# Seawater Sr/Ca in Florida and Around the World between 2016-2020 CE #----------------------------------------------------------------------- # World Data Service for Paleoclimatology, Boulder # and # NOAA Paleoclimatology Program #----------------------------------------------------------------------- # Template Version 4.0 # Encoding: UTF-8 # NOTE: Please cite original publication, NOAA Landing Page URL, dataset and publication DOIs (where available), and date accessed when using downloaded data. # If there is no publication information, please cite investigator, study title, NOAA Landing Page URL, and date accessed. # # Description/Documentation lines begin with '#' followed by a space # Data lines have no '#' # # NOAA_Landing_Page: https://www.ncei.noaa.gov/access/paleo-search/study/41080 # Landing_Page_Description: NOAA Landing Page of this file's parent study, which includes all study metadata. # # Study_Level_JSON_Metadata: https://www.ncei.noaa.gov/pub/data/metadata/published/paleo/json/noaa-coral-41080.json # Study_Level_JSON_Description: JSON metadata of this data file's parent study, which includes all study metadata. # # Data_Type: Corals and Sclerosponges # # Dataset_DOI: 10.25921/jd8r-nc90 # # Science_Keywords: biogeochemical cycles #--------------------------------------- # Resource_Links # # Data_Download_Resource: https://www.ncei.noaa.gov/pub/data/paleo/coral/multiregion/kilbourne2025/kilbourne2025-24hr.txt # Data_Download_Description: NOAA Template File; 24 Hour Caribbean Sr/Ca Data # #--------------------------------------- # Contribution_Date # Date: 2025-03-13 #--------------------------------------- # File_Last_Modified_Date # Date: 2025-09-12 #--------------------------------------- # Title # Study_Name: Seawater Sr/Ca in Florida and Around the World between 2016-2020 CE #--------------------------------------- # Investigators # Investigators: Kilbourne, K.H.; Schijf, Johan; Hughes, Hunter P.; Khare, Agraj #--------------------------------------- # Description_Notes_and_Keywords # Description: Seawater Sr/Ca to complement coral-based paleoclimate efforts. The study spanned 2016-2020 in the Middle Florida Keys with the grid extending from shore to the forereef area about 6km offshore, along about 11km of coastline. Samples in Khare et al., 2022 were sampled collected by hand from the surface and at the bottom by diver in the winter and summer in the Florida Keys. Samples of opportunity were collected by hand from a variety of locations in the Pacific, Indian and Atlantic Oceans. Samples from Hughes et al., 2025 were collected at 4 sites in the Florida Keys spanning across the shelf from Florida Bay to the forereef area via osmotic pumps into teflon tubing that was subsequently subsampled and analyzed in the laboratory. OSMO sampler dates are based on known days of pump deployment and retrieval, sample volume and pump rates. Other samples were collected on known dates indicated. # Provided Keywords: strontium, trace element, seawater chemistry, Sr/Ca #--------------------------------------- # Publication # Authors: Hughes, Hunter P., Johan Schijf, K. Halimeda Kilbourne # Published_Date_or_Year: 2025 # Published_Title: High-resolution annual cycles of the Sr/Ca ratio in Florida Bay seawater sampled with osmotic pumps # Journal_Name: Paleoceanography and Paleoclimatology # Volume: 40 # Edition: # Issue: 9 # Pages: # Report_Number: e2025PA005168 # DOI: 10.1029/2025PA005168 # Online_Resource: # Full_Citation: # Abstract: Coral skeletal Sr/Ca ratios are a commonly used paleotemperature proxy that relies on stable seawater Sr/Ca ratios (Rsw). Recent observations call this assumption into question at some locations, particularly in the Florida Keys, USA. We collected Rsw time series data for 4 years from the Middle Keys with about weekly resolution, as well as several 24-hr time series from coral reef sites throughout the Caribbean, to quantify the magnitude and mode of Rsw variability and to assess its likely impact on coral Sr/Ca-based paleoclimate reconstructions. Continuous seawater samples were collected with four bottom-mounted osmotic pumps placed on a transect from inside Florida Bay to approximately 10 km offshore. In Florida Bay, Rsw displays annual cycles with