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Abstract. Biostratigraphy is frequently used to generate age models and is significant to understanding the rate and timing of Cenozoic climate change. Records from the Southern Ocean (SO) are particularly valuable in understanding the past behavior of the Antarctic Ice Sheet, whereby clues to this behavior can be gained from the presence and composition of preserved microfossils. Diatoms, a nearly ubiquitous group of microalgae that make cell walls out of opal, preserve well in Southern Ocean sediments and have been used extensively in Southern Ocean biostratigraphy. Here, we present an updated diatom biostratigraphy of the Southern Ocean extending 3.3 Myr from sediments recovered during International Ocean Discovery Program (IODP) Expedition 382 “Iceberg Alley” Site U1537. Furthermore, we compare a tuned age model to a paleomagnetic-based age model to provide two independent estimates of ages of these datums with quantified uncertainty. The high sedimentation rate found at Site U1537 allows detailed age assessment, allowing the generation of more finely tuned age models in Southern Ocean sediments. 

We combine geomorphological and sediment core evidence to investigate phases of ice margin stability and instability during retreat of the Boothia Lancaster Ice Stream (BLIS) of the NE Laurentide Ice Sheet (LIS) since the Last Glacial Maximum (LGM). Sediment cores 2008029-059 PC and TWC (59CC) and 2013029-064 PC (64 PC) from Lancaster Sound and Baffin Bay, respectively, represent LGM through Holocene environments, including three Baffin Bay Detrital Carbonate (BBDC) events that have been thought to manifest calving events within Lancaster Sound. Previous mapping of glacigenic landforms shows that 64 PC lies within the LGM limit of the convergent BLIS and Tasiujaq Ice Stream (TIS) on the northeastern Baffin Island shelf, while 59CC terminates within subglacial/ice marginal sediments termed the Baffin Shelf Drift (BSD), capturing the history of BLIS retreat from 15.3 cal ka BP onward. In 64 PC, a basal sediment gravity flow deposit is overlain by dolomite-rich BBDC 2, which is re-interpreted here as a subglacial/ice marginal deposit and renamed GZ-BBDC. Both gravity flows are interpreted to have formed during retreat of the confluent TIS and BLIS from the LGM maximum extent. Overlying GZ-BBDC, in 64 PC, is a finely laminated lithofacies interpreted as an ice-shelf facies formed beneath the ice shelf fronting the confluent TIS and BLIS when it occupied a large LGM grounding zone wedge (GZW) in northern Baffin Bay. The ice-shelf facies indicates temporary stabilization of the conjoined TIS and BLIS. The overlying thin black glaciomarine diamicton records disintegration of the ice shelf and retreat of the TIS. Ice retreat over Cretaceous and younger bedrock into Lancaster Sound is recorded by dark brown diamicton and glaciomarine sediments in 59CC. The overlying tan, detrital carbonate-rich glaciomarine diamicton, BBDC 1 in 59 PC, manifests calving retreat of the BLIS onto the Paleozoic carbonate bedrock within Lancaster Sound by 15 cal ka BP. A slightly later onset of BBDC 1 in 64 PC, of ca.14.5 cal ka BP, points to the influence of local conditions such as sea ice and local iceberg calving on the distribution of IRD off of Pond Inlet. The pause in ice rafting and detrital carbonate deposition between BBDC 1 and BBDC 0 within the Younger Dryas chron likely results from BLIS readvance to Devon Island and its stabilization there until 11.6 cal ka BP. BLIS retreat into Prince Regent Inlet marks the onset of BBDC 0. These new results indicate multiple periods of instability of the BLIS, which are responsible for BBDC events identified throughout Baffin Bay. 

Computed Tomography (CT) Data Collected on IODP Site U1537 u-channel samples using the Oregon State University College of Veterinary Medicine Toshiba Aquillon 64 Slice Medical CT Scanner in collaboration with the Oregon State University Marine and Geology Repository.  U-channels were measured in batches of 8 with derived CT data selecting only a portion of these original files for each u-channel.  All data are archived in DICOM format and have been processed using SedCT Matlab Tools (Reilly et al., 2017; 10.1002/2017GC006884).   Files Include: U1537 U-Channel CT DICOM Files (Original).zip Data in DICOM format from original scans measured in batches of 8.  Includes excel spreadsheet with identifying information for which sections were measured in each scan. U1537A U-Channel CT DICOM Files (Split).zip Data in DICOM format, segmented so each u-channel is a sperate file.  Folder system organized by section with two subfolders included for scans that needed to be run in two scans (nominally sections longer than 1 m).  Includes U1537A sections: 24H-2A, 24H-3A, 24H-4A, 25H-3A, 25H-4A, 25H-5A, 25H-6A, 26H-2A, 26H-3A, 26H-4A, 26H-5A, 26H-6A, 26H-7A, 26H-8A, 27F-3A, 2F-4A. U1537D U-Channel CT DICOM Files (Split).zip Data in DICOM format, segmented so each u-channel is a sperate file.  Folder system organized by section with two subfolders included for scans that needed to be run in two scans (nominally sections longer than 1 m).  Includes U1537D sections: 24H-1W, 24H-2W, 24H-3W, 24H-4W, 24H-5W, 24H-6W, 25H-1W, 25H-2W, 25H-3W, 25H-4W, 25H-5W, 25H-6W, 25H-7W, 26H-5W, 26H-6W, 26H-7W, 27H-2W, 27H-3W, 27H-4W, 27H-5W,  27H-6W, 27H-W, 28F-1W, 28F-2W, 28F-3W, 29F-1W, 29F-2W, 29F-3W, 29F-4W, 30F-1W, 30F-2W, 30F-3W, 30F-4W, 31F-1W, 31F-2W, 31F-3W, 31F-4W. U1537A SedCT Output.zip CT#s, unscaled TIFF files, and PNG files scaled to 200-1400 HU for U1537A u-channels generated using SedCT Matlab Tools. U1537D SedCT Output.zip CT#s, unscaled TIFF files, and PNG files scaled to 200-1400 HU for U1537D u-channels generated using SedCT Matlab Tools. CTnumbers.zip CT# data organized for each core into excel spreadsheets. 

