Sea ice and millennial-scale climate variability in the Nordic seas 90 kyr ago to present

Abstract

In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial-scale climatic events (Dansgaard/Oeschger events) using the sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species in a record from the southeast Norwegian Sea. We demonstrate that expansion and retreat of sea ice varies consistently in pace with the rapid climate changes 90 kyr ago to present. Sea ice retreats abruptly at the start of warm interstadials, but spreads rapidly during cooling phases of the interstadials and becomes near perennial and perennial during cold stadials and Heinrich events, respectively. Low-salinity surface water and the sea ice edge spreads to the Greenland–Scotland Ridge, and during the largest Heinrich events, probably far into the Atlantic Ocean.

Reconstruction of hydrographic changes in the southern Norwegian Sea during the past 135 kyr and the impact of different foraminiferal Mg/Ca cleaning protocols

“…[] and Hoff et al . [], respectively. For the lower part of the core, ∼20 and 50 specimens of M. barleeanus (size fraction 150–315 µm) and N. pachyderma (size fraction 150–250 µm) were picked, respectively, for stable isotope analyses.…”

“… Correlation of magnetic susceptibility as well as planktic and benthic δ 18 O in JM‐FI‐19PC [ Ezat et al ., ; Hoff et al ., , this study] and δ 18 O values from Greenland Ice Core Project (NGRIP) on the Greenland Ice Core Chronology 2005 (GICC05) [ Seierstad et al ., ; Rasmussen et al ., , and references therein]. Solid black horizontal lines mark tephra layers identified in both marine and ice cores [ Davies et al ., ].…”

“…The d 18 O for the benthic foraminiferal species Melonis barleeanus for the upper 7 m and the planktic foraminiferal species N. pachyderma for the upper 8 m of the 11 m long core JM11-FI-19PC were published in Ezat et al [2014] and Hoff et al [2016], respectively. For the lower part of the core, 20 and 50 specimens of M. barleeanus (size fraction 150-315 mm) and N. pachyderma (size fraction 150-250 mm) were picked, respectively, for stable isotope analyses.…”

Regional seesaw between the North Atlantic and Nordic Seas during the last glacial abrupt climate events

“…Rasmussen and Thomsen, 2004;Dokken et al, 2013). In parallel, the few direct but qualitative sea-ice reconstructions based on lipid biomarker analyses (Müller and Stein, 2014;Hoff et al, 2016) yielded contrasting interpretations. Here, we provide direct and quantitative reconstructions of variations of seasurface conditions from a compilation of three Norwegian Sea cores and one northern Northeast Atlantic core strategically positioned across the Faeroe-Iceland Ridge to track rapid hydrographic changes (Dokken and Jansen, 1999;Eynaud et al, 2002;Rasmussen and Thomsen, 2004;Dokken et al, 2013) (Fig.…”

A spatio-temporal reconstruction of sea-surface temperatures in the North Atlantic during Dansgaard-Oeschger events 5–8

“…It is clear that the oceanic changes associated with the NAO are not large enough to explain the amplitude of the ocean variability during DO-events Second, the PSR from the HadCM3 model pool is the only reconstruction where the GS9 to GI8 temperature difference is visible much beyond the North Atlantic Ocean. Previous literature (Broecker, 2000;Gildor and Tziperman, 2003;MassonDelmotte et al, 2005;Li et al, 2005Li et al, , 2010Dokken et al, 2013;Hoff et al, 2016) suggests that changes in the sea-ice cover 25 amplify the temperature response on Greenland over the DO-transition. We suggest that the lack of sea-ice change in the HadCM3 nohose and CCSM4 model pool based PSRs is the primary reason for the weak temperature signal over Greenland in the surrogate reconstructions.…”