Physical Landscape and Environmental Change

Overview

The state of our physical environment affects our livelihood and well-being. Our common sustainable future depends on how we understand and manage environmental changes that occur in all spatial and temporal time scales. In this research cluster, we engage multidisciplinary initiatives and collaborate with emerging countries to study physical landscape and environmental changes. Using our cutting-edge research outcomes, we explore and provide sustainable solutions to our changing environments. Our research projects aim to:

(1) understand local and global changes in geological past and in human history;

(2) apply the latest field monitoring techniques to evaluate ecological well-being and health risk; and

(3) employ high-performance computing to investigate complex hydroclimatic changes.

Featured Research

GRF Project (PI: Prof Bernie Owen) Temporal Variations in the Controls of Lacustrine Sedimentation During Continental Rift Evolution: Evidence from the Northern Kenya Rift Valley

This study examines rock and sediment outcrops ranging in age from the Miocene to the present (~15–0 million years) in two areas of the northern Kenya Rift Valley.

This study will examine rock and sediment outcrops ranging in age from the Miocene to the present (~15–0 million years) in two areas of the northern Kenya Rift Valley. These include the arid Suguta Valley and, to the southwest, the eroded Tugen Hills. Both areas contain well-exposed deposits laid down in a variety of terrestrial and aquatic environments. This investigation will focus on those deposits formed in spring systems and fresh to saline lakes. The research will pursue four major lines of investigation: 1) a study of modern hot and cold springs and their deposits in the Suguta Valley; 2) characterising modern sedimentation in permanent and ephemeral lakes in the Suguta Valley, as well as changes in water chemistry between spring and river sources and modern saline lakes of the Suguta; 3) An investigation of past environments and sediments formed in ancient fresh to saline lakes that date back several million years in both the Suguta Valley and the Tugen Hills; and 4) integrating information on ancient and modern lakes in the northern Kenya Rift in order to determine if their are any systematic changes that can be related to rifting and volcanism in an evolving rift valley. The project will explore these major aims through field studies and systematic analyses of water (modern lake waters, rivers, springs and groundwater inflows) and sediment (outcrops, short cores) samples. We will provide field descriptions of sediment sequences and return samples for geochemical, sedimentological and diatom analyses. The results of this work will allow us to characterise the modern environments and to decipher the past depositional settings in which ancient sediments accumulated. In previous studies of the southern Kenya Rift, two members of the research team have detected many changes in the types of sediment that have accumulated at different times. These changes in deposition partly reflect varying past climates, but also mirror changes in the stage of development of the rift valley. This study will allow the research team to explore if their are similar, or different, long-term variations in deposition that may reflect changes in the evolving northern Kenya Rift and its tectonic setting and volcanic environments. We will then combine models from our earlier studies in the southern Kenya Rift with new models from this investigation in order to develop a broader-based understanding of how sedimentation changes with time in an evolving rift system.

Early Career Scheme (PI: Dr Jianfeng Li) Co-occurrence of Droughts and Heat Waves under the Changing Climate in the Pearl River Basin: Variations, Interactions and Impacts

This study investigates the changes, interactions and impacts of the co-occurrence of droughts and heat waves across the PRB under the changing climate.

Increases in air temperature and changes in precipitation regimes caused by global warming lead to considerable variations in heat waves and droughts, two of the most costly natural hazards for society. Droughts and heat waves are mainly caused by large-scale abnormal weather systems, such as ENSO and Atlantic Multi-decadal Oscillation. At the same time, the land-atmosphere interactions between droughts and heat waves can enhance each other. Such co-occurrences of droughts and heat waves are self-perpetuating and often associated with record-breaking drought-heat wave events. Although investigations of co-occurrence events have been conducted over Europe and the United States, similar studies for the Pearl River Basin (PRB), which is under a different climate system, are very limited. The PRB is located in the south China under subtropical monsoon climate and plays an indispensable role in providing water resources for the socioeconomic development of the Pearl River Delta (PRD), Hong Kong and Macau. Although the PRB is usually considered as with abundant precipitation, the high water demand and large population coupled with the changing climate make the PRB vulnerable to both droughts and heat waves. Droughts can cause salinity intrusion by seawater as water tables fall and thus causes threats to coastal drinking water supply, as well as adverse impacts on agricultural productivity, shipping and hydropower generation across the PRB, and heat waves can trigger heat-related diseases and deaths. The proposed study will investigate the changes, interactions and impacts of the co-occurrence of droughts and heat waves across the PRB under the changing climate. Datasets for observations, reanalysis data and Global Climate Model (GCM) outputs will be developed. The Variable Infiltration Capacity (VIC) and Weather Research and Forecasting model (WRF) will be configured for the PRB to simulate droughts and heat waves and conduct sensitivity experiments of the land-atmosphere interactions. The objectives of the proposed study are three-fold: (1) to characterize the spatio-temporal changes in the duration, intensity and joint return period of the co-occurrence across the PRB during the 21st century; (2) to analyze the sensitivity of land-atmosphere interactions to the development and evolution of the co-occurrence events under the changing climate, and; (3) to evaluate the impacts of the co-occurrence on society in terms of affected areas and heat stress to humans with the consideration of humidity. The expected outcomes of the proposed study will help decision makers to make predictions, give early warning, and plan for potential extreme drought-heat wave events.