high values in the summer and an amplitude of 0.4–0.5 mmol/mol that attenuates and becomes less periodic with increasing distance from the coast. We propose that this seawater Sr/Ca cycle may be due to a seasonal biogeochemical process related to the precipitation and dissolution of CaCO3 in Florida Bay, with the signal carried onto the shelf through mixing. The annual Rsw cycle can explain the low Sr/Ca–SST slopes that have been reported in local corals. Pseudo-coral Sr/Ca calculations indicate that Rsw causes enhanced uncertainty in reconstructed SST, even at the site 10 km offshore. The 24-hr time series show smaller diurnal variability in seawater Sr/Ca that appears to reflect local tides and hydrography, suggesting a similar potential for aberrant coral Sr/Ca–SST calibrations at other reef locations. #--------------------------------------- # Publication # Authors: Agraj Khare, Hunter P. Hughes, K. Halimeda Kilbourne, and Johan Schijf # Published_Date_or_Year: 2022 # Published_Title: Seasonal variations of the seawater Sr/Ca ratio across the Florida Keys Reef Tract # Journal_Name: Geochemistry, Geophysics, Geosystems # Volume: 24 # Edition: # Issue: 3 # Pages: # Report_Number: e2022GC010728 # DOI: 10.1029/2022GC010728 # Online_Resource: # Full_Citation: # Abstract: A surface seawater Sr/Ca ratio dataset was assembled across a section of the Florida Keys Reef Tract, to uncover variability that might explain previously reported anomalies in local calibrations of the coral aragonite Sr/Ca paleotemperature proxy. Samples were collected twice per year on a grid of 54 sites, from September of 2016 until January of 2020. The ~325 km2 grid extended from the shore out to the forereef and from the east end of Long Key to the west end of Marathon. Seawater Sr/Ca ratios were measured using a newly designed ICP-AES method with a long-term precision of better than 0.2%, with data normalized against an in-house seawater reference, quantified by ICP-MS. #--------------------------------------- # Publication # Authors: Agraj Khare, Hunter P. Hughes, K. Halimeda Kilbourne, and Johan Schijf # Published_Date_or_Year: 2021 # Published_Title: An ICP-AES method for routine high-precision measurement of seawater Sr/Ca ratios to validate coral paleothermometry calibrations # Journal_Name: Limnology and Oceanography Methods # Volume: 19 # Edition: # Issue: # Pages: 416-430 # Report_Number: # DOI: 10.1002/lom3.10434 # Online_Resource: # Full_Citation: # Abstract: A new ICP-AES method is presented for rapid and routine analysis of Sr/Ca molar ratios in seawater, with a long-term precision of <0.2%. It is an adaptation of a method widely employed for the analysis of coral aragonite Sr/Ca ratios in marine paleothermometry studies, which are based on the assumption that the seawater Sr/Ca ratio is constant in space and time. While prior studies have shown variations of up to 1% with depth, smaller variations at the ocean surface are generally accounted for via empirical, species-specific calibrations of coral Sr/Ca vs. temperature. We found Sr/Ca variations in some coastal waters to be even larger, with distinct periodicity, complicating this approach. Whereas the high precision necessary for measurements of seawater Sr/Ca has previously relied on advanced mass spectrometry, long analysis times, and expensive isotopic spikes, our method uses more accessible instrumentation and is both time- and cost-saving. The intricate composition of seawater, relative to coral aragonite solutions, requires an intensity ratio calibration technique combined with rigorous normalization to a suitable seawater standard. Key aspects of our method are discussed, including choice of wavelengths, instrumental parameters, accuracy, precision, and matrix effects. Special attention is given to the need for a certified seawater Sr/Ca reference standard, which does not presently exist. Analytical validation is provided by concurrent sharp gradients in Sr/Ca and d18O, coinciding with the Florida landfall of hurricane Irma, as recorded at near-daily resolution in a continuous seawater sample collected with an osmotic pump. #--------------------------------------- # Funding_Agency # Funding_Agency_Name: US National Science Foundation # Grant: