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A composite North Atlantic record from DSDP Site 609 and IODP Site U1308 spans the past 300,000 years and shows that variability within the penultimate glaciation differed substantially from that of the surrounding two glaciations. Hematite stained grains exhibit similar repetitive down-core variations within the Marine Isotope Stage (MIS) 8 and 4-2 intervals, but little cyclic variability within the MIS 6 section. There is also no petrologic evidence, in terms of detrital carbonate-rich (Heinrich) layers, for surging of the Laurentide Ice Sheet through the Hudson Strait during MIS 6. Rather, very high background concentration of ice-rafted debris (IRD) indicates near continuous glacial meltwater input that likely increased thermohaline disruption sensitivity to relatively weak forcing events, such as expanded sea ice over deepwater formation sites. Altered (sub)tropical precipitation patterns and Antarctic warming during high orbital precession and low 65° N summer insolation appears related to high abundance of Icelandic glass shards and southward sea ice expansion. Differing European and North American ice sheet configurations, perhaps aided by larger variations in eccentricity leading to cooler summers, may have contributed to the relative stability of the Laurentide Ice Sheet in the Hudson Strait region during MIS 6. Supplement to: Obrochta, Stephen P; Crowley, Thomas J; Channell, James E T; Hodell, David A; Baker, Paul A; Seki, Arisa; Yokoyama, Yusuke (2014): Climate variability and ice-sheet dynamics during the last three glaciations. Earth and Planetary Science Letters, 406, 198-212 For data in MIS4-2 of DSDP Site 94-609 see Obrochta et al. (2012).

Mesopelagic organisms play a critical role in marine ecosystems, channelling energy and organic matter across food webs and serving as the primary prey for many open-ocean predators. Nevertheless, trophic pathways involving mesopelagic organisms are poorly understood and their contribution to food web structure remains difficult to assess (St. John et al., 2016). Existing data to assess mesopelagic feeding interactions and energy transfer are scattered in the literature or remain unpublished, making it difficult to locate and use such datasets. As part of the EU funded project SUMMER - Sustainable Management of Mesopelagic Resources H2020-BG-2018-2, GA: 817806) (https://summerh2020.eu/), we created MesopTroph, a georeferenced database of diet, trophic biogeochemical markers, and energy content of mesopelagic organisms and other marine taxa from the Northeast Atlantic and Mediterranean Sea, compiled from 191 published and non-published sources. MesopTroph includes seven datasets: (i) diet compositions from stomach content analysis, (ii) stable isotopes of carbon and nitrogen (δ13C and δ15N), (iii) fatty acid trophic markers (FATM), (iv) major and trace elements, (v) energy density, (vi) estimates of diet proportions, and (vii) trophic positions. The database contains information from 4918 samples, representing 51119 specimens from 499 species or genera, covering a wide range of trophic guilds and taxonomic groups. Metadata provided for each record include the location, dates and method of sample collection, taxonomic ranks (phylum, class, order, family), number and size (or size range) of sampled organisms, method/model used in data analysis, reference and DOI of the original data source. Compiled data were checked for errors, missing information, and to avoid duplicate entries, and scientific names and taxonomy were standardized.

Abrupt climate changes in the past have been attributed to variations in Atlantic Meridional Overturning Circulation (AMOC) strength. However, the exact timing and magnitude of past AMOC shifts remain elusive, which continues to limit our understanding of the driving mechanisms of such climate variability. Here we show a remarkably consistent signal of the 231Pa/230Th proxy that reveals a spatially coherent picture of western Atlantic circulation changes over the last deglaciation, during abrupt millennial-scale climate transitions. At the onset of deglaciation, we observe an early slowdown of circulation in the western Atlantic from around 19 to 16.5 thousand years ago (ka), consistent with the timing of accelerated Eurasian ice melting. The subsequent weakened AMOC state persists for over a millennium (~16.5-15 ka), during which time there is substantial ice rafting from the Laurentide ice sheet. This timing indicates a role for melting ice in driving a two-step AMOC slowdown, with a positive feedback sustaining continued iceberg calving and climate change during Heinrich Stadial 1. Supplement to: Ng, Hong Chin; Robinson, Laura F; McManus, Jerry F; Mohamed, Kais J; Jacobel, Allison W; Ivanovic, Ruza F; Gregoire, Lauren J; Chen, Tianyu (2018): Coherent deglacial changes in western Atlantic Ocean circulation. Nature Communications, 9(1)

