ORCID Profile
0000-0001-9988-6638
Current Organisation
Universidad Técnica Federico Santa María Departamento de Física
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Publications
Lakes and trees as climate and environment archives: the TERENO Northeastern German Lowland Observatory
Publisher: Copernicus GmbH
Date: 15-09-2022
DOI: 10.5194/DEUQUASP-4-41-2022
Abstract: Abstract. Robust reconstruction of past climate and environmental change based on proxy data obtained from natural archives requires an in-depth understanding of the processes and mechanisms that form and determine these proxies. Here we present comprehensive long-term monitoring projects for seasonally laminated (varved) lake sediments and tree rings in the northern German lowlands. The two monitoring sites are located in the nature park Nossentiner/Schwinzer Heide (Tiefer See) and in the Müritz National Park (tree rings) and are an integral part of the Helmholtz TERrestrial ENvironmental Observatories (TERENO) infrastructure initiative. Both sites are located in the close vicinity of moraine deposits of the main ice advance of the Pomeranian phase of the Weichselian glaciation. This field guide provides an introduction to the local morphologies and landscapes as well as details of the monitoring concepts and some selected results.
European hydroclimate variability of the past 400 years based on tree-ring isotopes
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-14680
Abstract: In recent decades, Europe has experienced more frequent flood and drought events. However, little is known about the long-term, spatiotemporal hydroloclimatic changes across Europe. We show the first climate field reconstruction spanning the entire European continent based on tree-ring stable isotopes. A pronounced seasonal consistency in climate response across Europe leads to a unique, well-verified spatial field reconstruction of European summer hydroclimate back to 1600. We find distinct phases of European hydroclimate variability as possible fingerprints of solar activity (coinciding with the Maunder Minimum and the end of the Little Ice Age), pronounced decadal variability and a long-term drying trend from the mid 20th century. The recent European summer conditions are highly unusual in a multi-century context and unprecedented for large parts of central and western Europe.
Large scale climate signals of a European oxygen isotope network from tree-rings – predominantly caused by ENSO teleconnections?
Publisher: Copernicus GmbH
Date: 30-03-2020
DOI: 10.5194/CP-2020-39
Abstract: Abstract. We investigate the annual variability of δ18O tree ring records from sites distributed all over Europe covering the last 400 years. An Empirical Orthogonal Function (EOF) analysis reveals two distinct modes of variability on the basis of the existing δ18O tree ring records. The first mode of δ18O variability is associated with anomaly patterns of the El Niño-Southern Oscillation (ENSO) and reflects a multi-seasonal climatic signal. The ENSO signal is visible for the last 130 years, but is found weak during the period 1600 to 1850 suggesting that the relationship between ENSO and the European climate may not stable over time. The second mode of δ18O variability, which captures an out-of-phase variability between northwestern and southeastern European δ18O tree ring records, is related to a regional summer atmospheric circulation pattern revealing a pronounced centre over the North Sea. Locally, the δ18O anomalies associated with this mode show the same (opposite) sign with temperature (precipitation). We infer that the investigation of large-scale atmospheric circulation patterns and related teleconnections far beyond instrumental records can be done with oxygen isotopic signature derived from tree rings. However, the European δ18Ocel tree network needs to be consolidated and updated, as well as additional research on the stationarity of reconstructed climate signals and the stationarity of teleconnections is advisable.
