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  • 1
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    Interdecadal Pacific Oscillation in Northern Greenland Dust Concentration Variability During the Last 400 Years (2022)
    Details
    Publication Date: 2023-09-13
    Description: Statistical analysis of reanalysis and observed data reveals that high dust surface mass concentration in northern Greenland is associated with a Pacific Decadal Oscillation like pattern in its negative phase in the North Pacific as well as with La Niña conditions in the tropical Pacific region. The sea surface temperature anomalies in the Pacific realm resemble the Interdecadal Pacific Oscillation (IPO). The associated atmospheric circulation pattern, in the form of a wave‐train from the North Pacific to the Eurasian continent, favors enhanced dust uptake and transport toward the northern Greenland. Similar patterns are associated with a low‐resolution stacked record of five Ca2+ ice cores, that is, ngt03C93.2 (B16), ngt14C93.2 (B18), ngt27C94.2 (B21), GISP2−B, and NEEM‐2011‐S1, from northern Greenland, a proxy for regional dust concentration, during the last 400 years. We argue that northern Greenland ice core dust records could be used as proxies for the IPO and related teleconnections.
    Description: Plain Language Summary: Observational and modeling studies show that, during the observational period, interannual to multidecadal dust concentration variability is related to the dominant modes of climate variability at these time scales. Here we show that Interdecadal Pacific Oscillation (IPO) signal is robustly recorded in low‐resolution dust ice core records from the northern Greenland during the last 400 years. We argue that northern Greenland ice core dust records could be used to put the IPO activity and related teleconnections during the observational period into a long‐term perspective.
    Description: Key Points: Northern Greenland dust concentration variability shows global teleconnections during the instrumental period. The most stable pattern associated with northern Greenland ice core dust variability is the Interdecadal Pacific Oscillation (IPO). Northern Greenland ice core dust records could be used as a complementary source of information about IPO during the past.
    Description: Changing Earth—Sustaining our Future
    Description: Helmholtz Climate Initiative—REKLIM
    Description: https://doi.org/10.1594/PANGAEA.57092
    Description: https://doi.org/10.1594/PANGAEA.57294
    Description: https://doi.org/10.1594/PANGAEA.107285
    Description: https://doi.org/10.1594/PANGAEA.55536
    Description: https://disc.gsfc.nasa.gov/datasets?project=MERRA-2
    Description: https://psl.noaa.gov/data/gridded/data.cobe.html
    Description: https://psl.noaa.gov/data/gridded/data.20thC_ReanV2c.html
    Description: https://www.ncdc.noaa.gov/paleo-search/study/33092
    Description: https://www.wdc-climate.de/ui/entry?acronym=EKF400_v2.0
    Keywords: ddc:551.6 ; dust concentration ; northern Greenland ; Interdecadal Pacific Oscillation ; ice cores
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    Past megadroughts in central Europe were longer, more severe and less warm than modern droughts (2021)
    Nature Publishing Group UK
    Details
    Publication Date: 2023-07-20
    Description: Megadroughts are notable manifestations of the American Southwest, but not so much of the European climate. By using long-term hydrological and meteorological observations, as well as paleoclimate reconstructions, here we show that central Europe has experienced much longer and severe droughts during the Spörer Minimum (~AD 1400–1480) and Dalton Minimum (~AD 1770–1840), than the ones observed during the 21st century. These two megadroughts appear to be linked with a cold state of the North Atlantic Ocean and enhanced winter atmospheric blocking activity over the British Isles and western part of Europe, concurrent with reduced solar forcing and explosive volcanism. Moreover, we show that the recent drought events (e.g., 2003, 2015, and 2018), are within the range of natural variability and they are not unprecedented over the last millennium.
    Description: Central Europe experienced long-lasting droughts during the Spörer and Dalton solar minima around AD 1450 and 1800 that were more severe and extensive than those observed in the 21st century, according to palaeoclimate reconstructions.
