Pollen records from fluvial deposits in The Netherlands have traditionally been used to establish... more Pollen records from fluvial deposits in The Netherlands have traditionally been used to establish continental stages for the Neogene in NW Europe. These stages are still widely used across Europe for stratigraphic correlations and palaeoclimatic studies. Despite their extensive use, the validity of this continental correlation scheme for the Plio-and Pleistocene has never been tested in the area where they were originally proposed: the Roer Valley Graben (RVG). The fluvial and deltaic depositional setting in this area is controlled by a complex pattern of tectonic and climatic processes, which strongly complicates the definition of stages and sub-stages of regional or supra-regional significance.
Understanding relations between climate and pollen production is important for several societal a... more Understanding relations between climate and pollen production is important for several societal and ecological challenges, importantly pollen forecasting for pollinosis treatment, forensic studies, global change biology, and high-resolution palaeoecological studies of past vegetation and climate fluctuations. For these purposes, we investigate the role of climate variables on annual-scale variations in pollen influx, test the regional consistency of observed patterns, and evaluate the potential to reconstruct high-frequency signals from sediment archives. A 43-year pollen-trap record from the Netherlands is used to investigate relations between annual pollen influx, climate variables (monthly and seasonal temperature and precipitation values), and the North Atlantic Oscillation climate index. Spearman rank correlation analysis shows that specifically in Alnus, Betula, Corylus, Fraxinus, Quercus and Plantago both temperature in the year prior to (T -1 ), as well as in the growing season (T), are highly significant factors (T April r s between 0.30 [P,0.05[ and 0.58 [P,0.0001]; T Juli-1 rs between 0.32 [P,0.05[ and 0.56 [P,0.0001]) in the annual pollen influx of wind-pollinated plants. Total annual pollen prediction models based on multiple climate variables yield R 2 between 0.38 and 0.62 (P,0.0001). The effect of precipitation is minimal. A second trapping station in the SE Netherlands, shows consistent trends and annual variability, suggesting the climate factors are regionally relevant. Summer temperature is thought to influence the formation of reproductive structures, while temperature during the flowering season influences pollen release. This study provides a first predictive model for seasonal pollen forecasting, and also aides forensic studies. Furthermore, variations in pollen accumulation rates from a sub-fossil peat deposit are comparable with the pollen trap data. This suggests that high frequency variability pollen records from natural archives reflect annual past climate variability, and can be used in palaeoecological and -climatological studies to bridge between population-and species-scale responses to climate forcing. Citation: Donders TH, Hagemans K, Dekker SC, de Weger LA, de Klerk P, et al. (2014) Region-Specific Sensitivity of Anemophilous Pollen Deposition to Temperature and Precipitation. PLoS ONE 9(8): e104774.
A review of Holocene climate patterns in eastern Australia is presented on the basis of a series ... more A review of Holocene climate patterns in eastern Australia is presented on the basis of a series of high-resolution pollen records across a north-to-south transect. Previously published radiocarbon data are calibrated into calendar years and fitted with an age-depth model. The resulting chronologies are used to compare past environmental changes and describe patterns of climate change on a calendar-age scale. Based on the present-day Australian climate patterns and impact of the El Nin˜o-Southern Oscillation (ENSO), the palynological data are interpreted and the prevalent climate mode throughout the Holocene reconstructed. Results show that early Holocene changes are strongly divergent and asynchronous between sites, while middle to late Holocene conditions are characterized by more arid and variable conditions and greater coupling between northern and southern sites, which is in agreement with increasing influence of ENSO. r
Climate model studies have shown a gradual insolation-forced intensification of the El Nin˜o-Sout... more Climate model studies have shown a gradual insolation-forced intensification of the El Nin˜o-Southern Oscillation (ENSO) during the Holocene. Proxy records of past climate variability provide important test cases for such model simulations, and are needed to determine the exact mechanisms and dynamics of the ENSO system. We provide an integrated overview of marine and terrestrial paleoclimatic proxy data relevant for detecting ENSO variability. We reconstruct spatial climate patterns during two time-slices, 6-5 and 4.5-3.5 ka cal BP, to examine the mid-Holocene intensification of ENSO. The proxy data consistently indicate that a state change occurred at 5 ka cal BP towards active ENSO cyclicity in the equatorial Pacific. Furthermore, from around 3 ka cal BP the ENSOteleconnected regions are characterized by an increased impact of ENSO, comparable to the present-day high-amplitude fluctuations of ENSO. Model studies have thus far explained the late-Holocene intensification of ENSO by insolation-forced Pacific trade wind reduction during summer. Our review shows that this single mechanism cannot completely explain the observed Holocene changes. An additional mechanism is proposed, involving increased Indo-Pacific Warm Pool (IPWP) heat charging, which is a possible explanation for the late-Holocene increase in ENSO amplitude. r