The data originates from the gravity core MSM12/2-5-1 (57.538500, -48.738700, recovery 1494 cm, 3492 m water depth) taken during R/V Maria S. Merian cruise MSM12/2 in 2009 in the eastern Labrador Sea (Eirik Drift). The data should provide more precise information on the timing and duration of freshwater forcing, which may help to improve simulations for past and future changes in ocean circulation and climate. We have investigated the very well-dated and high-resolution sediment core from the Eirik Drift, representing an interval from the last deglaciation to Holocene, i.e., the last 19 ka. Four meltwater-related cold events have been identified by abrupt changes in sea surface characteristics, which are based on independent multiple biomarker proxies, including sea-ice proxy IP25 and phytoplankton biomarker IP25 index (PIP25) for sea ice cover, the alkenone unsaturation index for sea surface temperature (SST), and the percentage of tetra-unsaturated alkenones (%C37:4) for meltwater inflow, and X-ray fluorescence (XRF) scanning data. Furthermore, sortable silt mean size has been used to reflect changes in bottom current intensity. In conclusion, our study could improve our understanding of the impact of meltwater injection into subpolar regions on abrupt climate changes during the last glacial termination. Furthermore, the data support modelling results that higher frequency and amplitude of abrupt changes may occur during the transition states from background climates. We found that meltwater pulses following collapse of the Laurentide Ice Sheet and/or Greenland Ice Sheet might have triggered millennial-scale abrupt changes in surface freshening and sea ice concentrations in the Labrador Sea, as well as cooling atmospheric temperatures.

Iceberg calving has been assumed to be the dominant cause of mass loss for the Antarctic ice sheet, with previous estimates of the calving flux exceeding 2,000 gigatonnes per year. More recently, the importance of melting by the ocean has been demonstrated close to the grounding line and near the calving front. So far, however, no study has reliably quantified the calving flux and the basal mass balance (the balance between accretion and ablation at the ice-sheet base) for the whole of Antarctica. The distribution of fresh water in the Southern Ocean and its partitioning between the liquid and solid phases is therefore poorly constrained. Here we estimate the mass balance components for all ice shelves in Antarctica, using satellite measurements of calving flux and grounding-line flux, modelled ice-shelf snow accumulation rates and a regional scaling that accounts for unsurveyed areas. We obtain a total calving flux of 1,321 ± 144 gigatonnes per year and a total basal mass balance of -1,454 ± 174 gigatonnes per year. This means that about half of the ice-sheet surface mass gain is lost through oceanic erosion before reaching the ice front, and the calving flux is about 34 per cent less than previous estimates derived from iceberg tracking. In addition, the fraction of mass loss due to basal processes varies from about 10 to 90 per cent between ice shelves. We find a significant positive correlation between basal mass loss and surface elevation change for ice shelves experiencing surface lowering and enhanced discharge. We suggest that basal mass loss is a valuable metric for predicting future ice-shelf vulnerability to oceanic forcing. Supplement to: Depoorter, Mathieu A; Bamber, Jonathan L; Griggs, Jennifer; Lenaerts, Jan T M; Ligtenberg, Stefan R M; van den Broeke, Michiel R; Moholdt, Geir (2013): Calving fluxes and basal melt rates of Antarctic ice shelves. Nature, 502, 89-92

This study developed a unified taxonomic classification system for recent epifaunal benthic foraminifera species collected from surface sediment samples along the Southeast Pacific margin, including Cibicidoides wuellerstorfi, C. lobatulus, C. cf. ungerianus, Planulina ariminensis, P. ornata, and P. limbata. Morphological characteristics of these epifaunal benthic foraminifera specimens, such as test shape, periphery, chamber inflation, elongation, suture curvature, and wall porosity, were measured between December 2022 and June 2023. Furthermore, variations in morphological features like planoconvex tests, proloculus size, suture curvature, and pore patterns were observed among these foraminifera. The surface sediment samples were collected off the coasts of Chile and Peru between 1962 and 2014, covering latitudes from 12.70°S to 44.09°S and water depths ranging from 24 to 3,267 m. The temporal coverage of the samples spans the Holocene, with a focus on the late Holocene and modern samples. These samples were collected using various gear devices, including a multicorer (Sonne 156, Sonne 211, Meteor 92), a box corer (BIAC072014), a Petersen grab (USNS Eltanin), and a gravity core (Sonne 161). Detailed morphological examinations of the specimens were conducted using TM4000Plus HITACHI SEM imaging and a Leica S8 APO stereomicroscope, complemented by manual illustrations. The unified taxonomic criteria will enhance the accuracy of foraminifera-based proxies, such as stable isotopes and morphological studies, which are vital for paleoceanographic reconstructions.