Abstract Over the last 3.3 million years, the Antarctic Ice Sheet (AIS) has undergone phases of ice sheet growth and decay, impacting sea level and climate globally. Presently, the largely marine‐terminating AIS loses mass primarily by iceberg calving and basal melt of ice shelves. Quantifying past rates and timing of AIS melt is vital to understanding future cryosphere and sea level changes. One proxy for past ice sheet instabilities is iceberg rafted debris (IRD) fluxes. However, traditional methods of IRD quantification are labor‐intensive. Here, we present a new method of identifying IRD grains in sediment core X‐ray images using a convolutional neural network machine learning algorithm. We present a 3.3‐million‐year record of AIS IRD melt events using sediment cores from International Ocean Discovery Program Sites U1536, U1537, and U1538 in the Southern Ocean's “Iceberg Alley.” We identify two increases in the IRD fluxes throughout this period, at ∼1.8 and 0.43 Ma. We propose that after 1.8 Ma, the AIS expanded and transitioned from a primarily terrestrial‐terminating to a primarily marine‐terminating ice sheet. Therefore, after 1.8 Ma, glacial terminations and AIS iceberg discharge are associated with variations in global ice volume, presumably through the mechanism of sea level and, therefore, grounding line change. The second AIS regime change occurs during the Mid‐Brunhes Event (∼0.43 Ma). After this time, there are heightened and continuous IRD fluxes at each glacial termination, indicating increased AIS size and instability after this time. 

{"Abstract":["Supplementary tables in support of "Antarctic response to orbital forcing during the intensification of extensive bipolar glaciation (1.75-3.30 Ma) from relative paleomagnetic intensity (RPI) stratigraphy of the Dove Basin, Scotia Sea, in Iceberg Alley.""]} 

Data files for rock magnetic data collected on discrete samples at the Institute for Rock Magnetism, University of Minnesota on a Quantum Designs Magnetic Properties System 3 (MPMS3) and Lakeshore Model 8600 Vibrating Sample Magnetometer (VSM). Data include Field Cooled (FC), Zero Field Cooled (ZFC), and Low Temperature Cycling of Room Temperature Saturation Isothermal Remanent Magnetization (LTC-RTSIRM) curves measured on the MPMS and Hysteresis Loops, Direct Current Demagnetization Curves, and Hysteresis Loops collected on the VSM. 

The Table S1-S6 are curated breakout notes from the NSF-funded FUTURE 2024 Workshop (March 26-28, 2024).  During the workshop, the first day of discussions focused on “Critical science questions that require seafloor sampling,” where participants: (I) defined the important sample types/sampling environment of their research; (II) assessed how well this seafloor environment is currently sampled; (III) reviewed how sample repositories/databases are currently used; and, (IV) evaluated justifications for acquiring new samples. Each breakout session culminated with a discussion of (V) what important science questions could be addressed soon (5–10 years), with existing or forthcoming assets and technologies, versus (VI) what might take longer (10+ years) and/or require the development of new assets or technologies. These motivating topics fed into the second day of discussions, which focused on “Aligning seafloor sampling technology with critical science questions.” Groups were guided by a common set of prompts, including what current resources were essential to the participants’ research, and what were the greatest challenges they faced in recovering the materials needed. The participants also discussed whether they could acquire the materials needed to address their science questions given current US assets (Figure 1 in FUTURE 2024 PI-team, 2024, AGU Advances 2024AV001560), how sample repositories and databases could be optimized for science needs, and the justification for acquiring or developing new technologies. 

The Table S1-S6 are curated breakout notes from the NSF-funded FUTURE 2024 Workshop (March 26-28, 2024).  During the workshop, the first day of discussions focused on “Critical science questions that require seafloor sampling,” where participants: (I) defined the important sample types/sampling environment of their research; (II) assessed how well this seafloor environment is currently sampled; (III) reviewed how sample repositories/databases are currently used; and, (IV) evaluated justifications for acquiring new samples. Each breakout session culminated with a discussion of (V) what important science questions could be addressed soon (5–10 years), with existing or forthcoming assets and technologies, versus (VI) what might take longer (10+ years) and/or require the development of new assets or technologies. These motivating topics fed into the second day of discussions, which focused on “Aligning seafloor sampling technology with critical science questions.” Groups were guided by a common set of prompts, including what current resources were essential to the participants’ research, and what were the greatest challenges they faced in recovering the materials needed. The participants also discussed whether they could acquire the materials needed to address their science questions given current US assets (Figure 1 in FUTURE 2024 PI-team, 2024, AGU Advances 2024AV001560), how sample repositories and databases could be optimized for science needs, and the justification for acquiring or developing new technologies.