An accurately dated peat profile from a mixed cypress swamp in the Fakahatchee Strand Preserve St... more An accurately dated peat profile from a mixed cypress swamp in the Fakahatchee Strand Preserve State Park (FSPSP, Florida, USA) has been examined for pollen and spores. The near-annual resolved pollen record shows a gradual shift from a wet to a relatively dry assemblage during the past 100 years. Timing of drainage activities in the region is accurately reflected by the onset and duration of vegetation change in the swamp. The reconstructed vegetation record has been statistically related to pollen assemblages from surface sediment samples. The response range of the FSPSP wetland to environmental perturbations could thus be determined and this allows better understanding of naturally occurring vegetation changes. In addition, the human impact on Florida wetlands becomes increasingly apparent. Superimposed high-frequency variation in the record suggests a positive correlation between winter-precipitation and pollen productivity of the dominant tree taxa. However, further high-resolution analysis is needed to confirm this relation. The response range of the FSPSP wetland to environmental perturbations on both annual-and decadalscales documented in this study allows recognition and quantification of natural hydrological changes in older deposits from southwest Florida. The strong link between local hydrology and the El Niño Southern Oscillation makes the palynological record from FSPSP highly relevant for studying past El Niño-variability.
Proceedings of the National Academy of Sciences, 2005
High resolution pollen analysis of mid-to late-Holocene peat deposits from southwest Florida reve... more High resolution pollen analysis of mid-to late-Holocene peat deposits from southwest Florida reveals a stepwise increase in wetland vegetation that points to an increased precipitationdriven fresh water flow during the past 5,000 years. The tight coupling between winter precipitation patterns in Florida and the strength of the El Niñ o-Southern Oscillation (ENSO) strongly suggests that the paleo-hydrology record reflects changes in ENSO intensity. A terrestrial subtropical record outside the Indo Pacific Warm Pool both documents ecosystem response to the known onset of modern-day ENSO periodicities, between Ϸ7,000 and 5,000 years B.P., and subsequent ENSO intensification after 3,500 years B.P. The observed increases in ''wetness'' are sustained by a gradual rise in relative sea level that prevents a return to drier vegetation through natural succession.
The dune system of Fraser Island in subtropical Queensland, Australia, contains numerous perched ... more The dune system of Fraser Island in subtropical Queensland, Australia, contains numerous perched lakes with organic-rich sediments. These lakes are located in the subtropics and their water levels are strongly influenced by precipitation. The lakes act as natural rainfall ...
Several episodes of abrupt and transient warming, each lasting between 50,000 and 200,000 years, ... more Several episodes of abrupt and transient warming, each lasting between 50,000 and 200,000 years, punctuated the long-term warming during the Late Palaeocene and Early Eocene (58 to 51 Myr ago) epochs 1,2 . These hyperthermal events, such as the Eocene Thermal Maximum 2 (EMT2) that took place about 53.5 Myr ago 2 , are associated with rapid increases in atmospheric CO 2 content. However, the impacts of most events are documented only locally 3,4 . Here we show, on the basis of estimates from the TEX 86 proxy, that sea surface temperatures rose by 3-5 • C in the Arctic Ocean during the EMT2. Dinoflagellate fossils demonstrate a concomitant freshening and eutrophication of surface waters, which resulted in euxinia in the photic zone. The presence of palm pollen implies 5 that coldest month mean temperatures over the Arctic land masses were no less than 8 • C, in contradiction of model simulations that suggest hyperthermal winter temperatures were below freezing 6 . In light of our reconstructed temperature and hydrologic trends, we conclude that the temperature and hydrographic responses to abruptly increased atmospheric CO 2 concentrations were similar for the ETM2 and the better-described Palaeocene-Eocene Thermal Maximum 7,8 , 55.5 Myr ago.
