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1. The Indo–Pacific Pollen Database – a Neotoma constituent database

   https://doi.org/10.5194/cp-20-2473-2024  

   Herbert, Annika V; Haberle, Simon G; Flantua, Suzette_G A; Mottl, Ondrej; Blois, Jessica L; Williams, John W; George, Adrian; Hope, Geoff S (January 2024, Climate of the Past)

   Abstract. The Indo–Pacific Pollen Database (IPPD) is the brainchild of the late professor Geoffrey Hope, who gathered pollen records from across the region to ensure their preservation for future generations of palaeoecologists. This noble aim is now being fulfilled by integrating the IPPD into the online Neotoma Paleoecology Database, making this compilation available for public use. Here we explore the database in depth and suggest directions for future research. The IPPD comprises 226 fossil pollen records, most postdating 20 ka but with some extending as far back as 50 ka or further. Over 80 % of the records are Australian, with a fairly even distribution between the different Australian geographical regions, with the notable exception being Western Australia, which is only represented by three records. The records are also well distributed in the modern climate space, with the largest gap being in drier regions due to preservation issues. However, many of the records contain few samples or have fewer than five chronology control points, such as radiocarbon, luminescence or Pb-210, for the younger sequences. Average deposition time for the whole database, counted as years per centimetre, is 64.8 yr cm−1, with 61 % of the records having a deposition time shorter than 50 yr cm−1. The slowest deposition time by geographical region occurs on Australia's east coast, while the fastest times are from the western Pacific. Overall, Australia has a slower deposition time than the rest of the Indo–Pacific region. The IPPD offers many exciting research opportunities to investigate past regional vegetation changes and associated drivers, including contrasting the impact of the first human arrival and European colonisation on vegetation. Examining spatiotemporal patterns of diversity and compositional turnover/rate of change, land cover reconstructions, and plant functional or trait diversity are other avenues of potential research, amongst many others. Merging the IPPD into Neotoma also facilitates inclusion of data from the Indo–Pacific region into global syntheses. 

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2. Western Pacific Warm Pool

   https://doi.org/10.14379/iodp.proc.363.2018  

   Rosenthal, Y.; Holbourn, A.E.; Kulhanek, D.K. (June 2018, Proceedings of the International Ocean Discovery Program)

   null (Ed.)

   International Ocean Discovery Program Expedition 363 sought to document the regional expression and driving mechanisms of climate variability (e.g., temperature, precipitation, and productivity) in the Indo-Pacific Warm Pool (IPWP) as it relates to the evolution of Neogene climate on millennial, orbital, and geological timescales. To achieve our objectives, we selected sites with a wide geographical distribution and variable oceanographic and depositional settings. Nine sites were cored during Expedition 363, recovering a total of 6956 m of sediment in 875–3421 m water depth with an average recovery of 101.3% during 39.6 days of on-site operations. Two moderate sedimentation rate (~3–10 cm/ky) sites are located off northwestern Australia at the southwestern maximum extent of the IPWP and span the late Miocene to present. Seven of the nine sites are situated at the heart of the Western Pacific Warm Pool (WPWP), including two sites on the northern margin of Papua New Guinea with very high sedimentation rates (>60 cm/ky) spanning the past ~450 ky, two sites in the Manus Basin (north of Papua New Guinea) with moderate sedimentation rates (~4–14 cm/ky) recovering upper Pliocene to present sequences, and three sites with low sedimentation rates (~1–3 cm/ky) on the southern and northern Eauripik Rise spanning the early Miocene to present. The wide spatial distribution of the cores, variable accumulation rates, exceptional biostratigraphic and paleomagnetic age constraints, and mostly excellent or very good foraminifer preservation will allow us to trace the evolution of the IPWP through the Neogene at different temporal resolutions, meeting the primary objectives of Expedition 363. Specifically, the high–sedimentation rate cores off Papua New Guinea will allow us to better constrain mechanisms influencing millennial-scale variability in the WPWP, their links to high-latitude climate variability, and implications for temperature and precipitation in this region under variable mean-state climate conditions. Furthermore, the high accumulation rates offer the opportunity to study climate variability during previous warm periods at a resolution similar to that of existing studies of the Holocene. With excellent recovery, Expedition 363 sites are suitable for detailed paleoceanographic reconstructions at orbital and suborbital resolution from the middle Miocene to Pleistocene and thus will be used to refine the astronomical tuning, biostratigraphy, magnetostratigraphy, and isotope stratigraphy of hitherto poorly constrained intervals within the Neogene timescale (e.g., the late Miocene) and to reconstruct the history of the Asian-Australian monsoon and the Indonesian Throughflow on orbital and tectonic timescales. Results from high-resolution interstitial water sampling at selected sites will be used to reconstruct density profiles of the western equatorial Pacific deep water during the Last Glacial Maximum. Additional geochemical analyses of interstitial water samples in this tectonically active region will be used to investigate volcanogenic mineral and carbonate weathering and their possible implications for the evolution of Neogene climate. 

