Annual Resolution Research Articles

A new high resolution object-oriented approach to define the spatiotemporal dynamics of the cover-management factor in soil erosion modelling

The cover management factor (C-factor) calculation requires the assessment of the intra‐annual spatiotemporal variability of biomass cover, owed to the natural growth cycle of vegetation and the impact of agriculture on land cover. However, this is frequently omitted, and the vegetation conditions are approximated by assigning constant values to static classified Land Use/Land Cover (LULC) maps, such as the Coordination of Information on the Environment (CORINE) Land Cover (CLC). Using as test site the Sperchios River catchment, Central Greece, this study introduces a new approach to estimate C-factor in a spatiotemporally exhaustive manner. The goal is to increase estimation accuracy in erosion modelling applications. The C-factor computations are performed on monthly scale, based on LULC maps that portray the basin’s agricultural areas in unprecedented detail. The methodology involves the use of a biophysical index, namely Fraction of Vegetation Cover (Fcover) and empirical literature data on crop types. Fcover was developed from Sentinel-2 (S2) imagery in 10-m analysis. Such analysis (compared to the 300-m one provided by the EU) is a major improvement towards a more precise estimation of C-factor. The study identified the monthly C-factor fluctuation at basin scale, and the most susceptible months seasons at localities in terms of land cover/soil loss potential. The higher C-factor values were acquired in October and the lower in May. Mean annual (numerical) C-factor complies with the value of July. All monthly values are significantly higher – almost double – than the mean annual stationary one. The revealed patterns would not have been detected in a lower temporal (e.g., annual) resolution without the incorporation of vegetation density seasonality. The study shows high reproducibility and upscaling potential, as the utilized datasets are available in all European Union (EU) Member States, having similar structure, thus they can be harmonized towards a unified continental approach.

Reconstructing lake bottom water temperatures and their seasonal variability in the Dead Sea Basin during MIS5e

AbstractInterglacial periods are characterised by thick accumulations of halite units in the Dead Sea Basin. During these intervals, small water droplets (fluid inclusions, FIs) were entrapped in the halite crystals which serve as windows to estimate the chemistry and physical properties of the primary lake water conditions. Brillouin spectroscopy is used here to reconstruct annual resolution temperatures from a halite core section in the Dead Sea Basin during the onset of Marine Isotope Stage 5e (ca 130 ka) of the Last Interglacial. Lake bottom temperatures can be inferred based on the occurrence of coarse/fine halite facies, as observed today with the formation of equivalent halite facies during winter/summer seasons in the Dead Sea. A recurring increase in lake bottom temperatures is found along the direction of coarse halite layers in three successive years. Moreover, low FI entrapment temperatures were detected in layers of fine (cumulate) halite facies. These results imply a twofold stronger seasonality in the Dead Sea Basin compared to today, with colder winters at the onset of Marine Isotope Stage 5e. The results therefore highlight the potential of using cyclic salt deposits to reconstruct seasonal temperature variability for numerous evaporitic environments in the geological record.

Seasonal Tidewater Glacier Terminus Oscillations Bias Multi‐Decadal Projections of Ice Mass Change

AbstractNumerical, process‐based simulations of tidewater glacier evolution are necessary to project future sea‐level change under various climate scenarios. Previous work has shown that nonlinearities in tidewater glacier and ice stream dynamics can lead to biases in simulated ice mass change in the presence of noisy forcings. Ice sheet modeling projections that are used in the IPCC Assessment Report 6 (AR6) utilize atmospheric and oceanic forcings at annual temporal resolution, omitting any higher frequency forcings. Here, we quantify the effect of seasonal (<1 year) tidewater glacier terminus oscillations on decadal‐scale (30 years) mass change. We use an idealized geometry to mimic realistic tidewater glacier geometries and investigate the impact of the magnitude of seasonal oscillations, bed slope at the glacier terminus, and basal friction law. We find that omitting seasonal terminus motion results in biased mass change projections, with up to an 39% underestimate or 25% overestimate of mass loss when seasonality is neglected, depending on bed slope and magnitude of oscillations. The bias is most sensitive to the magnitude of the seasonal terminus oscillations and exhibits very little sensitivity to choice of friction law. Although omitting seasonal terminus motion may bias mass change projections of individual glaciers, further work is needed to investigate the impact on ice sheet mass change projections. In order to achieve this, seasonality in atmospheric and oceanic forcings must be adequately represented and observations of seasonal terminus positions and tidewater glacier thickness changes must be acquired to evaluate numerical models.