A 400-year sediment record from an 18 m deep scour hole lake (Haarsteegse Wiel) near the Meuse Ri... more A 400-year sediment record from an 18 m deep scour hole lake (Haarsteegse Wiel) near the Meuse River in the Netherlands was investigated for past changes in water quality, flooding frequency and landscape change using geophysical, geochemical and micropaleontological information. The results are highly significant for determining long-term trends of water quality, the impact of atmospheric (as SCP, spheroidal carbonaceous particles) and industrial (chromium) pollution on the terrestrial and aquatic flora, and the impact of river floods. The studied sediment record was dated by combining 137 Cs activities, biostratigraphical ages, micro-tephra layers, and historically documented floods indicated by the magnetic susceptibility. The oldest flooding event is indicated at AD 1610 when the lake was Electronic supplementary material The online version of this article (
International Journal of Greenhouse Gas Control, 2013
Monitoring the surface composition of CO 2 derived from subsurface reservoirs is an important par... more Monitoring the surface composition of CO 2 derived from subsurface reservoirs is an important part of the carbon capture and storage (CCS) chain. Most approaches use geochemical or geophysical instrumental approaches but these have the drawback that no long-term time series are available, which depend on a predefined monitoring location. We test a flexible approach using natural archives based on the measurement of radiogenic 14 C concentrations in tree rings to detect geogenic CO 2 fluxes derived from natural springs in the Latera Caldera, central Italy. The approach can be used as a preliminary check to evaluate natural CO 2 leaks from sites designated for CO 2 storage, as well as evaluating the extent of leakage in an unforeseen area. An extensive database of soil gas composition and fluxes is available for that site, permitting direct comparison of the tree ring isotopic composition and point sources of CO 2 from the subsurface against the mean atmospheric standard. We sampled oak trees (Quercus cerris and Quercus pubescens) directly at the CO 2 source (ON), and at short (50 m, NEAR), intermediate (500 m, FAR) and long distances (∼3000 m, CONTROL) from CO 2 , sources, and measured the radioactive 14 C concentration in tree rings at ∼10 year intervals from 2012 back to 1976. To accurately date the tree rings we constructed a tree-ring chronology using standard dendrochronological methods. We tested whether variation in 14 C concentration in tree rings and ring-width are related to distance of trees from CO 2 source, as well as climate factors, i.e. precipitation and temperature. Results show that local point sources of CO 2 at the location where the tree grows are effectively recorded by the 14 C concentration in the cellulose of this tree. The fossil CO 2 signal is sharply delineated since already at short distance from the source (∼50 m, NEAR) the 14 C incorporation is at the detection limit of the tested approach. Tree-ring width of the oaks at Caldera Latera is mainly limited by the amount of precipitation during the growing season, from March to October, while distance to the CO 2 point source has no detectable effect on radial growth, likely due to the continuous presence of the enhanced CO 2 flux to which the trees adapt their physiology from germination. While the approach is promising and permits data collection at any forested site, a more detailed sampling transect between 0 and 50 m from a point source of CO 2 is needed to determine the exact detection limit of the signal in the 14 C concentration of the tree ring cellulose.
The presence of high abundances of the freshwater fern Azolla in the early Middle Eocene central ... more The presence of high abundances of the freshwater fern Azolla in the early Middle Eocene central Arctic Ocean sediments recovered from the Lomonosov Ridge during IODP Expedition 302, have been related to the presence of a substantial freshwater cap. Azolla massulae, belonging to the newly described Eocene species Azolla arctica Collinson et al., have been found over at least a ∼4 m-thick interval. There are strong indications that Azolla has bloomed and reproduced in situ in the Arctic Ocean for several hundreds of thousands of years. Possible causes for the sudden demise of Azolla at ∼48.1 Ma include salinity changes due to evolving oceanic connections or sea-level change.
