Climate variability of the last ~2700 years in the Southern Adriatic Sea: Coccolithophore evidences

Abstract

New information on palaeoenvironmental conditions over the past ~2700 years in the Central Mediterranean Sea have been acquired through the high-resolution study of calcareous nannofossils preserved in the sediment core SW104-ND14Q recovered in the Southern Adriatic Sea (SAS) at 1013-m water depth. The surface water properties at this open SAS site are sensitive to atmospheric forcing (acting both at local and regional scale) and the North Ionian Sea driven inflowing waters. Our data show a relationship between reworked coccolith abundances, flood frequency across the Southern Alps and the North Atlantic Oscillation (NAO) confirming their value as indicator of runoff/precipitation. Changes in the abundance of the opportunistic (r-strategist) species Emiliania huxleyi and deep dweller taxa Florisphaera profunda were used to reconstruct the upper water column stratification and associated changes in coccolithophorid productivity. The negative correlation between reworked coccoliths and the N-Ratio ( r = −0.44; p = 6−7) suggest that fresh water induced stratification is a controlling factor of the SAS coccolithophorid production. High coccolithophorid productivity levels occurred during dry periods and/or time intervals of inflowing salty and nutrient-rich Levantine Intermediate Waters favouring convection while lower levels took place during high freshwater discharge, mainly during the ‘Little Ice Age’ and two centennial scale intervals of weakest NAO around 200 BCE and 500 CE.

Solar forcing for nutricline depth variability inferred by coccoliths in the pre-industrial northwestern Mediterranean

“…Coccoliths are employed in a large set of paleoenvironmental and paleoceanographic reconstructions (Baumann et al, 2005) and in the Mediterranean Sea show a ready response to abrupt climate changes, such as Dansgaard-Oeschger events or Holocene rapid climatic changes, mainly in terms of primary productivity variability and vertical water column dynamics (Ausín et al, 2015;Bazzicalupo et al, 2018Bazzicalupo et al, , 2020Cascella et al, 2021;Colmenero-Hidalgo et al, 2004;Di Stefano et al, 2015;Flores et al, 1997;Incarbona et al, 2008Incarbona et al, , 2013Incarbona et al, , 2019aTriantaphyllou, 2014;Triantaphyllou et al, 2009a). More subtle seems to be the response to historical climate changes, generally lacking any sign of significant abundance variation or expressed like just general trends (Bonomo et al, 2016;Cascella et al, 2019;Vallefuoco et al, 2012), though primary productivity changes have been inferred during the Little Ice Age (Incarbona et al, 2010a) and, most importantly, for the first time, across the Industrial age (Pallacks et al, 2021). The shortage of robust evidence of coccolithophore changes contrasts with more evident variability found in planktonic foraminiferal assemblages (Incarbona et al, 2019b;Lirer et al, 2014;Margaritelli et al, 2016Margaritelli et al, , 2018Margaritelli et al, 2020b;Pallacks et al, 2021;Vallefuoco et al, 2012).…”

Climate evolution in the Adriatic Sea across the last deglaciation: A multiproxy approach combining biomarkers and calcareous plankton

“…The sediment core ND14Q-AR2 used for this study was retrieved from the deepest part of the South Adriatic basin. This area provides an ideal location for high resolution paleoclimatic reconstructions because of thick deglaciation and Holocene sedimentary sequences and recurrent tephra layers for geochronological constraints (Siani et al, 2004(Siani et al, , 2013Lowe et al, 2007;Jalali et al, 2018;Cascella et al, 2019;Totaro et al, 2022). Terrestrial and marine biomarkers were used to infer environmental changes such as Sea Surface Temperatures (SSTs), in tandem with terrestrial input associated with humidity changes on adjacent lands (Jalali et al, 2018;Ternois et al, 2000).…”

“…On the other hand, detailed calcareous plankton description from SAS are either scarce or mostly focused on planktonic foraminifera across the latest part of the deglaciation (Younger Dryas) to Holocene interval (Asioli et al, 1999(Asioli et al, , 2001Capotondi et al, 1999;Sangiorgi et al, 2003;Favaretto et al, 2008;Piva et al, 2008;Narciso et al, 2012;Siani et al, 2013). In the same interval very few data exist on the coccolithophore assemblages (Giunta et al, 2003;Sangiorgi et al, 2003;Narciso et al, 2012;Cascella et al, 2019) and do not focus on the detail changes that occurred during the deglaciation. The study of core ND14Q-AR2 provides the first paleoenvironmental reconstruction of the deglaciation in the SAS that comprehends coccolith, planktonic foraminifera and biomarker analysis at high-temporal resolution to explore multidecadal changes at a regional scale during the deglaciation.…”