    Keywords: ddc:551.6 ; Climate sciences ; Hydrology ; Central Europe ; megadroughts
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 3
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    Evaluation of Labrador Sea water formation in a global finite-element sea-ice ocean model setup based on a comparison with observational data (2014)
    Wiley-Blackwell
    Details
    Publication Date: 2014-01-09
    Description: The deep water formation in the Labrador Sea is simulated with the Finite-Element Sea-Ice Ocean Model (FESOM) in a regionally focused, but globally covered model setup. The model has a regional resolution of up to 7 km and the simulations cover the time period 1958-2009. We evaluate the capability of the model setup to reproduce a realistic deep water formation in the Labrador Sea. Two classes of modeled Labrador Sea Water (LSW), the lighter upper LSW (uLSW) and the denser deep LSW (dLSW), are analysed. Their layer thicknesses are compared to uLSW and dLSW layer thicknesses derived from observations in the formation region for the time interval 1988-2009. The results indicate a suitable agreement between the modeled and from observations derived uLSW and dLSW layer thicknesses except for the period 2003-2007 where deviations in the modeled and observational derived layer thickness could be linked to discrepancies in the atmospheric forcing of the model. It is shown that the model is able to reproduce four phases in the temporal evolution of the potential density, temperature and salinity, since the late 1980s, which are known in observational data. These four phases are characterized by a significantly different LSW formation. The first phase from 1988 to 1990 is characterized in the model by a fast increase in the convection depth of up to 2000 m, accompanied by an increased Spring production of deep Labrador Sea Water (dLSW). In the second phase (1991-1994), the dLSW layer thickness remains on a high level for several years, while the third phase (1995-1998) features a gradual decrease in the deep ventilation and the renewal of the deep ocean layers. The fourth phase from 1999 to 2009 is characterized by a slowly continuing decrease of the dLSW layer thickness on a deeper depth level. By applying a Composite Map Analysis between an index of dLSW and sea level pressure over the entire simulation period from 1958 to 2009, it is shown that a pattern which resembles the structure of the North Atlantic Oscillation (NAO) is one of the main triggers for the variability of LSW formation. Our model results indicate that the process of dLSW formation can act as a low-pass filter to the atmospheric forcing, so that only persistent NAO events have an effect, whether uLSW or dLSW is formed. Based on composite maps of the thermal and haline contributions to the surface density flux we can demonstrate that the central Labrador Sea in the model is dominated by the thermal contributions of the surface density flux, while the haline contributions are stronger over the branch of the Labrador Sea boundary current system (LSBCS), where they are dominated by the haline contributions of sea ice melting and formation. Our model results feature a shielding of the central Labrador Sea from the haline contributions by the LSBCS, which only allows a minor haline interaction with the central Labrador Sea by lateral mixing. Based on the comparison of the simulated and measured LSW layer thicknesses as well as vertical profiles of potential density, temperature and salinity it is shown that the FESOM model is a suitable tool to study the regional dynamics of LSW formation and its impact on a global, not regional restricted, scale.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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    PAPER CURRENT
  • 4
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    Atmospheric circulation patterns associated with the variability of River Ammer floods: evidence from observed and proxy data (2016)
    In:  Climate of the Past
    Details
    Publication Date: 2020-02-12
    Description: The relationship between the frequency of River Ammer floods (southern Germany) and atmospheric circulation variability is investigated based on observational Ammer River discharge data back to 1926 and a flood layer time series from varved sediments of the downstream Lake Ammer for the pre-instrumental period back to 1766. A composite analysis reveals that, at synoptic timescales, observed River Ammer floods are associated with enhanced moisture transport from the Atlantic Ocean and the Mediterranean towards the Ammer region, a pronounced trough over western Europe as well as enhanced potential vorticity at upper levels. We argue that this synoptic-scale configuration can trigger heavy precipitation and floods in the Ammer region. Interannual to multidecadal increases in flood frequency, as detected in the instrumental discharge record, are associated with a wave train pattern extending from the North Atlantic to western Asia, with a prominent negative center over western Europe. A similar atmospheric circulation pattern is associated with increases in flood layer frequency in the Lake Ammer sediment record during the pre-instrumental period. We argue that the complete flood layer time series from Lake Ammer sediments covering the last 5500 years contains information about atmospheric circulation variability on interannual to millennial timescales.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 5
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    Atmospheric circulation patterns associated to the variability of River Ammer floods: evidence from observed and proxy data (2016)
    In:  Geophysical Research Abstracts, Vol. 18, EGU2016-5574
    Details
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/conferenceObject
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  • 6
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    Panta Rhei benchmark dataset: socio-hydrological data of paired events of floods and droughts (2022)
    GFZ Data Services
    Details