A multi-scale dendroclimatological analysis of four common species in the southern Canadian boreal forest

A comprehensive assessment of the tree growth/climate relationship was undertaken to better understand the potential impacts of climate change on the growth dynamics of four widespread and common boreal tree species, namely jack pine (Pinus banksiana), black spruce (Picea mariana), eastern larch (Larix laricina), and trembling aspen (Populus tremuloides), located at the southern limits of the Canadian boreal forest. Over intra-annual time scales, results show that precipitation is likely the main driver of stem radius change (∆R), with jack pine radius exhibiting the most consistent positive relationship. Precipitation had a stronger relationship with stem radius variation in black spruce and eastern larch during periods when volumetric water content (VWC) in the root zone was below average, pointing to the likelihood that certain species rely more heavily on available moisture in the uppermost layers of the soil column to replenish stem water, especially during extended dry periods. Warm air temperatures had an immediate negative impact on stem water content due to transpiration. This was most marked during periods of reduced moisture availability in the root zone, when trees are more susceptible to net water volume loss. During periods when moisture was not limiting, a positive relationship between lagged air temperature and ∆R was detected. Warm air temperatures may therefore play an important role in stimulating radial growth when moisture requirements are met. At annual temporal resolution, the growth/climate relationship changed over the lifetime of our study species. Over the last several decades, the relationship between precipitation and annual radial tree growth has weakened, while positive relationships between spring and summer air temperature and annual radial tree growth have emerged, likely signaling a decrease in moisture limitations, and a positive response to spring warming. Our findings reveal that boreal forest tree species may benefit from spring and summer warming over the near term, providing there is sufficient moisture to support growth. Over the long term, rates of evapotranspiration are expected to overshadow gains in moisture related to an increase in precipitation. Under these circumstances, we are likely to see reduced growth rates and an increasingly negative response of boreal tree species growth to warm air temperatures.

Accelerated change in the glaciated environments of western Canada revealed through trend analysis of optical satellite imagery

The retreat of mountain glaciers affects mountain hazards and hydrology, and new methods are needed to rapidly map glacier retreat at planetary scales. We automatically map 14,329 glaciers (30,063 km2) in British Columbia and Alberta, Canada, from 1984 to 2020 using satellite image archives from the Landsat 4, 5, 7 and 8 missions and reveal an acceleration in area loss that commenced in 2011. Glacier fragmentation, disappearance, and proglacial lake development also accelerated, as did the retreat of glaciers to higher elevations. Our annually-resolved method relies on the existence of previously published and manually validated glacier inventories from the mid-1980s and mid-2000's. Our methods performed well for clean ice glaciers, had occasional errors when proglacial lakes were present, and consistently underestimated the area of debris-covered glaciers. Clean ice glacier area loss accelerated sevenfold between the early [1984–2010] and late [2011−2020] epochs. This acceleration yielded rates of area shrinkage of −49 ± 7 km2 a−1 [early] and − 340 ± 40 km2 a−1 [late] with accelerated losses (32-fold increase) for small glaciers on Vancouver Island over the last decade. Glacier fragmentation accelerated from 26 ± 5.6 fragments a−1 to 88 ± 39 fragments a−1. About 1141 glaciers fell below our 0.05 km2 detection limit and so disappeared from our database, representing a loss of 8%. Proglacial lake area growth accelerated from 9.2 ± 1.1 km2 a−1 to 49 ± 4.5 km2 a−1. We also observed an acceleration in the upwards migration of median glacier elevations for clean ice glaciers from 0.31 ± 0.08 m a−1 to 4.7 ± 0.7 m a−1. Our workflow demonstrates the advantages of annual resolution glacier inventories and contributes towards the implementation of planetary mapping of glaciers and glacier attributes at annual resolution.