Recent trends in the trophic conditions of the north-western Adriatic Sea have been evaluated usi... more Recent trends in the trophic conditions of the north-western Adriatic Sea have been evaluated using organic-walled dinoflagellate cysts (dinocysts), pollen and spores. Palynological analyses performed on a sediment core covering the period AD 1830e1990 have revealed a progressive increase in eutrophication beginning in the 20th century. The first signal of a change seems to occur earlier in the terrestrial ecosystem and later in the marine realm. Pollen data indicate that the source of enhanced nutrient loading to the North Adriatic Sea, which partly resulted from increased wetland reclamation and forest clearance, began at about AD 1910. The clear shift in the relative abundance of the dinocyst Lingulodinium machaerophorum at AD 1930 suggests an increase in eutrophication. Dinocyst assemblages point to stressful conditions from AD 1960, reaching a maximum at about AD 1978. Subsequently eutrophication levels decrease, although dinocyst diversity suggests that the ecosystem has not completely recovered.
A suite of organic geochemical, micropaleontological and palynological proxies was applied to sed... more A suite of organic geochemical, micropaleontological and palynological proxies was applied to sediments from Southwest Florida, to study the Holocene environmental changes associated with sea-level rise. Sediments were recovered from Hillsborough Bay, part of Tampa Bay, and studied using biomarkers, pollen, organic-walled dinoflagellate cysts and diatoms. Analyses show that the site flooded around 7.5 ka as a consequence of Holocene transgression, progressively turning a fresh/brackish marl-marsh into a shallow, restricted marine environment. Immediately after the marine transgression started, limited water circulation and high amounts of runoff caused stratification of the water column. A shift in dinocysts and diatom assemblages to more marine species, increasing concentrations of marine biomarkers and a shift in the Diol Index indicate increasing salinity between 7.5 ka and the present, which is likely a consequence of progressing sea-level rise. Reconstructed sea surface temperatures for the past 4 kyrs are between 25 and 26 C, and indicate stable temperatures during the Late Holocene. A sharp increase in sedimentation rate in the top w50 cm of the core is attributed to human impact. The results are in agreement with parallel studies from the area, but this study further refines the environmental reconstructions having the advantage of simultaneously investigating changes in the terrestrial and marine environment.
Pollen records from fluvial deposits in The Netherlands have traditionally been used to establish... more Pollen records from fluvial deposits in The Netherlands have traditionally been used to establish continental stages for the Neogene in NW Europe. These stages are still widely used across Europe for stratigraphic correlations and palaeoclimatic studies. Despite their extensive use, the validity of this continental correlation scheme for the Plio-and Pleistocene has never been tested in the area where they were originally proposed: the Roer Valley Graben (RVG). The fluvial and deltaic depositional setting in this area is controlled by a complex pattern of tectonic and climatic processes, which strongly complicates the definition of stages and sub-stages of regional or supra-regional significance.
Recurrent phases of increased pine at Lake Tulane, Florida have previously been related to strong... more Recurrent phases of increased pine at Lake Tulane, Florida have previously been related to strong stadials terminated by so-called Heinrich events. The climatic significance of these pine phases has been interpreted in different ways. Using a pollen-climate inference model, we quantified the climate changes and consistently found that mean summer precipitation (P JJA ) increased (0.5-0.9 mm/day) and mean November temperature increased (2.0-3.0°C) during pine phases coeval with Heinrich events and the Younger Dryas. Marine sea surface temperature records indicate that potential sources for these moisture and heat anomalies are in the Gulf of Mexico and the western tropical Atlantic. We explain this low latitude warming by an increased Loop Current facilitated by persistence of the Atlantic Warm Pool during summer. This hypothesis is supported by a climate model sensitivity analysis. A positive heat anomaly in the Gulf of Mexico and equatorial Atlantic best approximates the polleninferred climate reconstructions from Lake Tulane during the (stadials around) Heinrich events and the Younger Dryas.
Sub-fossil sections from a Florida wetland were accelerator mass spectrometry (AMS) dated and the... more Sub-fossil sections from a Florida wetland were accelerator mass spectrometry (AMS) dated and the sedimentological conditions were determined. ¹⁴C data were calibrated using a combined wiggle-match and ¹⁴C bomb-pulse approach. Repeatable results were obtained providing accurate peat chronologies for the last 130 calendar yr. Assessment of the different errors involved led to age models with 3–5 yr precision. This allows direct calibration of paleoenvironmental proxies with meteorological data. The time frame in which ¹⁴C dating is commonly applied can possibly be extended to include the 20th century.
