Refining Globigerinoides ruber Mg/Ca paleothermometry in the Atlantic Ocean

Evaluating controls on planktonic foraminiferal geochemistry in the Eastern Tropical North Pacific

“…Consistent throughout all of these calibration studies is an exponential Mg/Ca ratio:temperature sensitivity of 8-10% change in ratio per • C (Anand et al, 2003;Bolton et al, 2011;Dekens et al, 2002;Lea et al, 1999;Martínez-Botí et al, 2011;Mashiotta et al, 1999;McConnell and Thunell, 2005;Regenberg et al, 2009). The influences of secondary factors such as salinity and carbonate chemistry are still being evaluated, and in many cases appear to be species -and/or regionspecific (Arbuszewski et al, 2010;Dekens et al, 2002;Evans et al, 2016;Hertzberg and Schmidt, 2013;Hönisch et al, 2013;Kısakürek et al, 2008;Russell et al, 2004).…”

“…Although results from some field-based studies have suggested a much larger influence (15-57% increase per salinity unit) of salinity on shell Mg/Ca (Arbuszewski et al, 2010;Ferguson et al, 2008), reexamination of study sites, samples, and/or methods has resulted in alternate explanations for elevated Mg/Ca ratios (Hönisch et al, 2013). These include variable calcite preservation within a single ocean basin (Hertzberg and Schmidt, 2013), and changes in seawater carbonate chemistry (van Raden et al, 2011).…”

Assessing the reliability of foraminiferal Mg/Ca thermometry by comparing field-samples and culture experiments: a review

“…Tak ing into ac count the find ings of Hertzberg and Schmidt (2013) for G. ruber Mg/Ca palaeothermometry, we use the av erage depth of 30 m for the d 18 O sw es ti ma tion since a num ber of stud ies have shown that the pre ferred depth hab i tat of G. ruber is ~0-30 m (e.g., Schmuker and Schiebel, 2002;Waelbroeck et al, 2005;Kuroyanagi et al, 2008;Numberger et al, 2009;Grauel and Bernasconi, 2010;Mortyn et al, 2011;Hönisch et al, 2013;Hertzberg and Schmidt, 2013;Antonarakou et al, 2015;Kontakiotis, 2016) and the ap pro pri ate cal i bra tion equa tions (Dekens et al, 2002) for the dis so lu tion cor rec tion de pend ing on the lo ca tion (Mg/Ca = 0.38 exp 0.09 [SST-0.61 (core depth km)] for the At lan tic and Mg/Ca = 0.38 exp 0.09 [SST-0.61 (core depth km)-1.6] for In dian and Pa cific oceans). The Dekens et al (2002) dis so lu tion cor rec tion was pre ferred in stead of that from Regenberg et al (2006) since the lat ter in cludes sam ples only from the Ca rib bean Sea, while the for mer in te grates over a wider area, in clud ing sam ples from the At lan tic and the Pa cific oceans.…”

“…Foraminiferal Mg/Ca ther mom e try is a rap idly de vel op ing and widely used tool for palaeoceanographic re con struc tion (e.g., Lea et al, 2000;Anand et al, 2003;Hoogakker et al, 2009;Kontakiotis et al, 2011;Martínez-Botí et al, 2011;Honisch et al, 2013;Hertzberg and Schmidt, 2013;Lea, 2014;Antonarakou et al, 2015;Spero et al, 2015). The geo chem is try of foraminiferal tests re flects the en vi ron men tal con di tions in which the foraminifera grew and there fore con trib ute in re con struct ing past ocean cli mate.…”

“…The ini tial mile stones, such as the first at tempt to de duce gla cial trop i cal SSTs us ing Mg/Ca (Hastings et al, 1998), the first cal i bra tions made on cul tured whole shells , or the first detailed sed i ment trap cal i bra tions (Anand et al, 2003;Martínez-Botí et al, 2011), was fol lowed by new ones fo cus ing mostly on its con fi dent use on tar geted key (morpho)spe cies (e.g., Globigerinoides ruber) on both short (mod ern or late Quater nary; Steinke et al, 2005;Thirumalai et al, 2014;Antonarakou et al, 2015) and lon ger time scales over the past 17 My (Wara et al, 2005; Me dina-Elizalde and Lea, 2005;Medina-Elizalde et al, 2008;Lear et al, 2015). Es pe cially for the mod ern ma te rial (core-tops, plank ton tows and sed i ment traps), in which the Mg/Ca sig nal is com pli cated by the com bined in fluence of en vi ron men tal pa ram e ters (e.g., sa lin ity, cal cite sat u ration state; Kisakürek et al, 2008;Hoogakker et al, 2009;Kontakiotis et al, 2011;van Raden et al, 2011;Hönisch et al, 2013;Hertzberg and Schmidt, 2013;Hertzberg et al, 2016) and/or bi o log i cal pro cesses (Hathorne et al, 2009;Wit et al, 2010;Bolton et al, 2011;Nehrke et al, 2013;Spero et al, 2015), prog ress has been rapid be cause of im prove ments in an a lyt i cal in stru men ta tion and meth ods (Haley and Klinkhammer, 2002;Benway et al, 2003;Klinkhammer et al, 2004;Rosenthal et al, 2004;Greaves et al, 2008;. More over, the prog ress has been made in elu ci dating the im pact of chang ing sea wa ter Mg/Ca ra tios on Mg/Ca palaeothermometry (Me dina-Elizalde et al, 2008;Hasiuk and Lohmann, 2010;Broecker and Yu, 2011;Ev ans and Müller, 2012;…”