Pelagic sediments from the subtropical South Atlantic Ocean contain geographically extensive Oligocene ooze and chalk layers that consist almost entirely of the calcareous nannofossil Braarudosphaera. Poor recovery and the lack of precise dating of these horizons in previous studies has limited our understanding of the exact number of acmes, their timing and durations, and the causes of their recurrence. Here we present a high-resolution, astronomically tuned stratigraphy of Braarudosphaera oozes (29.5-27.9 Ma) from Ocean Drilling Program Site 1264 in the subtropical southeastern Atlantic Ocean. We identify seven acme events in the Braarudosphaera abundance record. The longest lasting acme event corresponds to a strong minimum in the ~2.4-My eccentricity cycle, and four acme events coincide with ~110-ky and 405-ky eccentricity maxima. We propose that eccentricity-modulated precession forcing of the freshwater budget of the South Atlantic Ocean resulted in the episodic formation of a shallow pycnocline and hyperstratification of the upper water column. We speculate that stratified surface water conditions may have served as a virtual sea floor, which facilitated the widespread Braarudosphaera acmes. This explanation reconciles the contrasting distribution patterns of Braarudosphaera in the modern ocean, limited largely to shallow water coastal settings, compared to their relatively brief and expanded oceanic distribution in the past. Supplement to: Liebrand, Diederik; Raffi, Isabella; Fraguas, Ángela; Laxenaire, Rémi; Bosmans, Joyce H C; Hilgen, Frederik J; Wilson, Paul A; Batenburg, Sietske J; Beddow, Helen M; Bohaty, Steven M; Bown, Paul R; Crocker, Anya J; Huck, Claire E; Lourens, Lucas Joost; Sabia, Luciana (2018): Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean. Paleoceanography and Paleoclimatology, 33(5), 511-529

The Western Equatorial Pacific (WEP) warm pool, with surface temperatures >28 °C and a relatively deep thermocline, is an important source of latent and sensible heat for the global climate system. Because the tropics are not sensitive to ice‐albedo feedbacks, the WEP's response to radiative forcing can be used to constrain a minimum estimate of Earth system sensitivity. Climate modeling of pCO2‐radiative warming projections shows little change in WEP variability; here we use temperature distributions of individual surface and subsurface dwelling fossil foraminifera to evaluate past variability and possible radiative and dynamic climate forcing over the Plio‐Pleistocene. We investigate WEP warm pool variability within paired glacial‐interglacial (G‐IG) intervals for four times: the Holocene‐Last Glacial Maximum, ~2 Ma, ~3 Ma, and ~ 4 Ma. Our results show that these surface and subsurface temperature distributions are similar for all G‐IG pairs, indicating no change in variability, even as pCO2‐radiative forcing and other boundary conditions changed on G‐IG timescales. Plio‐Pleistocene SST distributions are similar to those from the Holocene, indicating WEP SSTs respond to pCO2‐radiative forcing and associated feedbacks. In contrast, Plio‐Pleistocene subsurface temperature distributions suggest subsurface temperatures respond to changes in thermocline temperature and depth. We estimate tropical temperature sensitivity for the mid‐Pliocene (~3 Ma) using our individual foraminifera SST dataset and a previously published high‐resolution boron isotope based pCO2 reconstruction. We find tropical temperature sensitivity was equal to, or less than that of the Late Pleistocene. Supplement to: Ford, Heather L; Ravelo, Ana Christina (2019): Estimates of Pliocene Tropical Pacific Temperature Sensitivity to Radiative Greenhouse Gas Forcing. Paleoceanography and Paleoclimatology, 34(1), 2-15