Featured Publications

Bicarbonate-rich source waters were needed to form the largest sodium carbonate evaporite deposits in the geologic record, the early and middle Eocene Green River trona (NaHCO3·Na2CO3·2H2O) in the Bridger basin, Wyoming, and nahcolite (NaHCO3) in the Piceance Creek basin, Colorado. Large modern and Pleistocene trona deposits are associated with magmatic activity and Na⁺-HCO3⁻-rich hydrothermal inflow waters, either within the depositional basin (Lake Magadi, Kenya) or at great distances (Searles Lake, California). No evidence exists for magmatic sources of CO2 near the Green River Formation. Several regional volcanic centers were active 300 km or more to the north, but drainage reconstructions show that waters from these areas did not discharge into the Green River Formation lakes during evaporite deposition. Alternatively, Na⁺-HCO3⁻-rich waters could have drained northwestward from the Colorado Mineral belt to the Bridger basin via the proposed Aspen River. A river originating in the Colorado Mineral belt (Sawatch uplift) could also have provided source waters to the Piceance Creek basin. Field evidence, however, has not yet documented these flow paths, and specific Eocene volcanic centers and hydrothermal source areas have yet to be identified.

Tree ring data provide proxy records of historical hydroclimatic conditions that are widely used for reconstructing precipitation time series. Most previous applications are limited to annual time scales, though information about daily precipitation would enable a range of additional analyses of environmental processes to be investigated and modelled. We used statistical downscaling to simulate stochastic daily precipitation ensembles using dendrochronological data from the western Canadian boreal forest. The simulated precipitation series were generally consistent with observed precipitation data, though reconstructions were poorly constrained during short periods of forest pest outbreaks. The proposed multiple temporal scale precipitation reconstruction can generate annual daily maxima and persistent monthly wet and dry episodes, so that the observed and simulated ensembles have similar precipitation characteristics (i.e. magnitude, peak, and duration)—an improvement on previous modelling studies. We discuss how ecological disturbances may limit reconstructions by inducing non-linear responses in tree growth, and conclude with suggestions of possible applications and further development of downscaling methods for dendrochronological data.

Changes in air temperature (AT), humidity and wind speed (Wind) affect apparent temperature (AP), the human-perceived equivalent temperature1–3. Here we show that under climate warming, both reanalysis data sets and Global Climate Model simulations indicate that AP has increased faster than AT over land. The faster increase in AP has been especially significant over low latitudes and is expected to continue in the future. The global land average AP increased at 0.04 °C per decade faster than AT before 2005. This trend is projected to increase to 0.06 °C (0.03–0.09 °C; minimum and maximum of the ensemble members) per decade and 0.17 °C (0.12–0.25 °C) per decade under the Representative Concentration Pathway 4.5 scenario (RCP4.5) and RCP8.5, respectively, and reduce to 0.02 °C (0–0.03 °C) per decade under RCP2.6 over 2006–2100. The higher increment in AP in summer daytime is more remarkable than in winter night-time and is most prominent over low latitudes. The summertime increases in AT-based thermal discomfort are projected to balance the wintertime decreases in AT-based discomfort over low and middle latitudes, while the summertime increases in AP-based thermal discomfort are expected to outpace the wintertime decreases in AP-based thermal discomfort. Effective climate change mitigation efforts to achieve RCP2.6 can considerably alleviate the faster increase in AP.Apparent temperature, the perceived temperature from air temperature, humidity and wind combined, is projected to increase faster than air temperature. Thermal discomfort will see greater increases in summertime, outweighing wintertime decreases.