# 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-global.txt # Data_Download_Description: NOAA Template File; Global 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: Global Coral Ocean Sites # Location: Global Ocean # Northernmost_Latitude: 26.2999666666667 # Southernmost_Latitude: -5.50141666666667 # Easternmost_Longitude: 118.45695 # Westernmost_Longitude: -158.242266666667 # Elevation_m: #--------------------------------------- # Data_Collection # Collection_Name: Global Sr/Ca Kilbourne2025 # First_Year: 2013 # Last_Year: 2021 # 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) # ## StationID sample identification,,,,,instrumental,,,C, ## Latitude latitude,,,degree north,,instrumental,,,N,-90 to 90 for S to N ## Longitude longitude,,,degree east,,instrumental,,,N,-180 to 180 for W to E ## Samp_Depth collection water depth,,,meter,,instrumental,,,C,this is the depth in the water column at which the water sample is taken ## Date collection date,,,day of year,,instrumental,,,C, ## Sr/Ca strontium/calcium,sea water,,millimole per mole,,instrumental,,inductively-coupled plasma atomic emission spectroscopy,N,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 ## SST sea surface temperature,sea water,,degree Celsius,,instrumental,,,N,taken from shipboard instrumentation #------------------------ # Data: # Data lines follow (have no #) # Data line format - tab-delimited text, variable short name as header # Missing_Values: -9999 StationID Latitude Longitude Samp_Depth Date Sr/Ca Sr/Ca_SE SST Dewakang Kecil Island, East Java Sea -5.5014 118.45695 -9999 04/25/13 8.641 0.006 -9999 Dewakang Kecil Island, East Java Sea -5.5014 118.4563833 -9999 04/25/13 8.662 0.010 -9999 Doangdoangan Besar Island, East Java Sea -5.3824 117.91435 -9999 04/27/13 8.653 0.007 -9999 Kalukalukuang Island, East Java Sea -5.1784 117.6524667 -9999 04/28/13 8.643 0.005 -9999 Kalukalukuang Island seamount -9999 -9999 -9999 04/28/13 8.645 0.006 -9999 Marasende Island, East Java Sea -5.1183 118.1409333 -9999 04/29/13 8.633 0.007 -9999 Green Island, West Philippine Sea 22.6569 121.4721 10 06/02/13 8.644 0.006 -9999 Kusu Island, Singapore Strait 1.2257 103.8601167 -9999 09/12/14 8.644 0.005 -9999 Kusu Island, Singapore Strait 1.2257 103.8601167 -9999 10/15/14 8.647 0.005 -9999 Keawaula Beach, Oahu 21.5481 -158.2422667 1.2 10/18/17 8.657 0.009 -9999 Kaneohe Bay, Oahu 21.4865 -157.8293333 6.7 10/14/17 8.641 0.004 26.5 west side 13.1780 -59.64058333 -9999 03/25/19 8.672 0.001 -9999 north side 13.3094 -59.57881667 -9999 03/26/19 8.675 0.002 -9999 east side 13.1993 -59.4976 -9999 03/26/19 8.678 0.002 -9999 south side 13.1290 -59.42936667 -9999 03/26/19 8.671 0.002 -9999 BATS station 13.1780 -59.64058333 5 03/25/19 8.652 0.006 28.0 DF-W1 Deerfield Beach 26.3000 -80.06963333 3.5-5.5 10/06/21 8.623 0.008 27.8 PMP-W1 Pompano Beach, ~450 m offshore 26.2194 -80.08546667 3.5-5.5 10/05/21 8.630 0.004 27.2 PMP-W2 ~400 m offshore 26.2193 -80.0862 3.5-5.5 10/05/21 8.616 0.006 27.2 PMP-W3 ~250 m offshore 26.2197 -80.08736667 3.5-5.5 10/05/21 8.618 0.007 27.2 PMP-W4 nearshore 26.2200 -80.0889 3.5-5.5 10/05/21 8.627 0.004 27.8