Holocene sea subsurface and surface water masses in the Fram Strait – Comparisons of temperature and sea-ice reconstructions

Abstract

20Two high-resolution sediment cores from eastern Fram Strait have been investigated 21 for sea subsurface and surface temperature variability during the Holocene (the past ca 12,000 22 years). The transfer function developed by Husum and Hald (2012) has been applied to 23 sediment cores in order to reconstruct fluctuations of sea subsurface temperatures throughout 24 the period. Additional biomarker and foraminiferal proxy data are used to elucidate variability 25 between surface and subsurface water mass conditions, and to conclude on the Holocene 26 climate and oceanographic variability on the West Spitsbergen continental margin. Results 27 consistently reveal warm sea surface to subsurface temperatures of up to 6°C until ca 5 cal ka 28 BP, with maximum seawater temperatures around 10 cal ka BP, likely related to maximum 29 July insolation occurring at that time. Maximum Atlantic Water (AW) advection occurred at 30 surface and subsurface between 10.6 and 8.5 cal ka BP based on both foraminiferal and 31 dinocyst temperature reconstructions. Probably, a less-stratified, ice-free, nutrient-rich surface 32 ocean with strong Atlantic Water advection prevailed in the eastern Fram Strait between 10 33 and 9 cal ka BP. Weakened Atlantic Water contribution is found after ca 5 cal ka BP when 34 © 2015. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ subsurface temperatures strongly decrease with minimum values between ca 4 and 3 cal ka 35 BP. Cold conditions during that time are furthermore supported by high planktic foraminifer 36 shell fragmentation and  18 O values of the subpolar planktic foraminifer species T. 37 quinqueloba. While IP 25 -associated indices as well as dinocyst data suggest a sustained 38 cooling due to a decrease in early summer insolation and consequently sea-ice increase since 39 about 7 cal ka BP in surface waters, planktic foraminiferal data including stable isotopes 40 indicate a slight return of stronger subsurface Atlantic Water influx since ca 3 cal ka BP. The 41 observed decoupling of surface and subsurface waters during the later Holocene is most likely 42 attributed to a strong pycnocline layer separating cold sea-ice fed surface waters from 43 enhanced subsurface Atlantic Water advection. This may be related to changes in North 44 Atlantic subpolar versus subtropical gyre activity. 45 46 Husum, K., Hald, M., 2012. Arctic planktic foraminiferal assemblages: Implications for 47 subsurface temperature reconstructions. Marine Micropaleontology 96-97, 38-47. 48 49 world's oceans. Northward flowing warm and saline Atlantic Water via the eastern Fram 60 Strait strongly contributes to the Arctic Ocean's heat budget. 61 Reconstructions of past climate and oceanographic conditions are essential for 62 understanding and modelling of the current and future climate. Extending the record of ocean 63 temperatures beyond the era of instrumental measurements facilitates improved knowledge 64 about the long-term mechanisms of...

Local ice caps in Finderup Land, North Greenland, survived the Holocene Thermal Maximum

“…The early deglaciation of Finderup Land at~10.5 cal. ka BP as recorded in our proglacial lake records generally coincides with both increased surface air temperatures ) and subsurface ocean temperatures in Fram Strait (Werner et al 2016) (Fig. 7).…”

“…E. Peak subsurface temperatures based on planktic foraminiferal fauna assemblages ( SST 100) (Werner et al . ). [Colour figure can be viewed at www.boreas.dk]…”

“…D. Summer temperature (JJA) at 79°N (grey) with RCP 2.6 (light blue), 4.5 (blue) and 8.5 scenarios (dark blue) at 79°N). E. Peak subsurface temperatures based on planktic foraminiferal fauna assemblages (SST100)(Werner et al 2016). [Colour figure can be viewed at www.boreas.dk]…”

Atlantic Water advection vs. glacier dynamics in northern Spitsbergen since early deglaciation

“…Bauch et al, 2001;Carbonara et al, 2016;Groot et al, 2014;Müller and Stein, 2014;Rigual-Hernández et al, 2017;Risebrobakken et al, 2011;Telesiński et al, 2015;Werner et al, 2013Werner et al, , 2016, coinciding with a general warming trend in the entire Svalbard region -especially after the PBO (e.g. Hald et al, 2004;Rasmussen et al, 2012;Sarnthein et al, 2003;Skirbekk et al, 2010;Ślubowska et al, 2005; this study, see Fig.…”

Early Holocene Temperature Oscillations Exceed Amplitude of Observed and Projected Warming in Svalbard Lakes

“…As seen in Figure e, subsurface temperatures display a prominent peak around 10 ka BP that is unmatched in the remainder of the Holocene. Werner et al () infer a similar pattern of temperature change in the adjacent eastern Fram Strait. In addition, an IP 25 reconstruction from the same site suggests that the seasonal sea ice margin had retreated north of Svalbard at this time.…”