Seasonal sedimentation in saline Lake Shira (Siberia, Russia) and meromixis: implications for regional paleoclimate reconstructions

Abstract. Detailed studies of processes of sediment record formation are necessary for accurate sediment-derived paleo-environmental reconstructions. We conducted the multi-year seasonal sediment evolution of sediment fluxes of chemical elements, organic and inorganic carbon, total nitrogen, and photosynthetic pigments for a period from 2012 to 2017. In 2013, 2016, 2017, and 2018, we estimated the contents of photosynthetic pigments in the uppermost sediment layers frozen in situ with a freeze-corer. In 2015 and 2016, a rare event of transition from meromixis (i.e. long-term hypolimnetic anoxia) to holomixis was observed, which was accompanied by the temporary disappearance of hydrogen sulfide from the water column in spring and a decrease in hydrogen sulfide in other seasons compared to the meromictic state. We have demonstrated that okenone and Mo in the Lake Shira sediments reflect the presence of hydrogen sulfide in the water column. However, the okenone showed smoothened multi-year dynamics without a pronounced seasonal one. Therefore, the okenone can be a proxy of sulphidic conditions in photic zone and weakly depend on seasons whereas Mo can be used as an indicator of winter periods when analyzed in cores with annual resolution. Sedimentation fluxes of other substances showed typical seasonal dynamics with a minimum in winter and a maximum in late summer and autumn. All chemical elements in the sedimentation flow can be roughly divided into those associated with organic matter and terrigenous-chemogenous. The components of the second group showed a pronounced peak of sedimentation in autumn 2012 and summer 2017 presumably due to the increased amount of precipitation at that time. This demonstrates the relationship between the terrigenous components and the climate humidity for this lake. Besides, it reflects the irregularity of annual varves composition.

Will the construction of high-speed rail accelerate urban land expansion? Evidences from Chinese cities

While the existing literature has investigated the influence of high-speed rail (HSR) on urban economic outcomes, relatively little is known about the influence of HSR on urban land expansion mainly due to the lack of long-term and high-resolution urban land use data. Taking an example of Chinese cities which have made tremendous progress in the construction of HSR during the last decade, this study empirically documents the impact of HSR on urban land growth of Chinese cities by using a panel dataset containing annual 30-m resolution impervious surface data and socioeconomic variables from 2003 to 2015. The influence of HSR on urban land use is estimated by combining the approaches of propensity score matching and difference-in-difference analysis. Our empirical findings indicate that HSR has a significant and positive influence on urban land expansion, suggesting that cities are expected to experience faster urban land growth after the construction of HSR. In addition, HSR facilitates faster urban land expansion for cities in central and western China than those in eastern China, and faster urban land expansion for cities with lower development levels than those with higher development levels. Policymakers may need to consider the heterogeneous impacts of HSR on urban land expansion when introducing HSR to promote urban land development.

Application of CCM SOCOL-AERv2-BE to cosmogenic beryllium isotopes: description and validation for polar regions

Abstract. The short-living cosmogenic isotope 7Be, which is produced by cosmic rays in the atmosphere, is often used as a tracer for atmospheric dynamics, with precise and high-resolution measurements covering the recent decades. The long-living isotope 10Be, as measured in polar ice cores with an annual resolution, is a proxy for long-term cosmic-ray variability, whose signal can, however, be distorted by atmospheric transport and deposition that need to be properly modeled to be accounted for. While transport of 7Be can be modeled with high accuracy using the known meteorological fields, atmospheric transport of 10Be was typically modeled using case-study-specific simulations or simplified box models based on parameterizations. Thus, there is a need for a realistic model able to simulate atmospheric transport and deposition of beryllium with a focus on polar regions and (inter)annual timescales that is potentially able to operate in a self-consistent mode without the prescribed meteorology. Since measurements of 10Be are extremely laborious and hence scarce, it is difficult to compare model results directly with measurement data. On the other hand, the two beryllium isotopes are believed to have similar transport and deposition properties, being different only in production and lifetime, and thus the results of 7Be transport can be generally applied to 10Be. Here we present a new model, called CCM SOCOL-AERv2-BE, to trace isotopes of 7Be and 10Be in the atmosphere based on the chemistry–climate model (CCM) SOCOL (SOlar Climate Ozone Links), which has been improved by including modules for the production, deposition, and transport of 7Be and 10Be. Production of the isotopes was modeled for both galactic and solar cosmic rays by applying the CRAC (Cosmic Ray Atmospheric Cascade) model. Transport of 7Be was modeled without additional gravitational settling due to the submicron size of the background aerosol particles. An interactive deposition scheme was applied including both wet and dry deposition. Modeling was performed using a full nudging to the meteorological fields for the period of 2002–2008 with a spin-up period of 1996–2001. The modeled concentrations of 7Be in near-ground air were compared with the measured ones at a weekly time resolution in four nearly antipodal high-latitude locations: two in the Northern (Finland and Canada) and two in the Southern (Chile and the Kerguelen Islands) Hemisphere. The model results agree with the measurements in the absolute level within error bars, implying that the production, decay, and lateral deposition are correctly reproduced. The model also correctly reproduces the temporal variability of 7Be concentrations on annual and sub-annual scales, including the presence and absence of the annual cycle in the Northern and Southern Hemisphere, respectively. We also modeled the production and transport of 7Be for a major solar energetic particle event (SPE) on 20 January 2005, which appears insufficient to produce a measurable signal but may serve as a reference event for historically known extreme SPEs. Thus, a new full 3D time-dependent model, based on CCM SOCOL, of 7Be and 10Be atmospheric production, transport, and deposition has been developed. Comparison with real data on the 7Be concentration in the near-ground air validates the model and its accuracy.