Pollen records from fluvial deposits in The Netherlands have traditionally been used to establish... more Pollen records from fluvial deposits in The Netherlands have traditionally been used to establish continental stages for the Neogene in NW Europe. These stages are still widely used across Europe for stratigraphic correlations and palaeoclimatic studies. Despite their extensive use, the validity of this continental correlation scheme for the Plio-and Pleistocene has never been tested in the area where they were originally proposed: the Roer Valley Graben (RVG). The fluvial and deltaic depositional setting in this area is controlled by a complex pattern of tectonic and climatic processes, which strongly complicates the definition of stages and sub-stages of regional or supra-regional significance.
Understanding relations between climate and pollen production is important for several societal a... more Understanding relations between climate and pollen production is important for several societal and ecological challenges, importantly pollen forecasting for pollinosis treatment, forensic studies, global change biology, and high-resolution palaeoecological studies of past vegetation and climate fluctuations. For these purposes, we investigate the role of climate variables on annual-scale variations in pollen influx, test the regional consistency of observed patterns, and evaluate the potential to reconstruct high-frequency signals from sediment archives. A 43-year pollen-trap record from the Netherlands is used to investigate relations between annual pollen influx, climate variables (monthly and seasonal temperature and precipitation values), and the North Atlantic Oscillation climate index. Spearman rank correlation analysis shows that specifically in Alnus, Betula, Corylus, Fraxinus, Quercus and Plantago both temperature in the year prior to (T -1 ), as well as in the growing season (T), are highly significant factors (T April r s between 0.30 [P,0.05[ and 0.58 [P,0.0001]; T Juli-1 rs between 0.32 [P,0.05[ and 0.56 [P,0.0001]) in the annual pollen influx of wind-pollinated plants. Total annual pollen prediction models based on multiple climate variables yield R 2 between 0.38 and 0.62 (P,0.0001). The effect of precipitation is minimal. A second trapping station in the SE Netherlands, shows consistent trends and annual variability, suggesting the climate factors are regionally relevant. Summer temperature is thought to influence the formation of reproductive structures, while temperature during the flowering season influences pollen release. This study provides a first predictive model for seasonal pollen forecasting, and also aides forensic studies. Furthermore, variations in pollen accumulation rates from a sub-fossil peat deposit are comparable with the pollen trap data. This suggests that high frequency variability pollen records from natural archives reflect annual past climate variability, and can be used in palaeoecological and -climatological studies to bridge between population-and species-scale responses to climate forcing. Citation: Donders TH, Hagemans K, Dekker SC, de Weger LA, de Klerk P, et al. (2014) Region-Specific Sensitivity of Anemophilous Pollen Deposition to Temperature and Precipitation. PLoS ONE 9(8): e104774.
A review of Holocene climate patterns in eastern Australia is presented on the basis of a series ... more A review of Holocene climate patterns in eastern Australia is presented on the basis of a series of high-resolution pollen records across a north-to-south transect. Previously published radiocarbon data are calibrated into calendar years and fitted with an age-depth model. The resulting chronologies are used to compare past environmental changes and describe patterns of climate change on a calendar-age scale. Based on the present-day Australian climate patterns and impact of the El Nin˜o-Southern Oscillation (ENSO), the palynological data are interpreted and the prevalent climate mode throughout the Holocene reconstructed. Results show that early Holocene changes are strongly divergent and asynchronous between sites, while middle to late Holocene conditions are characterized by more arid and variable conditions and greater coupling between northern and southern sites, which is in agreement with increasing influence of ENSO. r
Climate model studies have shown a gradual insolation-forced intensification of the El Nin˜o-Sout... more Climate model studies have shown a gradual insolation-forced intensification of the El Nin˜o-Southern Oscillation (ENSO) during the Holocene. Proxy records of past climate variability provide important test cases for such model simulations, and are needed to determine the exact mechanisms and dynamics of the ENSO system. We provide an integrated overview of marine and terrestrial paleoclimatic proxy data relevant for detecting ENSO variability. We reconstruct spatial climate patterns during two time-slices, 6-5 and 4.5-3.5 ka cal BP, to examine the mid-Holocene intensification of ENSO. The proxy data consistently indicate that a state change occurred at 5 ka cal BP towards active ENSO cyclicity in the equatorial Pacific. Furthermore, from around 3 ka cal BP the ENSOteleconnected regions are characterized by an increased impact of ENSO, comparable to the present-day high-amplitude fluctuations of ENSO. Model studies have thus far explained the late-Holocene intensification of ENSO by insolation-forced Pacific trade wind reduction during summer. Our review shows that this single mechanism cannot completely explain the observed Holocene changes. An additional mechanism is proposed, involving increased Indo-Pacific Warm Pool (IPWP) heat charging, which is a possible explanation for the late-Holocene increase in ENSO amplitude. r
