Expedition 374 summary

Controls Since the mid‐Pleistocene Transition on Sedimentation and Primary Productivity Downslope of Totten Glacier, East Antarctica

“…The lithostratigraphic, physical, and diatom abundance observations, inferred to represent interglacial phases, are verified by the foundational body of work developed by multiple ocean drilling legs on sediments from similar time intervals and depositional environments in different sectors of the Antarctic margin. This includes Site 1095 from the Pacfic West Antarctic Peninsula sediment drift system (Barker & Camerlenghi, 2002; Barker et al, 1999), Site 1167 from Prydz Bay trough mouth fan (O'Brien et al, 2001; Passchier et al, 2003), Site U1361 from Wilkes Land continental rise (Escutia et al, 2011), and most recently from Sites U1523 and U1524 from the outer continental shelf and lower slope and the Ross Sea (McKay et al, 2019). The common conclusion drawn from this work being is that the characteristics observed in these intervals represent a shift to more ice‐distal conditions and sedimentation controlled by hemipelagic deposition under seasonal sea ice conditions.…”

“…Kim et al (2020) proposed that along‐slope transport associated with the ASC strengthened during past glacial periods as evidenced by enhanced winnowing of fine grained material in glacial sediments on the Iselin Bank in the Ross Sea sector. The higher clay content during glacials appears to go against this conclusion; however, direct grain size comparison between the records is difficult due to different methods and more importantly different depth environments with the shallower cores in Kim et al (2020) likely to be more significantly influenced by the ASC (McKay et al, 2019). Despite these differences in depositional environment between locations, both A005‐PC01 and C012‐PC05 exhibit very similar patterns of terrigenous input—high during glacials and low during interglacials (Figure 8).…”

“…All 14 C ages were calibrated into calendar ages using the online CALIB 7.1 software (Stuiver et al, 2020) and the Marine20 calibration curve (Heaton et al, 2020). Last appearance datums (LAD) of biostratigraphic indicators Rouxia leventerae (last occurrence at MIS 5/6 boundary) and Hemidiscus karstenii (last occurrence at MIS 6/7 boundary) were used as additional age constraints when constructing the age model (Bohaty et al, 1998;McKay et al, 2019;Zielinski & Gersonde, 2002) (supporting information Figures S1 and S2).…”

Expedition 377 Scientific Prospectus: Arctic Ocean Paleoceanography (ArcOP)

“…A major element in the global climate evolution during Cenozoic times was the transformation from warm Paleogene oceans with low latitudinal and bathymetric thermal gradients to the more recent modes of circulation characterized by strong thermal gradients, oceanic fronts, cold deep oceans, and cold high-latitude surface waters (e.g., Miller et al, 1987;Zachos et al, 2001Zachos et al, , 2008McKay et al, 2019). Throughout the Cenozoic, the climate on Earth changed from one extreme (Paleogene Greenhouse lacking major ice sheets) to another (Neogene Icehouse with bipolar glaciation).…”

“…CO 2 concentrations of up to around 2000 ppm have been estimated for the late Paleocene and earliest Eocene periods (Figure F1) (Pearson and Palmer, 2000;Pagani et al, 2005;Lowenstein and Demicco, 2006;Royer, 2006;Zachos et al, 2008;Kent and Muttoni, 2013;Masson-Delmotte et al, 2013). Bottom temperatures in the early Eocene, the time of maximum Cenozoic warmth that peaked at the Paleocene/Eocene Thermal Maximum (about 55.8 Ma) and the Early Eocene Climatic Optimum (about 52-50 Ma), were of the order of 12°-14°C, and large-scale continental ice sheets were probably absent (Figure F1) (Miller et al, 1987;Lear et al, 2000;Pearson and Palmer, 2000;Zachos et al, 2008;Expedition 318 Scientists, 2010;McKay et al, 2019). The climate in lowland settings along the Wilkes Land coast of Antarctica, for example, supported the growth of highly diverse, near-tropical forests characterized by mesothermal to megathermal floral elements (Pross et al, 2012).…”