Sea Ice Variability and Trends in the Western Indian Ocean Sector of Antarctica During the Past Two Centuries and Its Response to Climatic Modes

AbstractAntarctic sea ice is a critical component of the ocean‐climate system. Sea ice concentration (SIC) records of various oceanic sectors of Antarctica available since 1979 reveal dramatic changes in recent years; however, there is no consensus yet on drivers of sea ice variability, changes and their future projections. The lack of long‐term SIC records has impeded the quantification of sea ice variability, trends and various forcing factors and mechanisms. Here, we present a long‐term SIC record (1809−1993 CE) for the Western Indian Ocean Sector (WIOS) of Antarctica derived from a new ice core oxygen isotope (δ18O) record together with three available records from Dronning Maud Land (DML), East Antarctica. This long‐term SIC record at annual resolution reveals a significant decline during 1830–1884 CE with a rate of 0.58% ± 0.12% decade−1 followed by moderate increase during 1927–1993 CE with a rate of 0.24% ± 0.11% decade−1. Current satellite‐derived SIC records reveal an increase of 2.59 ± 0.86% decade−1 during 1994–2014 CE, which is unprecedented over the last two centuries as determined by the ice core‐derived SIC record. The satellite and ice core combined SIC record (1809−2019 CE) also reveals a significant increase in interannual variability at El Niño Southern Oscillation band and decadal variability at 16–32 years band in the last few decades. Our investigation suggests that wind‐driven sea‐ice dynamics associated with switching phases of Southern Annular Mode and remote teleconnections of Pacific oscillations largely control the interannual to decadal sea ice variability in this region.

Annual resolution records of sea-level change since AD 1850 reconstructed from coral δ18O from the South China Sea

Annual resolution records of sea-level change since AD 1850 reconstructed from coral δ18O from the South China Sea

Seasonal climate signals preserved in biochemical varves: insights from novel high-resolution sediment scanning techniques