An accurately dated peat profile from a mixed cypress swamp in the Fakahatchee Strand Preserve St... more An accurately dated peat profile from a mixed cypress swamp in the Fakahatchee Strand Preserve State Park (FSPSP, Florida, USA) has been examined for pollen and spores. The near-annual resolved pollen record shows a gradual shift from a wet to a relatively dry assemblage during the past 100 years. Timing of drainage activities in the region is accurately reflected by the onset and duration of vegetation change in the swamp. The reconstructed vegetation record has been statistically related to pollen assemblages from surface sediment samples. The response range of the FSPSP wetland to environmental perturbations could thus be determined and this allows better understanding of naturally occurring vegetation changes. In addition, the human impact on Florida wetlands becomes increasingly apparent. Superimposed high-frequency variation in the record suggests a positive correlation between winter-precipitation and pollen productivity of the dominant tree taxa. However, further high-resolution analysis is needed to confirm this relation. The response range of the FSPSP wetland to environmental perturbations on both annual-and decadalscales documented in this study allows recognition and quantification of natural hydrological changes in older deposits from southwest Florida. The strong link between local hydrology and the El Niño Southern Oscillation makes the palynological record from FSPSP highly relevant for studying past El Niño-variability.
Proceedings of the National Academy of Sciences, 2005
High resolution pollen analysis of mid-to late-Holocene peat deposits from southwest Florida reve... more High resolution pollen analysis of mid-to late-Holocene peat deposits from southwest Florida reveals a stepwise increase in wetland vegetation that points to an increased precipitationdriven fresh water flow during the past 5,000 years. The tight coupling between winter precipitation patterns in Florida and the strength of the El Niñ o-Southern Oscillation (ENSO) strongly suggests that the paleo-hydrology record reflects changes in ENSO intensity. A terrestrial subtropical record outside the Indo Pacific Warm Pool both documents ecosystem response to the known onset of modern-day ENSO periodicities, between Ϸ7,000 and 5,000 years B.P., and subsequent ENSO intensification after 3,500 years B.P. The observed increases in ''wetness'' are sustained by a gradual rise in relative sea level that prevents a return to drier vegetation through natural succession.
The dune system of Fraser Island in subtropical Queensland, Australia, contains numerous perched ... more The dune system of Fraser Island in subtropical Queensland, Australia, contains numerous perched lakes with organic-rich sediments. These lakes are located in the subtropics and their water levels are strongly influenced by precipitation. The lakes act as natural rainfall ...
Several episodes of abrupt and transient warming, each lasting between 50,000 and 200,000 years, ... more Several episodes of abrupt and transient warming, each lasting between 50,000 and 200,000 years, punctuated the long-term warming during the Late Palaeocene and Early Eocene (58 to 51 Myr ago) epochs 1,2 . These hyperthermal events, such as the Eocene Thermal Maximum 2 (EMT2) that took place about 53.5 Myr ago 2 , are associated with rapid increases in atmospheric CO 2 content. However, the impacts of most events are documented only locally 3,4 . Here we show, on the basis of estimates from the TEX 86 proxy, that sea surface temperatures rose by 3-5 • C in the Arctic Ocean during the EMT2. Dinoflagellate fossils demonstrate a concomitant freshening and eutrophication of surface waters, which resulted in euxinia in the photic zone. The presence of palm pollen implies 5 that coldest month mean temperatures over the Arctic land masses were no less than 8 • C, in contradiction of model simulations that suggest hyperthermal winter temperatures were below freezing 6 . In light of our reconstructed temperature and hydrologic trends, we conclude that the temperature and hydrographic responses to abruptly increased atmospheric CO 2 concentrations were similar for the ETM2 and the better-described Palaeocene-Eocene Thermal Maximum 7,8 , 55.5 Myr ago.