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3. Expedition 363 Preliminary Report: Western Pacific Warm Pool

   https://doi.org/10.14379/iodp.pr.363.2017  

   Rosenthal, Y.; Holbourn, A.E.; Kulhanek, D.K. (February 2017, Preliminary report)

   null (Ed.)

   International Ocean Discovery Program Expedition 363 sought to document the regional expression and driving mechanisms of climate variability (e.g., temperature, precipitation, and productivity) in the Western Pacific Warm Pool (WPWP) as it relates to the evolution of Neogene climate on millennial, orbital, and geological timescales. To achieve our objectives, we selected sites with wide geographical distribution and variable oceanographic and depositional settings. Nine sites were cored during Expedition 363, recovering a total of 6956 m of sediment in 875–3421 m water depth with an average recovery of 101.3% during 39.6 days of on-site operations. Two sites are located off northwestern Australia at the southern extent of the WPWP and span the late Miocene to present. Seven sites are situated at the heart of the WPWP, including two sites on the northern margin of Papua New Guinea (PNG) with very high sedimentation rates spanning the past ~450 ky, two sites in the Manus Basin north of PNG with moderate sedimentation rates recovering upper Pliocene to present sequences, and three low sedimentation rate sites on the southern and northern parts of the Eauripik Rise spanning the early Miocene to present. The wide spatial distribution of the cores, variable accumulation rates, exceptional biostratigraphic and paleomagnetic age constraints, and mostly excellent foraminifer preservation will allow us to trace the evolution of the WPWP through the Neogene at different temporal resolutions, meeting the primary objectives of Expedition 363. Specifically, the high sedimentation–rate cores off PNG will allow us to better constrain mechanisms influencing millennial-scale variability in the WPWP, their links to high-latitude climate variability, and implications for temperature and precipitation variations in this region under variable climate conditions. Furthermore, these high accumulation rates offer the opportunity to study climate variability during previous warm periods at a resolution similar to existing studies of the Holocene. With excellent recovery, Expedition 363 sites are suitable for detailed paleoceanographic reconstructions at orbital and suborbital resolution from the middle Miocene to Pleistocene, and thus will be used to refine the astronomical tuning, magneto-, isotope, and biostratigraphy of hitherto poorly constrained intervals within the Neogene timescale (e.g., the late Miocene) and to reconstruct the history of the East Asian and Australian monsoon and the Indonesian Throughflow on orbital and tectonic timescales. Results from high-resolution interstitial water sampling at selected sites will be used to reconstruct density profiles of the western equatorial Pacific deep water during the Last Glacial Maximum. Additional geochemical analyses of interstitial water samples in this tectonically active region will be used to investigate volcanogenic mineral and carbonate weathering and their possible implications for the evolution of Neogene climate. 

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4. Improving Australian Rainfall Prediction Using Sea Surface Salinity

   https://doi.org/10.1175/JCLI-D-20-0625.1  

   Rathore, Saurabh; Bindoff, Nathaniel L.; Ummenhofer, Caroline C.; Phillips, Helen E.; Feng, Ming; Mishra, Mayank (April 2021, Journal of Climate)

   null (Ed.)

