ALBERT

Description: Future sea-level rise projections are characterized by both quantifiable uncertainty and unquantifiable structural uncertainty. Thorough scientific assessment of sea-level rise projections requires analysis of both dimensions of uncertainty. Probabilistic sea-level rise projections evaluate the quantifiable dimension of uncertainty; comparison of alternative probabilistic methods provides an indication of structural uncertainty. Here we describe the Framework for Assessing Changes To Sea-level (FACTS), a modular platform for characterizing different probability distributions for the drivers of sea-level change and their consequences for global mean, regional, and extreme sea-level change. We demonstrate its application by generating seven alternative probability distributions under multiple emissions scenarios for both future global mean sea-level change and future relative and extreme sea-level change at New York City. These distributions, closely aligned with those presented in the Intergovernmental Panel on Climate Change Sixth Assessment Report, emphasize the role of the Antarctic and Greenland ice sheets as drivers of structural uncertainty in sea-level change projections.

Description: We present a new set of global and local sea‐level projections at example tide gauge locations under the RCP2.6, RCP4.5 and RCP8.5 emissions scenarios. Compared to the CMIP5‐based sea‐level projections presented in IPCC AR5, we introduce a number of methodological innovations, including: (i) more comprehensive treatment of uncertainties; (ii) direct traceability between global and local projections; (iii) exploratory extended projections to 2300 based on emulation of individual CMIP5 models. Combining the projections with observed tide gauge records, we explore the contribution to total variance that arises from sea‐level variability, different emissions scenarios and model uncertainty. For the period out to 2300 we further breakdown the model uncertainty by sea‐level component and consider the dependence on geographic location, time horizon and emissions scenario. Our analysis highlights the importance of variability for sea‐level change in the coming decades and the potential value of annual‐to‐decadal predictions of local sea‐level change. Projections to 2300 show a substantial degree of committed sea‐level rise under all emissions scenarios considered and highlights the reduced future risk associated with RCP2.6 and RCP4.5 compared to RCP8.5. Tide gauge locations can show large (〉 50%) departures from the global average, in some cases even reversing the sign of the change. While uncertainty in projections of the future Antarctic ice dynamic response tends to dominate post‐2100, we see a substantial differences in the breakdown of model variance as a function of location, timescale and emissions scenario.

Description: Boron is a fluid-mobile element whose isotopic composition reflects many factors that are relevant to understanding mineralizing processes, including fluid source(s), fluid-rock interaction, and mineralization temperature. The most important host of boron in hydrothermal mineral deposits is tourmaline, which is fortuitous because this is a very stable and chemically resistant mineral with a wide compositional range. We have compiled published B-isotope data of tourmaline from 110 hydrothermal deposits worldwide (〉2210 analyses) organized into seven groups: porphyry Cu-Mo-Au deposits, granite-related Sn-W deposits, IOCG deposits, orogenic Au deposits, stratabound VMS and SEDEX deposits, and sediment-hosted U deposits (Mendeley Data, V4, doi: 10.17632/tv5y7xt9fb.4). The total range of δ11B values for all deposits is -26.8 to +35.0 ‰. Four deposit types (granite Sn-W, orogenic Au, stratabound VMS and SEDEX) have median δ11B values close to the continental crustal average of ca. -10 ‰, whereas the median values for IOCG and porphyry Cu-Mo-Au deposits are higher (-3.9 ‰ and -2.1 ‰, respectively); the median for sediment-hosted U deposits is distinctly higher (+25.3 ‰). Importantly, each deposit type displays a considerable range of δ11B values, the smallest being 18 ‰ for granite Sn-W deposits and the largest (48 ‰) for IOCG deposits. These boron isotope ranges are suggested to reflect three levels of controlling factors. The primary one is the composition of the boron source; secondary effects relate to fluid-tourmaline fractionation (equilibrium or Rayleigh). There are commonly also tertiary factors that depend on evolution of the specific deposit, which include fluid mixing, changing water-rock ratio and/or depositional temperature, influences of other boron-bearing minerals, and where relevant, post-ore metamorphism. Separating the effects of these factors is rarely possible from boron isotopes alone, as selected case studies illustrate. However, multi-isotope studies of tourmaline, and approaches that combine isotopic and chemical variations in tourmaline can potentially overcome this limitation.