A 400-year sediment record from an 18 m deep scour hole lake (Haarsteegse Wiel) near the Meuse Ri... more A 400-year sediment record from an 18 m deep scour hole lake (Haarsteegse Wiel) near the Meuse River in the Netherlands was investigated for past changes in water quality, flooding frequency and landscape change using geophysical, geochemical and micropaleontological information. The results are highly significant for determining long-term trends of water quality, the impact of atmospheric (as SCP, spheroidal carbonaceous particles) and industrial (chromium) pollution on the terrestrial and aquatic flora, and the impact of river floods. The studied sediment record was dated by combining 137 Cs activities, biostratigraphical ages, micro-tephra layers, and historically documented floods indicated by the magnetic susceptibility. The oldest flooding event is indicated at AD 1610 when the lake was Electronic supplementary material The online version of this article (
International Journal of Greenhouse Gas Control, 2013
Monitoring the surface composition of CO 2 derived from subsurface reservoirs is an important par... more Monitoring the surface composition of CO 2 derived from subsurface reservoirs is an important part of the carbon capture and storage (CCS) chain. Most approaches use geochemical or geophysical instrumental approaches but these have the drawback that no long-term time series are available, which depend on a predefined monitoring location. We test a flexible approach using natural archives based on the measurement of radiogenic 14 C concentrations in tree rings to detect geogenic CO 2 fluxes derived from natural springs in the Latera Caldera, central Italy. The approach can be used as a preliminary check to evaluate natural CO 2 leaks from sites designated for CO 2 storage, as well as evaluating the extent of leakage in an unforeseen area. An extensive database of soil gas composition and fluxes is available for that site, permitting direct comparison of the tree ring isotopic composition and point sources of CO 2 from the subsurface against the mean atmospheric standard. We sampled oak trees (Quercus cerris and Quercus pubescens) directly at the CO 2 source (ON), and at short (50 m, NEAR), intermediate (500 m, FAR) and long distances (∼3000 m, CONTROL) from CO 2 , sources, and measured the radioactive 14 C concentration in tree rings at ∼10 year intervals from 2012 back to 1976. To accurately date the tree rings we constructed a tree-ring chronology using standard dendrochronological methods. We tested whether variation in 14 C concentration in tree rings and ring-width are related to distance of trees from CO 2 source, as well as climate factors, i.e. precipitation and temperature. Results show that local point sources of CO 2 at the location where the tree grows are effectively recorded by the 14 C concentration in the cellulose of this tree. The fossil CO 2 signal is sharply delineated since already at short distance from the source (∼50 m, NEAR) the 14 C incorporation is at the detection limit of the tested approach. Tree-ring width of the oaks at Caldera Latera is mainly limited by the amount of precipitation during the growing season, from March to October, while distance to the CO 2 point source has no detectable effect on radial growth, likely due to the continuous presence of the enhanced CO 2 flux to which the trees adapt their physiology from germination. While the approach is promising and permits data collection at any forested site, a more detailed sampling transect between 0 and 50 m from a point source of CO 2 is needed to determine the exact detection limit of the signal in the 14 C concentration of the tree ring cellulose.
The presence of high abundances of the freshwater fern Azolla in the early Middle Eocene central ... more The presence of high abundances of the freshwater fern Azolla in the early Middle Eocene central Arctic Ocean sediments recovered from the Lomonosov Ridge during IODP Expedition 302, have been related to the presence of a substantial freshwater cap. Azolla massulae, belonging to the newly described Eocene species Azolla arctica Collinson et al., have been found over at least a ∼4 m-thick interval. There are strong indications that Azolla has bloomed and reproduced in situ in the Arctic Ocean for several hundreds of thousands of years. Possible causes for the sudden demise of Azolla at ∼48.1 Ma include salinity changes due to evolving oceanic connections or sea-level change.