   Abstract This study uses sea surface salinity (SSS) as an additional precursor for improving the prediction of summer [December–February (DJF)] rainfall over northeastern Australia. From a singular value decomposition between SSS of prior seasons and DJF rainfall, we note that SSS of the Indo-Pacific warm pool region [SSSP (150°E–165°W and 10°S–10°N) and SSSI (50°–95°E and 10°S–10°N)] covaries with Australian rainfall, particularly in the northeast region. Composite analysis that is based on high or low SSS events in the SSSP and SSSI regions is performed to understand the physical links between the SSS and the atmospheric moisture originating from the regions of anomalously high or low, respectively, SSS and precipitation over Australia. The composites show the signature of co-occurring La Niña and negative Indian Ocean dipole with anomalously wet conditions over Australia and conversely show the signature of co-occurring El Niño and positive Indian Ocean dipole with anomalously dry conditions there. During the high SSS events of the SSSP and SSSI regions, the convergence of incoming moisture flux results in anomalously wet conditions over Australia with a positive soil moisture anomaly. Conversely, during the low SSS events of the SSSP and SSSI regions, the divergence of incoming moisture flux results in anomalously dry conditions over Australia with a negative soil moisture anomaly. We show from the random-forest regression analysis that the local soil moisture, El Niño–Southern Oscillation (ENSO), and SSSP are the most important precursors for the northeast Australian rainfall whereas for the Brisbane region ENSO, SSSP, and the Indian Ocean dipole are the most important. The prediction of Australian rainfall using random-forest regression shows an improvement by including SSS from the prior season. This evidence suggests that sustained observations of SSS can improve the monitoring of the Australian regional hydrological cycle. 

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5. Arctic shrub colonization lagged peak postglacial warmth: Molecular evidence in lake sediment from Arctic Canada

   https://doi.org/10.1111/gcb.14836  

   Crump, Sarah E.; Miller, Gifford H.; Power, Matthew; Sepúlveda, Julio; Dildar, Nadia; Coghlan, Megan; Bunce, Michael (October 2019, Global Change Biology)

   Abstract Arctic shrubification is an observable consequence of climate change, already resulting in ecological shifts and global‐scale climate feedbacks including changes in land surface albedo and enhanced evapotranspiration. However, the rate at which shrubs can colonize previously glaciated terrain in a warming world is largely unknown. Reconstructions of past vegetation dynamics in conjunction with climate records can provide critical insights into shrubification rates and controls on plant migration, but paleoenvironmental reconstructions based on pollen may be biased by the influx of exotic pollen to tundra settings. Here, we reconstruct past plant communities using sedimentary ancient DNA (sedaDNA), which has a more local source area than pollen. We additionally reconstruct past temperature variability using bacterial cell membrane lipids (branched glycerol dialkyl glycerol tetraethers) and an aquatic productivity indicator (biogenic silica) to evaluate the relative timing of postglacial ecological and climate changes at a lake on southern Baffin Island, Arctic Canada. ThesedaDNA record tightly constrains the colonization of dwarf birch (Betula, a thermophilous shrub) to 5.9 ± 0.1 ka, ~3 ka after local deglaciation as determined by cosmogenic¹⁰Be moraine dating and >2 ka later thanBetulapollen is recorded in nearby lake sediment. We then assess the paleovegetation history within the context of summer temperature and find that paleotemperatures were highest prior to 6.3 ka, followed by cooling in the centuries precedingBetulaestablishment. Together, these molecular proxies reveal thatBetulacolonization lagged peak summer temperatures, suggesting that inefficient dispersal, rather than climate, may have limited Arctic shrub migration in this region. In addition, these data suggest that pollen‐based climate reconstructions from high latitudes, which rely heavily on the presence and abundance of pollen from thermophilous taxa likeBetula, can be compromised by both exotic pollen fluxes and vegetation migration lags. 

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