Abstract. Varved lake sediments are exceptional archives of paleoclimatic information due to their precise chronological control and annual resolution. However, quantitative paleoclimate reconstructions based on the biogeochemical composition of biochemical varves are extremely rare, mainly because the climate–proxy relationships are complex and obtaining biogeochemical proxy data at very high (annual) resolution is difficult. Recent developments in high-resolution hyperspectral imaging (HSI) of sedimentary pigment biomarkers combined with micro X-ray fluorescence (µXRF) elemental mapping make it possible to measure the structure and composition of varves at unprecedented resolution. This provides opportunities to explore seasonal climate signals preserved in biochemical varves and, thus, assess the potential for annual-resolution climate reconstruction from biochemical varves. Here, we present a geochemical dataset including HSI-inferred sedimentary pigments and µXRF-inferred elements at very high spatial resolution (60 µm, i.e. > 100 data points per varve year) in varved sediments of Lake Żabińskie, Poland, over the period 1966–2019 CE. We compare these data with local meteorological observations to explore and quantify how changing seasonal meteorological conditions influenced sediment composition and varve formation processes. Based on the dissimilarity of within-varve multivariate geochemical time series, we classified varves into four types. Multivariate analysis of variance shows that these four varve types were formed in years with significantly different seasonal meteorological conditions. Generalized additive models (GAMs) were used to infer seasonal climate conditions based on sedimentary variables. Spring and summer (MAMJJA) temperatures were predicted using Ti and total C (Radj2=0.55; cross-validated root mean square error (CV-RMSE) = 0.7 ∘C, 14.4 %). Windy days from March to December (mean daily wind speed > 7 m s−1) were predicted using mass accumulation rate (MAR) and Si (Radj2=0.48; CV-RMSE = 19.0 %). This study demonstrates that high-resolution scanning techniques are promising tools to improve our understanding of varve formation processes and climate–proxy relationships in biochemical varves. This knowledge is the basis for quantitative high-resolution paleoclimate reconstructions, and here we provide examples of calibration and validation of annual-resolution seasonal weather inference from varve biogeochemical data.

Trees Talk Tremor—Wood Anatomy and Content Reveal Contrasting Tree‐Growth Responses to Earthquakes

AbstractLarge earthquakes can increase the amount of water feeding stream flows, raise groundwater levels, and thus grant plant roots more access to water in water‐limited environments. We examine growth and photosynthetic responses of Pine plantations to the Maule Mw 8.8 earthquake in headwater catchments of Chile's Coastal Range. We combine high‐resolution wood anatomic (lumen area) and biogeochemical ( of wood cellulose) proxies of daily to weekly tree growth sampled from trees on floodplains and close to ridge lines. We find that, immediately after the earthquake, at least two out of six tree trees on valley floors had increased lumen area and decreased , while trees on hillslopes had a reverse trend. Our results indicate a control of soil water on this response, largely consistent with models that predict how enhanced postseismic vertical soil permeability causes groundwater levels to rise on valley floors, but fall along the ridges. Statistical analysis with boosted regression trees indicates that streamflow discharge gained predictive importance for photosynthetic activity on the ridges, but lost importance on the valley floor after the earthquake. We infer that earthquakes may stimulate ecohydrological conditions favoring tree growth over days to weeks by triggering stomatal opening. The weak and short‐lived signals that we identified, however, show that such responses are only valid under water‐limited, rather than energy‐limited tree, growth. Hence, dendrochronological studies targeted at annual resolution may overlook some earthquake effects on tree vitality.

Application of nonlinear land use regression models for ambient air pollutants and air quality index

Air pollution is a major global environmental problem that affects health. In view of this, it is important to improve the prediction method of air pollutant concentrations to obtain accurate exposure estimates. Currently, land use regression (LUR) models are widely used to predict the fine-scale spatial variation of air pollutants. However, most of previous studies used linear regression methods such as generalized linear models (GLM) with less applicability to fit LUR models. Considering the potential nonlinear relationship between predictor variables, this study adopted generalized additive models (GAM) to derive LUR models of air pollutants (including PM2.5, PM10, CO, NO2, SO2, and O3) and air quality index (AQI) in Beijing with annual resolution. These models were based on routine monitoring data from 35 national regulatory monitoring sites and combined with a set of predictor variables such as land-use type, traffic and industrial emissions, population density, and meteorological factors. Results indicated that compared with traditional methods, the GAM approach significantly improved the performance of LUR models with explanatory power adjusted R2 levels ranging from 70 to 90%, and the cross-validation analysis also showed high prediction accuracy of the GAM approach. Besides, this approach emphasized the importance of meteorology in predicting air pollutant concentrations and AQI values. Generally, this study provides a feasible way to determine exposure assessment in heavily polluted cities and future support for long-term environmental epidemiological studies.

