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1. Indonesian Throughflow

   https://doi.org/10.14379/iodp.proc.356.2017  

   Gallagher, S.J. ; Fulthorpe, C.S. ; Bogus, K. ( February 2017 , Proceedings of the International Ocean Discovery Program)

   The Indonesian Throughflow (ITF) is a critical part of the global thermohaline conveyor. It plays a key role in transporting heat from the equatorial Pacific (the Indo-Pacific Warm Pool) to the Indian Ocean and exerts a major control on global climate. The complex tectonic history of the Indonesian archipelago, a result of continued northward motion and impingement of the Australasian plate into the southeast Asian part of the Eurasian plate, makes it difficult to reconstruct long-term (i.e., million year) ITF history from sites within the archipelago. The best areas to investigate ITF history are downstream in the Indian Ocean, either in the deep ocean away from strong tectonic deformation or along proximal passive margins that are directly under the influence of the ITF. Although previous Ocean Drilling Program and Deep Sea Drilling Project deep-water cores recovered in the Indian Ocean have been used to chart Indo-Pacific Warm Pool influence and, by proxy, ITF variability, these sections lack direct biogeographic and sedimentological evidence of the ITF. International Ocean Discovery Program Expedition 356 cored seven sites covering a latitudinal range of 29°S–18°S off the northwest coast of Australia to obtain a 5 My record of the ITF, Indo-Pacific Warm Pool, and climate evolution that has the potential to match orbital-scale deep-sea records in its resolution. The material recovered will allow us to describe the history of the Australian monsoon and its variability, a system whose genesis is thought to be related to the initiation of the East Asian monsoon and is hypothesized to have been in place since the Pliocene or earlier. It also will lead to a better understanding of the nature and timing of the development of aridity on the Australian continent. Detailed paleobathymetric and stratigraphic data from the transect will also allow subsidence curves to be constructed to constrain the spatial and temporal patterns of vertical motions caused by the interaction between plate motion and convection within the Earth’s mantle, known as dynamic topography. The northwest shelf is an ideal location to study this phenomenon because it is positioned on the fastest moving continent since the Eocene, on the edge of the degree 2 geoid anomaly. Accurate subsidence analyses over 10° of latitude can resolve whether northern Australia is moving with or over either a time-transient or long-term stationary downwelling within the mantle, thereby vastly improving our understanding of deep-Earth dynamics and their impact on surficial processes. 

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2. Expedition 356 Scientific Prospectus: Reefs, Oceans, and Climate

   https://doi.org/10.14379/iodp.sp.356.2014  

   Gallagher, S.J. ; Fulthorpe, C.S. ; Bogus, K.A. ( August 2014 , Scientific prospectus)

   null (Ed.)

   The Indonesian Throughflow (ITF) is a critical part of the global thermohaline conveyor. It plays a key role in transporting heat from the equatorial Pacific (the Indo-Pacific Warm Pool) to the Indian Ocean and exerts a major control on global climate. The complex tectonic history of the Indonesian Archipelago, a result of continued northward motion and impingement of the Australasian Plate into the Southeast Asian part of the Eurasian Plate, makes it difficult to reconstruct long-term (i.e., million year) ITF history from sites within the archipelago. The best areas to investigate ITF history are downstream in the Indian Ocean, either in the deep ocean away from strong tectonic deformation or along proximal passive margins that are directly under the influence of the ITF. Although previous Ocean Drilling Program and Deep Sea Drilling Project deepwater cores recovered in the Indian Ocean have been used to chart Indo-Pacific Warm Pool influence and, by proxy, ITF variability, these sections lack direct biogeographic and sedimentological evidence of the ITF. International Ocean Discovery Program Expedition 356 will drill a transect of cores over 10° latitude on the northwest shelf (NWS) of Australia to obtain a 5 m.y. record of ITF, Indo-Pacific Warm Pool, and climate evolution that has the potential to match orbital-scale deep-sea records in its resolution. Coring the NWS will reveal a detailed shallow-water history of ITF variability and its relationship to climate. It will allow us to understand the history of the Australian monsoon and its variability, a system whose genesis is thought to be related to the initiation of the East Asian monsoon and is hypothesized to have been in place since the Pliocene or earlier. It also will lead to a better understanding of the nature and timing of the development of aridity on the Australian continent. Detailed paleobathymetric and stratigraphic data from the transect will also allow subsidence curves to be constructed to constrain the spatial and temporal patterns of vertical motions caused by the interaction between plate motion and convection within the Earth’s mantle, known as dynamic topography. The NWS is an ideal location to study this phenomenon because it is positioned on the fastest moving continent since the Eocene, on the edge of the degree two geoid anomaly. Accurate subsidence analyses over 10° of latitude can resolve whether northern Australia is moving with/over a time-transient or long-term stationary downwelling within the mantle, thereby vastly improving our understanding of deep-Earth dynamics and their impact on surficial processes. 

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3. 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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4. 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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5. Expedition 371 Scientific Prospectus: Tasman Frontier Subduction Initiation and Paleogene Climate

   https://doi.org/10.14379/iodp.sp.371.2016  

   Sutherland, R. ; Dickens, G.R. ; Blum, P. ( December 2016 , Scientific prospectus)

   null (Ed.)

   During International Ocean Discovery Program Expedition 371, we will core and log Paleogene and Neogene sediment sequences within the Tasman Sea. The cores will be analyzed for their sediment composition, microfossil components, mineral and water chemistry, and physical properties. The research will improve our understanding of how convergent plate boundaries form, how greenhouse climate systems work, and how and why global climate has evolved over the last 60 my. The most profound subduction initiation event and global plate-motion change since 80 Ma appears to have occurred in the early Eocene, when Tonga-Kermadec and Izu-Bonin-Mariana subduction initiation corresponded with a change in direction of the Pacific plate (Emperor-Hawaii bend) at ~50 Ma. The primary goal of Expedition 371 is to precisely date and quantify deformation and uplift/subsidence associated with Tonga-Kermadec subduction initiation in order to test predictions of alternate geodynamic models. This tectonic change may coincide with the pinnacle of Cenozoic “greenhouse” climate. However, paleoclimate proxy data from lower Eocene strata in the southwest Pacific show especially warm conditions, presenting a significant discrepancy with climate model simulations. The second goal is to determine if paleogeographic changes caused by subduction initiation may have led to anomalous regional warmth by altering ocean circulation. Late Neogene sediment cores will complement earlier drilling to investigate the third goal: tropical and polar climatic teleconnections. During Expedition 371, we will drill in a significant midlatitude transition zone influenced by both the Antarctic Circumpolar Current and the Eastern Australian Current. The accumulation of relatively thick carbonate-rich Neogene bathyal strata make this a good location for generating detailed paleoceanographic records from the Miocene through the Pleistocene that can be linked to previous ocean drilling expeditions in the region (Deep Sea Drilling Project Legs 21, 29, and 90; Ocean Drilling Program Leg 189) and elsewhere in the Pacific Ocean. 

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