Recent trends in the trophic conditions of the north-western Adriatic Sea have been evaluated usi... more Recent trends in the trophic conditions of the north-western Adriatic Sea have been evaluated using organic-walled dinoflagellate cysts (dinocysts), pollen and spores. Palynological analyses performed on a sediment core covering the period AD 1830e1990 have revealed a progressive increase in eutrophication beginning in the 20th century. The first signal of a change seems to occur earlier in the terrestrial ecosystem and later in the marine realm. Pollen data indicate that the source of enhanced nutrient loading to the North Adriatic Sea, which partly resulted from increased wetland reclamation and forest clearance, began at about AD 1910. The clear shift in the relative abundance of the dinocyst Lingulodinium machaerophorum at AD 1930 suggests an increase in eutrophication. Dinocyst assemblages point to stressful conditions from AD 1960, reaching a maximum at about AD 1978. Subsequently eutrophication levels decrease, although dinocyst diversity suggests that the ecosystem has not completely recovered.
A suite of organic geochemical, micropaleontological and palynological proxies was applied to sed... more A suite of organic geochemical, micropaleontological and palynological proxies was applied to sediments from Southwest Florida, to study the Holocene environmental changes associated with sea-level rise. Sediments were recovered from Hillsborough Bay, part of Tampa Bay, and studied using biomarkers, pollen, organic-walled dinoflagellate cysts and diatoms. Analyses show that the site flooded around 7.5 ka as a consequence of Holocene transgression, progressively turning a fresh/brackish marl-marsh into a shallow, restricted marine environment. Immediately after the marine transgression started, limited water circulation and high amounts of runoff caused stratification of the water column. A shift in dinocysts and diatom assemblages to more marine species, increasing concentrations of marine biomarkers and a shift in the Diol Index indicate increasing salinity between 7.5 ka and the present, which is likely a consequence of progressing sea-level rise. Reconstructed sea surface temperatures for the past 4 kyrs are between 25 and 26 C, and indicate stable temperatures during the Late Holocene. A sharp increase in sedimentation rate in the top w50 cm of the core is attributed to human impact. The results are in agreement with parallel studies from the area, but this study further refines the environmental reconstructions having the advantage of simultaneously investigating changes in the terrestrial and marine environment.
Pollen records from fluvial deposits in The Netherlands have traditionally been used to establish... more Pollen records from fluvial deposits in The Netherlands have traditionally been used to establish continental stages for the Neogene in NW Europe. These stages are still widely used across Europe for stratigraphic correlations and palaeoclimatic studies. Despite their extensive use, the validity of this continental correlation scheme for the Plio-and Pleistocene has never been tested in the area where they were originally proposed: the Roer Valley Graben (RVG). The fluvial and deltaic depositional setting in this area is controlled by a complex pattern of tectonic and climatic processes, which strongly complicates the definition of stages and sub-stages of regional or supra-regional significance.
Recurrent phases of increased pine at Lake Tulane, Florida have previously been related to strong... more Recurrent phases of increased pine at Lake Tulane, Florida have previously been related to strong stadials terminated by so-called Heinrich events. The climatic significance of these pine phases has been interpreted in different ways. Using a pollen-climate inference model, we quantified the climate changes and consistently found that mean summer precipitation (P JJA ) increased (0.5-0.9 mm/day) and mean November temperature increased (2.0-3.0°C) during pine phases coeval with Heinrich events and the Younger Dryas. Marine sea surface temperature records indicate that potential sources for these moisture and heat anomalies are in the Gulf of Mexico and the western tropical Atlantic. We explain this low latitude warming by an increased Loop Current facilitated by persistence of the Atlantic Warm Pool during summer. This hypothesis is supported by a climate model sensitivity analysis. A positive heat anomaly in the Gulf of Mexico and equatorial Atlantic best approximates the polleninferred climate reconstructions from Lake Tulane during the (stadials around) Heinrich events and the Younger Dryas.
Sub-fossil sections from a Florida wetland were accelerator mass spectrometry (AMS) dated and the... more Sub-fossil sections from a Florida wetland were accelerator mass spectrometry (AMS) dated and the sedimentological conditions were determined. ¹⁴C data were calibrated using a combined wiggle-match and ¹⁴C bomb-pulse approach. Repeatable results were obtained providing accurate peat chronologies for the last 130 calendar yr. Assessment of the different errors involved led to age models with 3–5 yr precision. This allows direct calibration of paleoenvironmental proxies with meteorological data. The time frame in which ¹⁴C dating is commonly applied can possibly be extended to include the 20th century.
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Papers by Timme Donders