Changes in El Niño – Southern Oscillation (ENSO) conditions during the Greenland Stadial 1 (GS-1) chronozone revealed by New Zealand tree-rings
Publisher: Elsevier BV
Date: 12-2016
Decadally Resolved Lateglacial Radiocarbon Evidence from New Zealand Kauri
Publisher: Cambridge University Press (CUP)
Date: 24-10-2016
DOI: 10.1017/RDC.2016.86
Abstract: The Last Glacial–Interglacial Transition (LGIT 15,000–11,000 cal BP) was characterized by complex spatiotemporal patterns of climate change, with numerous studies requiring accurate chronological control to decipher leads from lags in global paleoclimatic, paleoenvironmental, and archaeological records. However, close scrutiny of the few available tree-ring chronologies and radiocarbon-dated sequences composing the IntCal13 14 C calibration curve indicates significant weakness in 14 C calibration across key periods of the LGIT. Here, we present a decadally resolved atmospheric 14 C record derived from New Zealand kauri spanning the Lateglacial from ~13,100–11,365 cal BP. Two floating kauri 14 C time series, curve-matched to IntCal13, serve as a 14 C backbone through the Younger Dryas. The floating Northern Hemisphere (NH) 14 C data sets derived from the YD-B and Central European Lateglacial Master tree-ring series are matched against the new kauri data, forming a robust NH 14 C time series to ~14,200 cal BP. Our results show that IntCal13 is questionable from ~12,200–11,900 cal BP and the ~10,400 BP 14 C plateau is approximately 5 decades too short. The new kauri record and repositioned NH pine 14 C series offer a refinement of the international 14 C calibration curves IntCal13 and SHCal13, providing increased confidence in the correlation of global paleorecords.
Punctuated Shutdown of Atlantic Meridional Overturning Circulation during Greenland Stadial 1
Publisher: Springer Science and Business Media LLC
Date: 19-05-2016
DOI: 10.1038/SREP25902
Abstract: The Greenland Stadial 1 (GS-1 ~12.9 to 11.65 kyr cal BP) was a period of North Atlantic cooling, thought to have been initiated by North America fresh water runoff that caused a sustained reduction of North Atlantic Meridional Overturning Circulation (AMOC), resulting in an antiphase temperature response between the hemispheres (the ‘bipolar seesaw’). Here we exploit sub-fossil New Zealand kauri trees to report the first securely dated, decadally-resolved atmospheric radiocarbon ( 14 C) record spanning GS-1. By precisely aligning Southern and Northern Hemisphere tree-ring 14 C records with marine 14 C sequences we document two relatively short periods of AMOC collapse during the stadial, at ~12,920-12,640 cal BP and 12,050-11,900 cal BP. In addition, our data show that the interhemispheric atmospheric 14 C offset was close to zero prior to GS-1, before reaching ‘near-modern’ values at ~12,660 cal BP, consistent with synchronous recovery of overturning in both hemispheres and increased Southern Ocean ventilation. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but probably due to an equatorward migration of the Polar Front, reducing the advection of southwesterly air masses to high latitudes. Our findings suggest opposing hemispheric temperature trends were driven by atmospheric teleconnections, rather than AMOC changes.
Attitudes of healthcare providers towards family involvement and presence in adult critical care units in Saudi Arabia: a quantitative study.
Publisher: Wiley
Date: 20-12-2014
DOI: 10.1111/JOCN.12520
Abstract: To describe healthcare providers' attitudes to family involvement during routine care and family presence during resuscitation or other invasive procedures in adult intensive care units in Saudi Arabia. Previous research has shown that healthcare professionals have revealed a ersity of opinions on family involvement during routine care and family presence during resuscitation or other invasive procedures. Attitude assessment can provide an indication of staff acceptance or rejection of the practice and also help identify key potential barriers that will need to be addressed. It has also been evident that participation in the care has potential benefits for patients and families as well as healthcare providers. A quantitative descriptive design. A questionnaire was used with a convenience s le of 468 healthcare providers who were recruited from eight intensive care units. The analysis found that healthcare providers had positive attitudes towards family involvement during routine care, but negative attitudes towards family presence during resuscitation or other invasive procedures. Physicians expressed more opposition to the practice than did nurses and respiratory therapists. Staff indicated a need to develop written guidelines and policies, as well as educational programmes, to address this sensitive issue in clinical practice. Family is an important resource in patient care in the context of the critical care environment. Clinical barriers including resources, hospital policies and guidelines, staff and public education should be taken into account to facilitate family integration to the care model. The findings can help to develop policies and guidelines for safe implementation of the practice. They can also encourage those who design nursing and other medical curricula to place more emphasis on the role of the family especially in critical care settings.