Variability of Antarctic sea ice extent over the past 200 years

While Arctic sea ice has been decreasing in recent decades that is largely due to anthropogenic forcing, the extent of Antarctic sea ice showed a positive trend during 1979–2015, followed by an abrupt decrease. The shortness of the satellite record limits our ability to quantify the possible contribution of anthropogenic forcing and internal variability to the observed Antarctic sea ice variability. In this study, ice core and fast ice records with annual resolution from six sites are used to reconstruct the annual-resolved northernmost latitude of sea ice edge (NLSIE) for different sectors of the Southern Ocean, including the Weddell Sea (WS), Bellingshausen Sea (BS), Amundsen Sea (AS), Ross Sea (RS), and the Indian and western Pacific Ocean (IndWPac). The linear trends of the NLSIE are analyzed for each sector for the past 100–200 years and found to be −0.08°, −0.17°, +0.07°, +0.02°, and −0.03° per decade (≥95% confidence level) for the WS, BS, AS, RS, and IndWPac, respectively. For the entire Antarctic, our composite NLSIE shows a decreasing trend (−0.03° per decade, 99% confidence level) during the 20th century, with a rapid decline in the mid-1950s. It was not until the early 1980s that the observed increasing trend occurred. A comparison with major climate indices shows that the long-term linear trends in all five sectors are largely dominated by the changes in the Southern Annular Mode (SAM). The multi-decadal variability in WS, BS, and AS is dominated by the Interdecadal Pacific Oscillation, whereas that in the IndWPac and RS is dominated by the SAM.

The effects of spatiotemporal scale on commercial fishery abundance index suitability

Abstract With consideration of sophisticated modern commercial fisheries, the commonly used metric catch per unit effort (CPUE) may not be a reasonable proxy for generating abundance indices (AIs) for all species. Presumably, spatiotemporal scale is a critical factor that affects the accuracy of local/aggregated AIs derived from spatial modelling approaches, thus it is necessary to evaluate how scale affects scientific estimates of abundance. We explored three commonly utilized AI proxies, including aggregated catch (CatchAI), aggregated effort (EffortAI), and CPUEAI from the perspective of accuracy and spatial representational ability using a neural network (NN) model at different spatiotemporal scales. As a case example, we grouped the Chinese fleet's Northwest Pacific neon flying squid (Ommastrephes bartramii) fishery dataset (2009–2018) at four spatial scales (0.25° × 0.25°, 0.5° × 0.5°, 1° × 1°, 2° × 2°) to construct monthly and annual resolution models. The results showed that for both simulated and real datasets, AIs based on catch data had better accuracy, consistency, and spatial representational ability compared to CPUE and effort-dependent AI models at all spatial scales. Relative to the finest spatial scale, only results from the model with 0.5° × 0.5° resolution preserved enough distributional detail to reflect the known migration route for O. bartramii. Model results exhibited large variation dependent on spatial scale, particularly amongst CPUEAI scenarios. We suggest that scale comparisons among potential proxies should be conducted prior to AIs being used for applications such as population trends in stock assessment.

Constraining two climate field reconstruction methodologies over the North Atlantic realm using pseudo-proxy experiments

This study presents pseudo-proxy experiments to quantify the reconstruction skill of two climate field reconstruction methodologies for a marine proxy network subject to age uncertainties. The BARCAST methodology (Bayesian Algorithm for Reconstructing Climate Anomalies in Space and Time) is tested for sea surface temperature (SST) reconstruction for the first time over the northern North Atlantic region, and compared with a classic analogue reconstruction methodology. The reconstruction experiments are performed at annual and decadal resolution. We implement chronological uncertainties inherent to marine proxies as a novelty, using a simulated age-model ensemble covering the past millennium. Our experiments comprise different scenarios for the input data network, with the noise levels added to the target variable extending from ideal to realistic. Results show that both methodologies are able to reconstruct the Summer mean SST skillfully when the proxy network is considered absolutely dated, but the skill of the analogue method is superior to BARCAST. Only the analogue method provides skillful correlations with the true target variable in the case of a realistic noisy and age-uncertain proxy network. The spatiotemporal properties of the input target data are partly contrasting with the BARCAST model formulations, resulting in an inferior reconstruction ensemble that is similar to a white-noise stochastic process in time. The analogue method is also successful in reconstructing decadal temperatures, while BARCAST fails. The results contribute to constraining uncertainties in CFR for ocean dynamics which are highly important for climate across the globe.