OCE 1459636, OCE 1829385 #--------------------------------------- # Site_Information # Site_Name: Northeast Caribbean Sea # Location: Caribbean Sea # Northernmost_Latitude: 24.8265 # Southernmost_Latitude: 18.7386 # Easternmost_Longitude: -64.3091 # Westernmost_Longitude: -80.8145 # Elevation_m: #--------------------------------------- # Data_Collection # Collection_Name: 24Hr Caribbean Sr/Ca Kilbourne2025 # First_Year: 2013 # Last_Year: 2017 # Time_Unit: year Common Era # Core_Length_m: # Parameter_Keywords: trace metals # Notes: Filtered water samples taken by syringe with a 0.2 micron filter into low density polyethylene bottles and kept in the cool dark (sample refrigerator) before analysis via ICP-OES. All sampling in the Florida Keys National Marine Santuary was performed under permits FKNMS-2016-099, FKNMS-2016-099-A2 and FKNMS-2016-099-A3 issued by the National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries #--------------------------------------- # Chronology_Information # Chronology: # OSMO sampler dates are based on known days of pump deployment and retrieval, sample volume and pump rates. Other samples were collected on known dates indicated. #--------------------------------------- # Variables # PaST_Thesaurus_Download_Resource: https://www.ncei.noaa.gov/access/paleo-search/skos/past-thesaurus.rdf # PaST_Thesaurus_Download_Description: Paleoenvironmental Standard Terms (PaST) Thesaurus terms, definitions, and relationships in SKOS format. # # Data variables follow that are preceded by "##" in columns one and two. # Variables list, one per line, shortname-tab-var components: what, material, error, units, seasonality, data type, detail, method, C or N for Character or Numeric data) # ## Location notes,,,,,instrumental,,,C,Loblolly is Loblolly Beach Anegada British Virgin islands; Punta Cana is Punta Cana Dominican Republic; and KML is the Keys Marine Laboratory on the north side of Long Key Florida ## Latitude latitude,,,degree north,,instrumental,,,N, ## Longitude longitude,,,degree east,,instrumental,,,N, ## Date collection date,,,day of year,,instrumental,,,C,calendar date of the sample collection (mm/dd/yyyy) ## localtime notes,,,hour,,instrumental,,,N,local time in 24h notation ## Sr/Ca strontium/calcium,sea water,,millimole per mole,,instrumental,,inductively-coupled plasma atomic emission spectroscopy,N,For a description of the analytical methods see Khare et al 2021 (L and O Methods) ## Sr/Ca_SE strontium/calcium,sea water,one standard error,millimole per mole,,instrumental,,inductively-coupled plasma atomic emission spectroscopy,N,replicates are part of the method; this is the standard error of at least 5 replicate measurements during analysis #------------------------ # Data: # Data lines follow (have no #) # Data line format - tab-delimited text, variable short name as header # Missing_Values: -999 Location Latitude Longitude Date localtime Sr/Ca Sr/Ca_SE Loblolly 18.7386 -64.3091 3/20/2013 1810 8.637 0.005 Loblolly 18.7386 -64.3091 3/20/2013 2100 8.646 0.004 Loblolly 18.7386 -64.3091 3/21/2013 100 8.640 0.014 Loblolly 18.7386 -64.3091 3/21/2013 400 8.621 0.011 Loblolly 18.7386 -64.3091 3/21/2013 600 8.649 0.015 Loblolly 18.7386 -64.3091 3/21/2013 900 8.636 0.009 Loblolly 18.7386 -64.3091 3/21/2013 1200 8.634 0.009 Loblolly 18.7386 -64.3091 3/21/2013 1500 8.636 0.012 Loblolly 18.7386 -64.3091 3/21/2013 1800 8.620 0.022 Punta Cana 18.8061 -68.5721 7/21/2017 400 8.930 0.006 Punta Cana 18.8061 -68.5721 7/21/2017 700 8.930 0.009 Punta Cana 18.8061 -68.5721 7/21/2017 1000 8.924 0.002 Punta Cana 18.8061 -68.5721 7/21/2017 1300 8.916 0.010 Punta Cana 18.8061 -68.5721 7/21/2017 1600 8.866 0.003 Punta Cana 18.8061 -68.5721 7/21/2017 1900 8.767 0.010 Punta Cana 18.8061 -68.5721 7/21/2017 2200 8.778 0.007 Punta Cana 18.8061 -68.5721 7/22/2017 300 8.841 0.007 KML 24.8265 -80.8145 8/3/2017 2100 8.747 0.005 KML 24.8265 -80.8145 8/4/2017 0 8.730 0.007 KML 24.8265 -80.8145 8/4/2017 300 8.748 0.005 KML 24.8265 -80.8145 8/4/2017 600 8.744 0.004 KML 24.8265 -80.8145 8/4/2017 900 8.749 0.005 KML 24.8265 -80.8145 8/4/2017 1200 8.745 0.008 KML 24.8265 -80.8145 8/4/2017 1500 8.735 0.004 KML 24.8265 -80.8145 8/4/2017 1800 8.747 0.004 KML 24.8265 -80.8145 8/4/2017 2100 8.748 0.007