Supplementary material to A past and present perspective on the European summer vapour pressure deficit
Publisher: Copernicus GmbH
Date: 08-06-2023
European tree-ring isotopes indicate unusual recent hydroclimate
Publisher: Springer Science and Business Media LLC
Date: 08-02-2023
DOI: 10.1038/S43247-022-00648-7
Abstract: In recent decades, Europe has experienced more frequent flood and drought events. However, little is known about the long-term, spatiotemporal hydroclimatic changes across Europe. Here we present a climate field reconstruction spanning the entire European continent based on tree-ring stable isotopes. A pronounced seasonal consistency in climate response across Europe leads to a unique, well-verified spatial field reconstruction of European summer hydroclimate back to AD 1600. We find three distinct phases of European hydroclimate variability as possible fingerprints of solar activity (coinciding with the Maunder Minimum and the end of the Little Ice Age) and pronounced decadal variability superimposed by a long-term drying trend from the mid-20th century. We show that the recent European summer drought (2015–2018) is highly unusual in a multi-century context and unprecedented for large parts of central and western Europe. The reconstruction provides further evidence of European summer droughts potentially being influenced by anthropogenic warming and draws attention to regional differences.
Large-scale climate signals of a European oxygen isotope network from tree rings
Publisher: Copernicus GmbH
Date: 07-05-2021
Abstract: Abstract. We investigate the climate signature of δ18O tree-ring records from sites distributed all over Europe covering the last 400 years. An empirical orthogonal function (EOF) analysis reveals two distinct modes of variability on the basis of the existing δ18O tree-ring records. The first mode is associated with anomaly patterns projecting onto the El Niño–Southern Oscillation (ENSO) and reflects a multi-seasonal climatic signal. The ENSO link is pronounced for the last 130 years, but it is found to be weak over the period from 1600 to 1850, suggesting that the relationship between ENSO and the European climate may not be stable over time. The second mode of δ18O variability, which captures a north–south dipole in the European δ18O tree-ring records, is related to a regional summer atmospheric circulation pattern, revealing a pronounced centre over the North Sea. Locally, the δ18O anomalies associated with this mode show the same (opposite) sign with temperature (precipitation). Based on the oxygen isotopic signature derived from tree rings, we argue that the prevailing large-scale atmospheric circulation patterns and the related teleconnections can be analysed beyond instrumental records.
Supplementary material to "A past, present and future perspective on the European summer vapour pressure deficit"
Publisher: Copernicus GmbH
Date: 09-02-2022
Subfossil trees suggest enhanced Mediterranean hydroclimate variability at the onset of the Younger Dryas
Publisher: Springer Science and Business Media LLC
Date: 18-09-2018
DOI: 10.1038/S41598-018-32251-2
Abstract: Nearly 13,000 years ago, the warming trend into the Holocene was sharply interrupted by a reversal to near glacial conditions. Climatic causes and ecological consequences of the Younger Dryas (YD) have been extensively studied, however proxy archives from the Mediterranean basin capturing this period are scarce and do not provide annual resolution. Here, we report a hydroclimatic reconstruction from stable isotopes (δ 18 O, δ 13 C) in subfossil pines from southern France. Growing before and during the transition period into the YD (12 900–12 600 cal BP), the trees provide an annually resolved, continuous sequence of atmospheric change. Isotopic signature of tree sourcewater (δ 18 O sw ) and estimates of relative air humidity were reconstructed as a proxy for variations in air mass origin and precipitation regime. We find a distinct increase in inter-annual variability of sourcewater isotopes (δ 18 O sw ), with three major downturn phases of increasing magnitude beginning at 12 740 cal BP. The observed variation most likely results from an lified intensity of North Atlantic (low δ 18 O sw ) versus Mediterranean (high δ 18 O sw ) precipitation. This marked pattern of climate variability is not seen in records from higher latitudes and is likely a consequence of atmospheric circulation oscillations at the margin of the southward moving polar front.