A Fused Radar–Optical Approach for Mapping Wetlands and Deepwaters of the Mid–Atlantic and Gulf Coast Regions of the United States

Tidal wetlands are critically important ecosystems that provide ecosystem services including carbon sequestration, storm surge mitigation, water filtration, and wildlife habitat provision while supporting high levels of biodiversity. Despite their importance, monitoring these systems over large scales remains challenging due to difficulties in obtaining extensive up-to-date ground surveys and the need for high spatial and temporal resolution satellite imagery for effective space-borne monitoring. In this study, we developed methodologies to advance the monitoring of tidal marshes and adjacent deepwaters in the Mid-Atlantic and Gulf Coast United States. We combined Sentinel-1 SAR and Landsat 8 optical imagery to classify marshes and open water in both regions, with user’s and producer’s accuracies exceeding 89%. This methodology enables the assessment of marsh loss through conversion to open water at an annual resolution. We used time-series Sentinel-1 imagery to classify persistent and non-persistent marsh vegetation with greater than 93% accuracy. Non-persistent marsh vegetation serves as an indicator of salinity regimes in tidal wetlands. Additionally, we mapped two invasive species: wetlands invasive Phragmites australis (common reed) with greater than 80% accuracy and deepwater invasive Trapa natans (water chestnut) with greater than 96% accuracy. These results have important implications for improved monitoring and management of coastal wetlands ecosystems.

Reduced Temperature Sensitivity of Maximum Latewood Density Formation in High-Elevation Corsican Pines under Recent Warming

Maximum latewood density (MXD) measurements from long-lived Black pines (Pinus nigra spp. laricio) growing at the upper treeline in Corsica are one of the few archives to reconstruct southern European summer temperatures at annual resolution back into medieval times. Here, we present a compilation of five MXD chronologies from Corsican pines that contain high-to-low frequency variability between 1168 and 2016 CE and correlate significantly (p < 0.01) with the instrumental April–July and September–October mean temperatures from 1901 to 1980 CE (r = 0.52−0.64). The growth–climate correlations, however, dropped to −0.13 to 0.02 afterward, and scaling the MXD data resulted in a divergence of >1.5 °C between the colder reconstructed and warmer measured temperatures in the early-21st century. Our findings suggest a warming-induced shift from initially temperature-controlled to drought-prone MXD formation, and therefore question the suitability of using Corsican pine MXD data for climate reconstruction.

Dendroclimatology of teak indicates prevailing climatic conditions of tropical moist forests in India

Among all proxy archives, tree rings are highly promising indicator of ecological and environmental processes due to their high climatic sensitivity, better annual resolution, and large spatial coverage. Seasonal importance of soil moisture dynamics and impact of drought events on tree growth development and carbon sequestration potential in tropical moist forests was assessed using the teak tree ring width index and instrumental climate data from Aizawl, Mizoram. Present analysis suggests that soil moisture during months of the early growing season with low precipitation is crucial for determining the growth of teak trees in the Northeast region of India. Results of the present study reflected the impact of remote atmospheric climate regulation modes such as El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Sea surface temperature (SST) and Southern Oscillation Index (SOI) on site climate. Results indicate that the increasing moisture stresses in the region may cause the survival risk for the other forest vegetation having low adaptability to climate change stresses with the inability to make niche shifts. Increasing the number of tree ring studies linked with eco-physiological parameters of tree growth is recommended to better visualize the level of stresses on the trees in the moist tropical forests. This information will be useful in developing better management plans for biodiversity conservation in the tropical region.

Role of the Summer Monsoon Variability in the Collapse of the Ming Dynasty: Evidences From Speleothem Records

AbstractClimatic changes have played an important role in societal reorganizations. Particularly, the late 16th and early 17th century coincided with severely cold condition, extremely weak summer monsoon and widespread population decline in China. Here we present new speleothem oxygen isotope records across North and South China, which in concert with historical documents, allow us to characterize the “Late Ming Weak Monsoon Periods” (LMWMP) at an unprecedented annual temporal resolution. Our analysis suggests that as a weak summer monsoon event not seen for nearly 500 years in China, the LMWMP spatiotemporally coincided with the late Ming Dynasty peasant uprising (1627–1658 CE), and thus the transition from Ming to Qing Dynasty. This suggests a plausible role of climate change in shaping the important chapters of the Chinese history. In addition, both speleothem and historical documents reveal that the LMWMP appears to be a north to south time‐transgressive event on decadal‐timescale.