Description: Age control and paleoceanographic evidence of marine sediment records might be challenged if authors solely build their stratigraphy on visual correlation to apparently well‐dated records from the same ocean basin, using, for example, highly resolved X‐ray fluorescence‐based element‐count records and correlation tools such as AnalySeries. While per se perfectly reasonable, this approach bears the risk of missing stratigraphic gaps in the sedimentary record and thus might result in imprecise and/or flawed interpretations. Here we present a unique series of 14 planktic 14C ages from a 7‐cm section of East Pacific Rise core PS75/059‐2. The ages suggest a 14‐ky‐long period of low‐to‐zero deposition during Last Glacial Maximum, mainly marked by continuous redistribution of winnowed foraminifers, probably the result of enhanced bottom currents, moreover, by some bioturbational mixing. On the basis of this data we demonstrate the impact of the hiatus on a South Pacific transect of apparent benthic ventilation ages (ΔΔ14C values) and their meaning for estimates of CO2 stored in Last Glacial Maximum Pacific deep waters.

Description: The unknown Zoophycos-producing organism potentially reworks marine sediments far deeper (up to〉1 m) than common bioturbational mixing of the topmost sediment layer. The Zoophycos producer displaces planktonic foraminifera tests down to deep sediment levels hence, may seriously bias the faunal and isotopic composition and in particular, the radiocarbon age (14C) of the ambient host sediment. Here we present three high-resolution 14C records from sediment cores retrieved at intermediate water depths off Brazil, New Zealand, and Norway where Zoophycos burrows have biased 14C ages by 1000–5000 years. Based on closely spaced 14C ages and 14C plateau tuning we distinguish particular episodes with enhanced Zoophycos production that coincide with time spans of decreased sedimentation and thus, with probably reduced benthic nutrition. Off New Zealand, the actual burrowing activity was dated close to the Bølling/Allerød–Younger Dryas boundary. Displaced grains are traced from the ancient sediment surface of the Younger Dryas as far back as to the onset of Heinrich Stadial 1 and the terminal Last Glacial Maximum. These displaced 14C ages and similar 14C records obtained from two other sediment cores suggest that Zoophycos producers generally mount a burrowing campaign during times when environmental conditions are switching toward a starved sedimentation regime. During these tipping points Zoophycos spreiten probably serve as storage space for nutrient-rich particles foraged at the sediment surface and bioturbational mixed layer.

Description: In three Holocene high-resolution sediment cores from the Nordic Seas, the Barents Sea continental margin and eastern Fram Strait, we established narrow-spaced 14C records of various planktic foraminifera species to reconstruct local variations in the reservoir age of surface and subsurface waters. In the two northern cores Neogloboquadrina pachyderma (sin.) (Nps) shows a distinct Early Holocene 14C plateau at 9.3 to 9.1 14C ka, that we tuned to an atmospheric 14C plateau near 9.0 to 8.7 14C ka (IntCal 2013) that extends from 10.2 to 9.6 calendar ka. The outlined difference in (average) 14C age suggests a reservoir age of ∼400 years for the subsurface dweller Nps. Different planktic foraminifers that inhabit different water masses document different reservoir ages. In contrast to Nps the near-surface dweller N. incompta reveals an average reservoir age of 150 years, however, a further near-surface dweller, Turborotalita quinqueloba, a local Early Holocene reservoir age of up to 720 years at the Barents Sea continental margin. The latter age may indicate a local admixture of old and less saline Arctic surface waters from the East Spitsbergen Current. The Early Holocene 14C plateau forms a robust basis for a better correlation of paleoceanographic signals in all three sediment cores. For example, the onset of a maximum in T. quinqueloba that marks the onset of the Early Holocene Thermal Maximum in the Arctic Gateway is now defined near 10.5 cal ka, an event that possibly reflects an enhanced advection of Atlantic surface waters up to the Arctic Ocean.

Description: Glacial-to-interglacial changes in atmospheric pCO2 are considered as largely controlled by processes in the Southern Ocean. In particular, upwelling both near coastlines and along the Polar Front is regarded as a major pathway of old CO2 from the deep ocean up to the sea surface and atmosphere, hence plays an important role in regulating the CO2 exchange between ocean and atmosphere. At the beginning of the last glacial termination, changes in ocean overturning circulation in the Southern Ocean probably triggered two huge events of CO2 outgassing from a deep-ocean reservoir into the atmosphere as revealed by Antarctic ice core records 1. They parallel two intervals of rapidly decreasing atmospheric 13C 2 and ∆14C 3. They probably concurred with two intervals of enhanced ocean upwelling, directly linking increased ventilation of the deep ocean to the deglacial rise in atmospheric CO2. To constrain the precise timing and origin of released CO2 we used paired records of marine 14C reservoir ages from the Pacific sector of the Southern Ocean, established by means of the 14C Plateau Tuning method 4. High surface ocean reservoir ages serve as tracer for upwelled old water masses. They were obtained from our centennial-scale resolution planktonic radiocarbon records of sediment cores off southern New Zealand and southern Chile. During the last peak glacial our 14C ages reveal planktonic reservoir ages of 1600 - 2200 yr exceeding previous estimates 5,6 by 400-1200 yr, but well agree to the previously reported high value of 1970 yr 7. Right at the onset of the last deglacial our records suggest an extreme drop down to a very low reservoir age of 200-400 yr matching the low estimates of 300-400 yr by 5,6,7,8. During terminal Heinrich-1 times, the values once more reached 1100 yr. This pattern of increased reservoir ages during peak glacial times (and the B/A) and strongly reduced values during the early deglacial parallels and precedes the 13C trends of atmospheric CO2 each and may have great implications for both constraining the history of past deep-water ages and related changes in the CO2 (1‰ 14C  -1.22 μmol DIC kg−1) 4 storage of South Pacific deep waters. (1) Marcott et al. 2014, Nature Vol. 514, 616 (2) Schmitt et al. 2013, Science Vol. 336, 711 (3) Bronk Ramsey et al. 2012, Science Vol. 338, 370 (4) Sarnthein et al. 2013, Clim. Past Vol. 9, 2595 (5) Pahnke et al. 2005, Science Vol. 307, 1741 (6) Ronge et al. 2016, Nature Comm. Vol. 7, 11487 (7) Sikes et al. 2000, Nature Vol. 405, 555 (8) Siani et al. 2013, Nature Comm. Vol. 4. 2758