacial stable oxygen isotope difference. In contrast, a shoaling of the water‐mass boundary to ~2000 m water depth between the northern source and southern source water is accompanied by the expansion of a cold (close to the freezing point) southern source water in the abyssal ocean, increasing the oxygen isotope values of benthic foraminifera from the LGM in the deep Atlantic. These two effects explain the different amplitudes of glacial‐interglacial stable oxygen isotope differences in the upper and deeper water column of the Atlantic Ocean.
    Type: Dataset
    Format: application/zip, 5 datasets
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  • 10
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    PANGAEA
    In:  Supplement to: Schmidt, Matthew W; Lynch-Stieglitz, Jean (2011): Florida Straits deglacial temperature and salinity change: Implications for tropical hydrologic cycle variability during the Younger Dryas. Paleoceanography, 26(4), PA4205, https://doi.org/10.1029/2011PA002157
    Publication Date: 2020-01-17
    Description: The prevailing paradigm of abrupt climate change holds that rapid shifts associated with the most extreme climate swings of the last glacial cycle were forced by changes in the strength and northward extension of Atlantic Meridional Overturning Circulation (AMOC), resulting in an abrupt reorganization of atmospheric circulation patterns with global teleconnections. To determine the timing of tropical Atlantic atmospheric circulation changes over the past 21 ka BP, we reconstruct high resolution sea surface temperature and d18OSW (a proxy for surface salinity) records based on Mg/Ca ratios and oxygen isotope measurements in the planktonic foraminifera Globigerinoides ruber from a sediment core located on the western margin of the Florida Straits. As a proxy for meltwater discharge influence on Florida Straits surface water salinity, we also measured Ba/Ca ratios in G. ruber from the same core. Results show that riverine influence on Florida Straits surface water started by 17.2 ka BP and ended by 13.6 ka BP, 600 years before the start of the Younger Dryas (YD) cold interval. The initiation of the YD is marked by an abrupt increase in Florida Straits d18OSW values, indicating a shift to elevated sea surface salinity occurring in 130 years, most likely resulting from increased regional aridity and/or reduced precipitation. In order to resolve the timing of tropical atmospheric circulation change relative to AMOC variability across this transition, we compare the timing of surface water changes to a recently published record of Florida Current variability in the same core reconstructed from benthic oxygen isotope measurements. We find synchronous changes in atmospheric and ocean circulation on the transition into the YD, consistent with an abrupt reduction in AMOC as the driver of tropical Atlantic atmospheric circulation change at this time.
    Type: Dataset
    Format: text/tab-separated-values, 111 data points
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