Strengthening Atlantic Inflow Across the Mid‐Pleistocene Transition. Issue 4 (27th April 2021)

• Record Type: Journal Article
• Authors: Barker, Stephen; Zhang, Xu; Jonkers, Lukas; Lordsmith, Sian; Conn, Stephen; Knorr, Gregor
• Is Part Of: Paleoceanography and paleoclimatology. Volume 36:Issue 4(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-04-27
• Subjects: Atlantic inflow -- mid‐Pleistocene transition -- nordic heat pump; Paleoceanography -- Periodicals; Paleoclimatology -- Periodicals; 551.46
• DOI: 10.1029/2020PA004200
• Languages: English
• ISSNs: 2572-4517

Abstract

Abstract: The development of larger and longer lasting northern hemisphere ice sheets during the mid‐Pleistocene Transition (MPT) coincided with global cooling. Here, we show that surface waters of the north‐eastern Atlantic actually warmed across this interval (∼1.2–0.8 Ma), which we argue reflects an increase in the north‐eastward transport of heat and moisture via the North Atlantic Current (NAC) into the Nordic Seas (the Atlantic Inflow). We suggest that simultaneous cooling and warming along the north‐western and south‐eastern margins (respectively) of the NAC during Marine Isotope Stage 28 (∼995 ka) reflected the increasing persistence of northern ice sheets as Atlantic Inflow increased. This resulted in a diachronous shift from ∼40 to ∼100 kyr cyclicity across the North East (NE) Atlantic as the growing influence of northern ice sheets spread southwards; to the north‐west of the NAC the first "100 kyr" cycle preceded Termination 12 (∼960 ka), while on the south‐eastern margin of the NAC the transition occurred ∼100 kyr later. Exploratory climate model simulations suggest that increasing Atlantic Inflow at this time could have accelerated ice sheet growth because pre‐existing moderately sized ice sheets allowed the positive effect of increasing precipitation to outpace melting. In addition, we propose that the dependence of post‐MPT ice sheets on moisture transport via the Atlantic Inflow may ultimately contribute to their apparent vulnerability to insolation forcing once a critical size threshold is crossed and high latitude ice sheets become starved of a vital moisture source. Key Points: Warming of interglacial surface northeast Atlantic across the mid‐Pleistocene Transition First "100 kyr" glacial cycle preceded Marine Isotope Stage 25 (∼0.95 Ma) Increasing Atlantic Inflow could promote ice sheet growth given pre‐existence of moderately sized ice sheets