A decadal‐scale Holocene sea surface temperature record from the subpolar North Atlantic constructed using diatoms and statistics and its relation to other climate parameters

Abstract

A sediment core from Reykjanes Ridge has been studied at 10‐ to 50‐year time resolution to document variability of Holocene surface water conditions in the western North Atlantic and to evaluate effects of Holocene ice‐rafting episodes. Diatom assemblages are converted to quantitative sea surface temperatures (SST) using three different transfer functions. Spectral and scale‐space methods are also applied on the records to explore variability at different timescales. Diatom assemblage and SST records clearly show that decaying remnants of the Laurentide ice sheet strongly influenced early Holocene climate in the western North Atlantic. This overrode the predominance of Milankovitch forcing, which played a key role in the development of Holocene climate in the eastern North Atlantic and Nordic Seas. Superimposed on general Holocene climate change is high‐frequency SST variability on the order of 1°−3°C. The record also documents climatic oscillations with 600‐ to 1000‐, ∼1500‐, and 2500‐year periodicities, with a time‐dependent dominance of different periodicities through the Holocene; a clear change in variability occurred about 5 ka BP. The SST record also provides evidence for Holocene cooling events (HCE) that, in some cases, correlate to documented southward intrusions of ice into the North Atlantic.

Multicentennial Variability of the Sea Surface Temperature Gradient across the Subpolar North Atlantic over the Last 2.8 kyr*,+

“…Core Rapid 21-3K was sampled continuously at 1.0-cm intervals and analyzed at 1-to 5-cm intervals with a resolution of 8-10 yr for the interval AD 800-1770, representing the highest-resolution diatom SST reconstruction from the subpolar North Atlantic for this period, and 40 yr for interval 800 BC-AD 800. The composite core CR 948/ 2011 (Andersen et al 2004a;Berner et al 2011) from the Vøring Plateau (66858.189N, 07838.369W) consists of cores MD95-2011 (Birks and Koc x 2002;Berner et al 2011) and JM97-948/2A (Andersen et al 2004a). The age model for the core was based on AMS 14 C and 210 Pb dates.…”

“…The age model for the core was based on AMS 14 C and 210 Pb dates. Further details of the material and age model are given by Andersen et al (2004a) and Berner et al (2011).…”

“…Marine planktonic diatoms were used to reconstruct past aSST because they are proven to be good indicators of surface water conditions in the region (Koc x-Karpuz and Schrader 1990; Andersen et al 2004a;Berner et al 2008 Ruddiman and Glover (1975), Hansen and Østerhus (2000), and Orvik and Niiler (2002). siliceous-walled algae, which constitute the major part of the phytoplankton thus being major primary producers in oceans.…”

“…However, suborbitalscale variability has occurred throughout the Holocene, but the nature and the forcing mechanisms of this variability are not well constrained (Denton and Karlén 1973;Bond et al 1997;Bianchi and McCave 1999;deMenocal et al 2000;Berner et al 2008;Divine et al 2010). Historical records and proxy climate data from the Northern Hemisphere have provided evidence for the most recent major climate anomalies, like the warm Medieval warm period (MWP) between AD 800 and 1400 (e.g., Lamb 1965;Bradley et al 2003;Mann and Jones 2003;Berner et al 2011), and the following colder era, the Little Ice Age (LIA) between AD 1400 and 1900 (Grove 1988;Bradley and Jones 1993;Moberg et al 2005;Mann et al 2008).…”

“…The principal time scales of the variability and the most prominent warming/ cooling events of the late Holocene in the area were identified by spectral and scale-space methods. The results were then compared with the previously published aSST record from the Vøring Plateau in the Norwegian Sea (Andersen et al 2004a;Berner et al 2011). The variability of the aSST gradient between these two sites was analyzed and then placed in the context of possible past changes in the oceanic circulation.…”