Minimum winter temperature reconstruction from average earlywood vessel area of European oak (Quercus robur) in N-Poland
Publisher: Elsevier BV
Date: 05-2016
A past, present and future perspective on the European summer vapour pressure deficit
Publisher: Copernicus GmbH
Date: 09-02-2022
DOI: 10.5194/ESSD-2022-47
Abstract: Abstract. The response of evapotranspiration to anthropogenic warming is of critical importance to the water and carbon cycle. Con-flicting observations about changes of evapotranspiration stem mostly from the brevity of observations in time and space as well as a high degree of internal variability. Here we present the first gridded reconstruction of the European summer vapour pressure deficit (VPD) for the past four centuries. The gridded reconstruction is based on 26 European tree-ring oxygen iso-tope records and is performed using a Random Forest approach. Based on our reconstruction, we show that from the mid-1700s a trend towards higher VPD occurred in Central Europe and the Mediterranean region which is based on the simulta-neous increase in temperature and decrease in precipitation. This increasing VPD trend continues throughout the observation-al period and recent times. Climate model projections show this increase in VPD for the Mediterranean region continuing until the end of the 21st century, whereby the extent depends on the amount of greenhouse gas emissions. In contrast, pro-jected VPD in North and Central Europe shows a tendency towards higher VPD only in the highest emission scenario (the produced data is available here: 0.5281/zenodo.5958837 (Balting, D. F. et al., 2022).
Micromagnetic Tomography for Paleomagnetism and Rock‐Magnetism
Publisher: American Geophysical Union (AGU)
Date: 10-2021
DOI: 10.1029/2021JB022364
Abstract: Our understanding of the past behavior of the geomagnetic field arises from magnetic signals stored in geological materials, e.g., (volcanic) rocks. Bulk rock s les, however, often contain magnetic grains that differ in chemistry, size, and shape some of them record the Earth's magnetic field well, others are unreliable. The presence of a small amount of adverse behaved magnetic grains in a s le may already obscure important information on the past state of the geomagnetic field. Recently it was shown that it is possible to determine magnetizations of in idual grains in a s le by combining X‐ray computed tomography and magnetic surface scanning measurements. Here we establish this new Micromagnetic Tomography (MMT) technique and make it suitable for use with different magnetic scanning techniques, and for both synthetic and natural s les. We acquired reliable magnetic directions by selecting subsets of grains in a synthetic s le, and we obtained rock‐magnetic information of in idual grains in a volcanic s le. This illustrates that MMT opens up entirely new venues of paleomagnetic and rock‐magnetic research. MMT's unique ability to determine the magnetization of in idual grains in a nondestructive way allows for a systematic analysis of how geological materials record and retain information on the past state of the Earth's magnetic field. Moreover, by interpreting only the contributions of known magnetically well‐behaved grains in a s le, MMT has the potential to unlock paleomagnetic information from even the most complex, crucial, or valuable recorders that current methods are unable to recover.
Relationship between wood anatomy, tree-ring widths and wood density of Pinus sylvestris L. and climate at high latitudes in northern Sweden
Publisher: Elsevier BV
Date: 2014
Global Peak in Atmospheric Radiocarbon Provides a Potential Definition for the Onset of the Anthropocene Epoch in 1965
Publisher: Springer Science and Business Media LLC
Date: 19-02-2018
DOI: 10.1038/S41598-018-20970-5
Abstract: Anthropogenic activity is now recognised as having profoundly and permanently altered the Earth system, suggesting we have entered a human-dominated geological epoch, the ‘Anthropocene’. To formally define the onset of the Anthropocene, a synchronous global signature within geological-forming materials is required. Here we report a series of precisely-dated tree-ring records from C bell Island (Southern Ocean) that capture peak atmospheric radiocarbon ( 14 C) resulting from Northern Hemisphere-dominated thermonuclear bomb tests during the 1950s and 1960s. The only alien tree on the island, a Sitka spruce ( Picea sitchensis ), allows us to seasonally-resolve Southern Hemisphere atmospheric 14 C, demonstrating the ‘bomb peak’ in this remote and pristine location occurred in the last-quarter of 1965 (October-December), coincident with the broader changes associated with the post-World War II ‘Great Acceleration’ in industrial capacity and consumption. Our findings provide a precisely-resolved potential Global Stratotype Section and Point (GSSP) or ‘golden spike’, marking the onset of the Anthropocene Epoch.
Micromagnetic Tomography for Paleomagnetism and Rock-Magnetism
Publisher: Wiley
Date: 07-09-2021
Tree-ring radiocarbon reveals reduced solar activity during Younger Dryas cooling
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-11654
Abstract: & & The Younger Dryas stadial (YD) was a return to glacial-like conditions in the North Atlantic region that interrupted deglacial warming around 12900 cal BP (before 1950 AD). Terrestrial and marine records suggest this event was initiated by the interruption of deep-water formation arising from North American freshwater runoff, but the causes of the millennia-long duration remain unclear. To investigate the solar activity, a possible YD driver, we exploit the cosmic production signals of tree-ring radiocarbon (& sup& & /sup& C) and ice-core beryllium-10 (& sup& & /sup& Be). Here we present the highest temporally resolved dataset of & sup& & /sup& C measurements (n = 1558) derived from European tree rings that have been accurately extended back to 14226 cal BP (& #177 , 2-& #963 ), allowing precise alignment of ice-core records across this period. We identify a substantial increase in & sup& & /sup& C and & sup& & /sup& Be production starting at 12780 cal BP is comparable in magnitude to the historic Little Ice Age, being a clear sign of grand solar minima. We hypothesize the timing of the grand solar minima provides a significant lifying factor leading to the harsh sustained glacial-like conditions seen in the YD.& &
Supplementary material to "Large scale climate signals of a European oxygen isotope network from tree-rings – predominantly caused by ENSO teleconnections?"
Publisher: Copernicus GmbH
Date: 30-03-2020
A past and present perspective on the European summer vapour pressure deficit
Publisher: Copernicus GmbH
Date: 08-06-2023
DOI: 10.5194/CP-2023-35
Abstract: Abstract. The response of evapotranspiration to anthropogenic warming is of critical importance for the water and carbon cycle. Contradictory conclusions about evapotranspiration changes are caused primarily by their brevity in time and sparsity in space, as well as the strong influence of internal variability. Here, we present the first gridded reconstruction of the summer vapour pressure deficit (VPD) for the past four centuries at the European level. This gridded reconstruction is based on 26 European tree-ring oxygen isotope records and is obtained using a Random Forest approach. Based on our reconstruction, we show that from the mid- 1700s, a trend towards higher VPD occurred in Central Europe and the Mediterranean region which is related to a simultaneous increase in temperature and decrease in precipitation. This increasing VPD trend continues throughout the observational period and in recent times. Moreover, our VPD reconstruction helps to visualize the local and regional impacts of the current climate change as well as to minimize statistical uncertainties of historical VPD variability. Furthermore, the interdisciplinary use of the data should be emphasized, as VPD is a crucial parameter for many climatological feedback processes in the earth surface system. The reconstructed VPD gridded data, over the last 400 years, is available at the following link: 0.5281/zenodo.5958836 (Balting, D. F. et al., 2022).
Related Organisations
University Of Southampton
Location: United Kingdom of Great Britain and Northern Ireland
Universidad Técnica Federico Santa María Departamento De Física
Location: Chile
Related Funding Activities
No related grants have been discovered for Gerhard Helle.