Description: A new compilation of published data on the boron isotope composition of hydrothermal tourmaline is presented here. The database is provided in the excel file (Trumbull_etal_B-isotopes_Tourmaline_OreDeposits.xlsx) and contains ca. 4000 boron isotope analyses of tourmaline gathered from 57 publications (see References.docx), as well as additional information about the deposit, host rocks, age and temperature of the mineralization, particulars of tourmaline occurrence, etc. The file permits filtering based on the data and all other attributes. Some filter options that may be useful are: “Publication”, “Deposit category”, “Country”, “Tourmaline host category”, “Tourmaline origin”, “Fluid source”, “Zoning”, “Mineralization”. It is important to note that the article linked to this database (“Application of boron isotopes in tourmaline to understanding hydrothermal ore systems” by Trumbull et al.; doi: https://doi.org/10.1016/j.oregeorev.2020.103682) discusses only tourmaline designated as “Hydrothermal” or “Hydrothermal?” in the database and reported in ISI-listed, English-language publications. This selection resulted in a total of 2622 d11B values reported in 49 publications. Cite this dataset Trumbull, Robert B.; Codeço, Marta S.; Jiang, Shao-Yong; Palmer, Martin R.; Slack, John F. (2020), “Boron isotopes in tourmaline from hydrothermal ore systems”, Mendeley Data, V4, doi: 10.17632/tv5y7xt9fb.4 Cite the article: Trumbull, Robert B.; Codeço, Marta S.; Jiang, Shao-Yong; Palmer, Martin R.; Slack, John F. (2020), “Boron isotope variations in tourmaline from hydrothermal ore deposits: A review of controlling factors and insights for mineralizing systems”, Ore Geology Reviews, 125: 103682, doi: https://doi.org/10.1016/j.oregeorev.2020.103682

Description: Tourmaline group minerals are typically the predominant host of boron in hydrothermal mineral deposits. Boron is a fluid-mobile element whose isotopic composition reflects many factors that are relevant to understanding mineralizing processes, including fluid source(s), fluid-rock interaction, and formational temperature. A new compilation of 2622 published δ11B values for tourmaline from diverse types of hydrothermal ore deposits is presented here, with the focus (2215 analyses) on seven main types: porphyry Cu-Mo-Au deposits, granite-related Sn-W deposits, IOCG deposits, orogenic Au deposits, stratabound VMS and SEDEX deposits, and sediment-hosted U deposits. The total range of δ11B values for the seven types is −26.8 to +35.0‰. Four (granite Sn-W, orogenic Au, stratabound VMS and SEDEX) have median δ 11B values close to the continental crustal average of about −10‰. The median values for IOCG and porphyry Cu-Mo-Au deposits are higher (−3.9‰ and −2.1‰, respectively), whereas sediment-hosted U deposits have distinctly high δ 11B (median = +25.3‰). Importantly, a considerable range of δ11B values exists for tourmaline within each deposit type, the smallest (17.8‰) for granite Sn-W deposits and the largest (48.0‰) for IOCG deposits. The boron isotope variations in tourmaline from different deposits are suggested to reflect three levels of controlling factors and how these factors operated is illustrated with a selected number of case studies. The primary factor is the composition of the boron source; secondary effects relate to fluid-tourmaline fractionation (equilibrium or Rayleigh). There are commonly also tertiary factors that depend on evolution of the specific deposit. These include fluid mixing, changing water–rock ratio and/or depositional temperature, influences of other boron-bearing minerals, and where relevant, post-ore metamorphism. Separating the effects of these factors is rarely possible from boron isotopes alone. However, the growth of multi-isotope studies of tourmaline and coexisting phases such as mica, as well as developments in modelling/experimentation of boron isotopes and element partitioning, suggest that this limitation will be overcome.

Description: The Otago Schist in New Zealand hosts orogenic tungsten (W) mineralization in two types. Proximally-sourced (“proximal”) mineralization in sub- to lower-greenschist facies Mesozoic metasedimentary rocks within the northern flank of the Otago Schist Belt comprise quartz-calcite veins with minor scheelite and few sulfides. Distally-sourced (“distal”) deposits are hosted in major crustal discontinuities within Mesozoic sub-greenschist to upper-greenschist facies metasedimentary rocks and are associated with abundant sulfides ± Au. In-situ trace element (particularly REE, Sr, Mo, Na, As) and in-situ 87Sr/86Sr compositions of scheelite show the scheelite occurring in these different mineralization types to be geochemically distinct. Proximal occurrences are characterised by scheelite with both heterogenous trace element and Sr isotope compositions displaying variations that can be linked to different veins, host rock types and scheelite generations. In contrast, scheelite within distal scheelite deposits tends to have fairly homogenous trace element and Sr isotopic ratios at the deposit to grain scale. The heterogenous compositions of proximal occurrences represent local derivation of diverse components from the sub-millimetre to meter scales and small extents of fluid flow, which resulted in a high sensitivity to sources and local rock compositions and thus limited large-scale equilibration of elemental and isotopic systematics within the scheelite they contain. The larger distal deposits formed by regional leaching by metamorphic fluids, probably at the greenschist-amphibolite facies boundary, followed by homogenisation as they ascended through the crust and leading to deposition of scheelite with rather uniform chemical characteristics. Our data re-enforce the model that tungsten mobility in the Otago Schist involved local-scale mobilisation of W in the shallow crust by breakdown of detrital rutile and scheelite at low metamorphic grade. Burial of these veined scheelite-bearing rocks to temperatures of ∼500 °C enabled remobilisation of W by metamorphic fluids, concurrent with scavenging of Au, As and S, followed by return of the metal-bearing fluids towards mid to upper crustal levels, where they precipitated scheelite.

Description: We present results of a storm surge simulation driven by the atmosphere of a climate model in which a catastrophic shutdown of the Atlantic Meridional Overturning Circulation (AMOC) is induced. Projections of change in the North Atlantic storm tracks in a warming world are highly uncertain and climate models show various responses. Atmospheric storms drive storm surges which are a major component of UK coastal flooding hazard, so it is important to ask how this process may be affected by climate change — not only what change is probable, but also what is possible? Our simulation is a contribution to answering that question. We also consider an ensemble simulation with a high-climate-sensitivity model under Representative Concentration Pathway 8.5 (RCP 8.5). We find significant simulated increases for some sites: up to about 0.4 metres increase (approximately 25%) in the expected annual maximum. In both the AMOC-collapse and the ensemble simulation, the largest projected increases appear at some west coast sites, associated with a growth in the strongest westerly winds. Projected changes on the south-east coast are smaller in the AMOC-collapse simulation and generally negative in the ensemble simulation, which exhibits a decrease in strong northerly winds in addition to the growth in westerlies. Overall, these increases due to atmospheric storminess change are smaller than the expected contribution from mean sea-level rise over the 21st century, but larger than the “high-end” changes due to atmospheric storminess change which were reported in UKCP18.

Description: The IPCC Sixth Assessment Report has highlighted the multi-century response time of global mean sea level rise associated with anthropogenic climate forcing since pre-industrial times. It is challenging to adequately assess future sea level rise impacts under different emissions scenarios due to large physical process uncertainties that rapidly increase over these timescales. Nevertheless, it is important to explore the multi-century sea level response due to the profound risks that sea level rise poses for low-lying coastal regions around the world. Here, we use two different climate and sea level emulators to investigate multi-century sea level rise commitments for cumulative emission levels at the start of the remaining 21st century decades under the five illustrative SSP-RCP scenarios. Preliminary results indicate that emissions until 2030 “lock in” around 0.61 m (66% model range: 0.33 to 0.91 m) of global mean sea level rise in 2300 relative to 1995-2014 under an intermediate emissions scenario (SSP2-4.5). Corresponding median global sea level commitments for cumulative emissions in 2050 (0.84 m) and 2100 (1.40 m) are around 0.18 m and 0.73 m higher than under a very low emissions scenario (SSP1-1.9). Global results are also downscaled to selected regional sites to illustrate locally-committed sea level rise. The presented work not only informs questions around how much sea level rise is “locked in” and could still be avoided through stringent mitigation but can also be used by practitioners to feed into assessments of minimum adaptation requirements.

Description: There is increasing awareness of the need for comprehensive information on potential future sea level rise to inform adaptation planning and coastal decision making. The IPCC Sixth Assessment Report (AR6) states that global mean sea level (GMSL) rise approaching 5 m by 2150, and more than 15 m by 2300, cannot be ruled out under high greenhouse gas emissions due to uncertainty in ice sheet processes. However, current guidance on high-end sea level rise for the United Kingdom (UK) advises users to plan for up to 1.9 m of sea-level rise by 2100 with no explicit consideration of long-term commitment. This work aims to provide a framework to accommodate updated high-end sea level rise guidance that extends to 2300. We combine the Monte Carlo methods used in the latest national sea level projections (UKCP18) with recently published projections of Antarctic ice mass loss to develop a small set of physically consistent storylines of local sea level rise. The storylines span the range of GMSL rise uncertainty at 2300 assessed by AR6 and provide continuous sea level rise information around the UK coast. For a given storyline, the relative contribution from Antarctica and Greenland is an important determinant of the UK rise. While we focus on the UK, the methods are generic and can be readily applied to other geographic locations.