ADMAP-2: The next-generation Antarctic magnetic anomaly map

The Antarctic Digital Magnetic Anomaly Project compiled the first international magnetic anomaly map of the Antarctic region south of 60\ubaS (ADMAP-1) some six years after its 1995 launch (Golynsky et al., 2001; Golynsky et al., 2007; von Frese et al., 2007). This magnetic anomaly compilation provided new insights into the structure and evolution of Antarctica, including its Proterozoic-Archaean cratons, Proterozoic-Palaeozoic orogens, Palaeozoic-Cenozoic magmatic arc systems, continental rift systems and rifted margins, large igneous provinces and the surrounding oceanic gateways. The international working group produced the ADMAP-1 database from more than 1.5 million line-kilometres of terrestrial, airborne, marine and satellite magnetic observations collected during the IGY 1957-58 through 1999. Since the publication of the first magnetic anomaly map, the international geomagnetic community has acquired more than 1.9 million line-km of new airborne and marine data. This implies that the amount of magnetic anomaly data over the Antarctic continent has more than doubled. These new data provide important constraints on the geology of the enigmatic Gamburtsev Subglacial Mountains and Prince Charles Mountains, Wilkes Land, Dronning Maud Land, and other largely unexplored Antarctic areas (Ferraccioli et al., 2011, Aitken et al., 2014 \u327 Mieth & Jokat, 2014, Golynsky et al., 2013). The processing of the recently acquired data involved quality assessments by careful statistical analysis of the crossover errors. All magnetic data used in the ADMAP-2 compilation were delivered as profiles, although several of them were in raw form. Some datasets were decimated or upward continued to altitudes of 4 km or higher with the higher frequency geological signals smoothed out. The line data used for the ADMAP-1 compilation were reprocessed for obvious errors and residual corrugations. The new near-surface magnetic data were corrected for the international geomagnetic reference field and diurnal effects, edited for high-frequency errors, and levelled to minimize line-correlated noise. The magnetic anomaly data collected mainly in the 21-st century clearly cannot be simply stitched together with the previous surveys. Thus, mutual levelling adjustments were required to accommodate overlaps in these surveys. The final compilation merged all the available aeromagnetic and marine grids to create the new composite grid of the Antarctic with minimal mismatch along the boundaries between the datasets. Regional coverage gaps in the composite grid will be filled with anomaly estimates constrained by both the near-surface data and satellite magnetic observations taken mainly from the CHAMP and Swarm missions. Magnetic data compilations are providing tantalizing new views into regional-scale subglacial geology and crustal architecture in interior of East and West Antarctica. The ADMAP-2 map provides a new geophysical foundation to better understand the geological structure and tectonic history of Antarctica and surrounding marine areas. In particular, it will provide improved constraints on the lithospheric transition of Antarctica to its oceanic basins, and thus enable improved interpretation of the geodynamic evolution of the Antarctic lithosphere that was a key component in the assembly and break-up of the Rodinia and Gondwana supercontinents. This work was supported by the Korea Polar Research Institute

The International Bathymetric Chart of the Arctic Ocean Version 4.0

Funder: The Nippon Foundation of Japan, grant Seabed 2030Funder: Open access funding provided by Stockholm UniversityAbstract: Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 × 200 m versus 500 × 500 m) and with individual depth soundings constraining three times more area of the Arctic Ocean (∼19.8% versus 6.7%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises ∼14.3% in Ver. 4.0 compared to ∼5.4% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet

Rationale for future Antarctic and Southern Ocean drilling

Valuable insights into future sensitivity of the Antarctic cryosphere to atmospheric and oceanic warming can be gained from the geologic record of past climatic warm intervals. Continental to deep ocean sediments provide records of contemporaneous changes in ice sheet extent and oceanographic conditions that extend back in time, including periods with atmospheric CO2 levels and temperatures similar to those likely to be reached in the next 100 years. The Circum-Antarctic region is under-sampled respect to scientific ocean drilling. However, recovery from glacially-influenced, continental shelf and rise sediments (expeditions ODP178, 188 and IODP 318), provided excellent records of Cenozoic climate and ice sheet evolution. The ANtarctic DRILLing program achieved >98% recovery on the Ross Sea shelf with a stable platform on fast ice with riser drilling technology. Newer technologies, such as the MeBo shallow drilling rig will further improve Antarctic margin drilling. Drilling around Antarctica in the past decades revealed cooling and regional ice growth during the Cenozoic, coupled with paleogeographic, CO2 atmosphere concentration and global temperature changes. Substantial progress has been made in dating sediments and in the interpretation of paleoclimate/paleoenvironmental proxies in Antarctic margin sediments (e.g. orbital scale variations in Antarctica’s cryosphere during the Miocene and Pliocene). Holocene ultra-high resolution shelf sections recently recovered can be correlated to the ice core record, to detect local mechanisms versus inter-hemispheric connections. While the potential for reconstructing past ice sheet history has been demonstrated through a careful integration of geological and geophysical data with numerical ice sheet modelling, uncertainties remain high due to the sparse geographic distribution of the records and the regional variability in the ice sheet’s response. Projects developed using a multi-leg, multi-platform approach (e.g. latitudinal and/or depth transects involving a combination of land/ice shelf, seabed, riser, and riserless drilling platforms) will likely make the most significant scientific advances. Fundamental hypothesis can be tested and accomplished by drilling depth transects from ice-proximal to ice-distal locations, that will enable researchers to link past perturbations in the ice sheet with Southern Ocean and global climate dynamics. The variable response of the ice sheet to ongoing climatic change mandates broad geographic drilling coverage, particularly in climatically sensitive regions, like those with large upstream drainage basins, whose marine terminus is presently melting, due to ocean, warming water impinging the continental shelf. Key transects were identified at community workshops (http://www.scar-ace.org) in the frame of the SCAR/ACE (Antarctic Climate Evolution) and PAIS (Past Antarctic Ice Sheet dynamics) programs. New proposals were then submitted to IODP in addition to the existing ones, including a large European component and MSP pre-proposals, in the frame of a scientific concerted strategy. Main questions underpinning future scientific drilling tied IODP Science themes: 1) How did and will the Antarctic Ice Sheets respond to elevated temperatures and atmospheric pCO2? What is the contribution of Antarctic ice to past and future sea level changes? 2) What was the timing of rifting and subsidence controlling the opening of ocean gateways and the initiation of the circumpolar current system and the onset of glaciations

The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0 – A new bathymetric compilation covering circum-Antarctic waters

The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0 is a new digital bathymetric model (DBM) portraying the seafloor of the circum-Antarctic waters south of 60° S. IBCSO is a regional mapping project of the General Bathymetric Chart of the Oceans (GEBCO). IBCSO Version 1.0 DBM has been compiled from all available bathymetric data collectively gathered by more than 30 institutions from 15 countries. These data include multibeam and single beam echo soundings, digitized depths from nautical charts, regional bathymetric gridded compilations, and predicted bathymetry. Specific gridding techniques were applied to compile the DBM from the bathymetric data of different origin, spatial distribution, resolution, and quality. The IBCSO Version 1.0 DBM has a resolution of 500 x 500 m, based on a polar stereographic projection, and is publicly available together with a digital chart for printing from the project website (www.ibcso.org) and at http://dx.doi.org/10.1594/PANGAEA.80573

The International Bathymetric Chart of the Arctic Ocean Version 4.0.

Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 × 200 m versus 500 × 500 m) and with individual depth soundings constraining three times more area of the Arctic Ocean (∼19.8% versus 6.7%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises ∼14.3% in Ver. 4.0 compared to ∼5.4% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet