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Journal articleHollyday A, Raymo ME, Austermann J, et al., 2024,
Pliocene shorelines and the epeirogenic motion of continental margins: a target dataset for dynamic topography models
, Earth Surface Dynamics, Vol: 12, Pages: 883-905, ISSN: 2196-6311Global mean sea level during the mid-Pliocene epoch (ĝ1/43 Ma), when CO2 and temperatures were above present levels, was notably higher than today due to reduced global ice sheet coverage. Nevertheless, the extent to which ice sheets responded to Pliocene warmth remains in question owing to high levels of uncertainty in proxy-based sea level reconstructions as well as solid Earth dynamic models that have been used to evaluate a limited number of data constraints. Here, we present a global dataset of 10 wave-cut scarps that formed by successive Pliocene sea level oscillations and which are observed today at elevations ranging from ĝ1/46 to 109 m above sea level. The present-day elevations of these features have been identified using a combination of high-resolution digital elevation models and field mapping. Using the MATLAB interface TerraceM, we extrapolate the cliff and platform surfaces to determine the elevation of the scarp toe, which in most settings is buried under meters of talus. We correct the scarp-toe elevations for glacial isostatic adjustment and find that this process alone cannot explain observed differences in Pliocene paleo-shoreline elevations around the globe. We next determine the signal associated with mantle dynamic topography by back-advecting the present-day three-dimensional buoyancy structure of the mantle and calculating the difference in radial surface stresses over the last 3 Myr using the convection code ASPECT. We include a wide range of present-day mantle structures (buoyancy and viscosity) constrained by seismic tomography models, geodynamic observations, and rock mechanics laboratory experiments. Finally, we identify preferred dynamic topography change predictions based on their agreement with scarp elevations and use our most confident result to estimate a Pliocene global mean sea level based on one scarp from De Hoop, South Africa. This inference (11.6 ± 5.2 m) is a downward revision and may imply that ice sheets were rela
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Journal articleWilson Kemsley S, Ceppi P, Andersen H, et al., 2024,
A systematic evaluation of high-cloud controlling factors
, Atmospheric Chemistry and Physics, Vol: 24, Pages: 8295-8316, ISSN: 1680-7316Clouds strongly modulate the top-of-the-atmosphere energy budget and are a major source of uncertainty in climate projections. "Cloud controlling factor"(CCF) analysis derives relationships between large-scale meteorological drivers and cloud radiative anomalies, which can be used to constrain cloud feedback. However, the choice of meteorological CCFs is crucial for a meaningful constraint. While there is rich literature investigating ideal CCF setups for low-level clouds, there is a lack of analogous research explicitly targeting high clouds. Here, we use ridge regression to systematically evaluate the addition of five candidate CCFs to previously established core CCFs within large spatial domains to predict longwave high-cloud radiative anomalies: upper-tropospheric static stability (SUT), sub-cloud moist static energy, convective available potential energy, convective inhibition, and upper-tropospheric wind shear (ΔU300). We identify an optimal configuration for predicting high-cloud radiative anomalies that includes SUT and ΔU300 and show that spatial domain size is more important than the selection of CCFs for predictive skill. We also find an important discrepancy between the optimal domain sizes required for predicting locally and globally aggregated radiative anomalies. Finally, we scientifically interpret the ridge regression coefficients, where we show that SUT captures physical drivers of known high-cloud feedbacks and deduce that the inclusion of SUT into observational constraint frameworks may reduce uncertainty associated with changes in anvil cloud amount as a function of climate change. Therefore, we highlight SUT as an important CCF for high clouds and longwave cloud feedback.
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ReportJennings N, Brandmayr C, 2024,
How can action to tackle climate change improve people’s health and save the NHS money?
To achieve Net Zero greenhouse gas emissions by 2050 and contribute to global efforts to avoid the worst consequences of climate change, policies are required that reduce emissions across the whole of UK society including the transport, housing and agriculture sectors. Climate action could play an important role in helping to reduce existing health inequalities, improving public health and responding to the high levels of pressure on the NHS.
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ReportLawrance E, Newberry Le Vay J, El Omrani O, et al., 2024,
Global Agenda for Research and Action in Climate Change and Mental Health
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Journal articleKlages JP, Hillenbrand C-D, Bohaty SM, et al., 2024,
Ice sheet-free West Antarctica during peak early Oligocene glaciation
, Science, Vol: 385, Pages: 322-327, ISSN: 0036-8075One of Earth's most fundamental climate shifts - the greenhouse-icehouse transition 34 Ma ago - initiated Antarctic ice-sheet build-up, influencing global climate until today. However, the extent of the ice sheet during the Early Oligocene Glacial Maximum (~33.7-33.2 Ma) that immediately followed this transition, a critical knowledge gap for assessing feedbacks between permanently glaciated areas and early Cenozoic global climate reorganization, is uncertain. Here, we present shallow-marine drilling data constraining earliest Oligocene environmental conditions on West Antarctica's Pacific margin - a key region for understanding Antarctic ice sheet-evolution. These data indicate a cool-temperate environment, with mild ocean and air temperatures preventing West Antarctic Ice Sheet formation. Climate-ice sheet modeling corroborates a highly asymmetric Antarctic ice sheet, thereby revealing its differential regional response to past and future climatic change.
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OtherKokkola H, Tonttila J, Calderón S, et al., 2024,
Supplementary material to "Model analysis of biases in satellite diagnosed aerosol effect on cloud liquid water path"
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OtherSteinbruegge G, Dunnigan A, King S, et al., 2024,
Geodetic Contributions of the VenSAR Instrument for Inferring the Interior Structure of Venus
<jats:p>Introduction:&#160; One of the science priorities of the EnVision mission is to infer the interior structure of Venus, including the properties and thicknesses of its crust, mantle, and core [1]. Measurements of the moment of inertia and length-of-day variations provide critical geodetic constraints to understand the bulk interior structure of the planet. The polar moment of inertia of Venus is inversely proportional to the precession rate.&#160;Measuring the precession rate directly from orbit is challenging. For Magellan, spacecraft ephemeris errors dominated the measurement errors and for EnVision very similar challenges are expected. The precession rate itself depends on a number of geodetic parameters, namely the orbital mean motion, the spin rate, the second-degree gravity coefficient, the total mass of the planet, the radius, and the obliquity. To constrain the inertia tensor of Venus and hence to meet the EnVision objectives, the gravity field information must be complemented by measurements of the rotational state. Therefore, augmenting the gravity science solution with surface feature tracking and/or altimetry &#8211; abilities that VenSAR offers &#8211; can be critical in achieving EnVision science objectives. VenSAR has the capability to make use of globally distributed VenSAR altimetry data and ground-track intersections (cross-over points) to create a dense geodetic net. These observations can be used in concert with gravity observations and SAR images (Figure 1) to improve the a posteriori orbit determination, to solve for the rotation state of Venus including spin axis orientation and precession, and to allow the co-registration of other data products generated by the EnVision mission via improving the overall reference frame of Venus. The precise measurement of the rotation state allows us to infer constraints on the interior structure (e.g., by inferring the moment of inertia) as has been recently demon
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OtherMcVann P, Ghail R, Mason P, et al., 2024,
The Creation of a Radiometric Correction Module in Python for Chandrayaan-2
<jats:p>Introduction: Synthetic Aperture Radar (SAR) is a powerful tool for the remote sensing of planetary surfaces. It allows for high resolution imaging of the surface at different wavelength ranges (or &#8216;bands&#8217;), each providing different information. The European Space Agency has an open-source toolbox named SNAP for the exploration of Earth Observation data. However, there is no equivalent open-source toolbox for non-terrestrial datasets. This project aims to begin the development of an open-source toolbox created for planetary missions, with an initial focus on the development of radiometric correction module for SAR data acquisitions from the ISRO&#8217;s Lunar, Chandrayaan-2 mission.Chandrayaan-2: Launched by the ISRO in 2019, Chandrayaan-2 is the first fully-polarimetric SAR to study the Moon. This allows for the gathering of detailed information on the properties of surficial elements such as the structure or the orientation. The Dual Frequency Synthetic Aperture Radar (DFSAR) onboard the satellite will image in both S- and L-Band frequencies, the latter allowing for shallow ~3m penetration into the Lunar surface [1]. This mission's main scientific goals are to create high-resolution maps of the polar regions, estimate the distribution and thickness of the regolith and to make a quantitative estimation of water-ice in the polar regions of the Moon.The Lunar South Pole: A heavily cratered region of great interest due to the suspected presence of water-ice in the permanently shadowed regions (PSRs.) It is also the location of candidate landing regions for NASA&#8217;s Artemis III mission. Evidence for the presence of subsurface water-ice has been provisionally interpreted from anomalies in UV and VIR albedo, and high Circular Polarisation Ratio (CPR) in remotely sensed data [2]. The initial data return of Chandrayaan-2 has indicated that craters in both PSRs and non-PSRs have anomalous CPR values in both the S
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Journal articleLester JG, Graven HD, Khatiwala S, et al., 2024,
Changes in Oceanic Radiocarbon and CFCs Since the 1990s
, Journal of Geophysical Research: Oceans, Vol: 129, ISSN: 2169-9275Anthropogenic perturbations from fossil fuel burning, nuclear bomb testing, and chlorofluorocarbon (CFC) use have created useful transient tracers of ocean circulation. The atmospheric 14C/C ratio (∆14C) peaked in the early 1960s and has decreased now to pre-industrial levels, while atmospheric CFC-11 and CFC-12 concentrations peaked in the early 1990s and early 2000s, respectively, and have now decreased by 10%–20%. We present the first analysis of a decade of new observations (2007 to 2018–2019) and give a comprehensive overview of the changes in ocean ∆14C and CFC concentration since the WOCE surveys in the 1990s. Surface ocean ∆14C decreased at a nearly constant rate from the 1990–2010s (20‰/decade). In most of the surface ocean ∆14C is higher than in atmospheric CO2 while in the interior ocean, only a few places are found to have increases in ∆14C, indicating that globally, oceanic bomb 14C uptake has stopped and reversed. Decreases in surface ocean CFC-11 started between the 1990 and 2000s, and CFC-12 between the 2000–2010s. Strong coherence in model biases of decadal changes in all tracers in the Southern Ocean suggest ventilation of Antarctic Intermediate Water was enhanced from the 1990 to the 2000s, whereas ventilation of Subantarctic Mode Water was enhanced from the 2000 to the 2010s. The decrease in surface tracers globally between the 2000 and 2010s is consistently stronger in observations than in models, indicating a reduction in vertical transport and mixing due to stratification.
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Journal articleMcLeod J, Whittaker AC, Bell RE, et al., 2024,
Landscapes on the edge: river intermittency in a warming world
, Geology, Vol: 52, Pages: 512-516, ISSN: 1943-2682Sediment transport in rivers is not steady through time. Highly intermittent river systems, which only transport bedload during the most significant flow events, are particularly sensitive to changes in climate and precipitation patterns. People and landscapes can be vulnerable to fluvial processes, and quantifying river intermittency is critical for assessing landscape response to projected changes in precipitation extremes due to climate change. We generated new constraints on recent to modern fluvial intermittency factors—the frequency at which bedload is mobilized in a river—based on field measurements in the Corinth Rift, Greece, and Holocene sediment accumulation rates. Results reveal some of the lowest documented intermittency factors to date, showing Mediterranean rivers can transport an entire annual sediment load in a rare storm event. Coupling intermittency calculations with historical flood and precipitation data indicates these rivers transport bedload during one storm every ∼4 yr, associated with rainfall >50 mm/d, and subsequent floods; this hydroclimate is typical across the Mediterranean region. Furthermore, climate models predict precipitation extremes will increase across Europe, and the frequency of events that surpass thresholds of sediment transport will increase significantly, potentially causing sediment loads to double by 2100 CE. As the area of arid land likely to host intermittent rivers also increases, sensitive landscapes are on the edge of significant geomorphic change, driven by global warming.
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