    Publication Date: 2023-01-18
    Description: As the negative impacts of hydrological extremes increase in large parts of the world, a better understanding of the drivers of change in risk and impacts is essential for effective flood and drought risk management and climate adaptation. However, there is a lack of comprehensive, empirical data about the processes, interactions and feedbacks in complex human-water systems leading to flood and drought impacts. To fill this gap, we present an IAHS Panta Rhei benchmark dataset containing socio-hydrological data of paired events, i.e. two floods or two droughts that occurred in the same area (Kreibich et al. 2017, 2019). The contained 45 paired events occurred in 42 different study areas (in three study areas we have data on two paired events), which cover different socioeconomic and hydroclimatic contexts across all continents. The dataset is unique in covering floods and droughts, in the number of cases assessed and in the amount of qualitative and quantitative socio-hydrological data contained. References to the data sources are provided in 2022-002_Kreibich-et-al_Key_data_table.xlsx where possible. Based on templates, we collected detailed, review-style reports describing the event characteristics and processes in the case study areas, as well as various semi-quantitative data, categorised into management, hazard, exposure, vulnerability and impacts. Sources of the data were classified as follows: scientific study (peer-reviewed paper and PhD thesis), report (by governments, administrations, NGOs, research organisations, projects), own analysis by authors, based on a database (e.g. official statistics, monitoring data such as weather, discharge data, etc.), newspaper article, and expert judgement. The campaign to collect the information and data on paired events started at the EGU General Assembly in April 2019 in Vienna and was continued with talks promoting the paired event data collection at various conferences. Communication with the Panta Rhei community and other flood and drought experts identified through snowballing techniques was important. Thus, data on paired events were provided by professionals with excellent local knowledge of the events and risk management practices.
    Language: English
    Type: info:eu-repo/semantics/workingPaper
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  • 7
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    Interpreting historical, botanical, and geological evidence to aid preparations for future floods (2019)
    In:  Wiley Interdisciplinary Reviews: Water
    Details
    Publication Date: 2020-05-08
    Description: River flooding is among the most destructive of natural hazards globally, causing widespread loss of life, damage to infrastructure and economic deprivation. Societies are currently under increasing threat from such floods, predominantly from increasing exposure of people and assets in flood-prone areas, but also as a result of changes in flood magnitude, frequency, and timing. Accurate flood hazard and risk assessment are therefore crucial for the sustainable development of societies worldwide. With a paucity of hydrological measurements, evidence from the field offers the only insight into truly extreme events and their variability in space and time. Historical, botanical, and geological archives have increasingly been recognized as valuable sources of extreme flood event information. These different archives are here reviewed with a particular focus on the recording mechanisms of flood information, the historical development of the methodological approaches and the type of information that those archives can provide. These studies provide a wealthy dataset of hundreds of historical and palaeoflood series, whose analysis reveals a noticeable dominance of records in Europe. After describing the diversity of flood information provided by this dataset, we identify how these records have improved and could further improve flood hazard assessments and, thereby, flood management and mitigation plans.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 8
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    Interannual to millennial‐scale variability of River Ammer floods and its relationship with solar forcing (2021)
    In:  International Journal of Climatology
    Details
    Publication Date: 2022-01-10
    Description: The relationship between River Ammer flood frequency variability, extreme summer climate over Europe, and solar forcing is investigated. First, we used observational data to evaluate extreme weather and climate anomaly patterns associated with flood and solar forcing as well as the possible dynamical mechanisms behind them. Then, the annual resolution flood layer record from the Lake Ammer sediments is analysed to evaluate millennial‐scale variability of floods and possible related extreme climate patterns back to 5,500 years BP. A composite analysis reveals that observed River Ammer flood frequency variability at interannual to multidecadal time scales is connected to large‐scale extreme precipitation and temperature patterns. From a synoptic‐scale perspective, the extreme precipitation pattern associated with floods is related to an increase in the frequency of high upper‐level potential vorticity (PV) events over western Europe and a decrease over eastern Europe and western Russia. Increased (decreased) frequency of upper‐level high PV events is related to more (less) surface extreme precipitation occurrence. Furthermore, we show that increased frequency of upper‐level high PV events over western Europe is associated with enhanced blocking activity over eastern Europe. Therefore, the out of phase interannual to millennial‐scale variations of River Ammer flood frequency and solar irradiance, as presented in previous studies, can be explained by a solar modulation of eastern European‐western Russia summer blocking and associated upstream upper‐level wave breaking activity. In addition, we identify two distinct quasi‐periodic signals in both frequency of Lake Ammer flood layer and solar irradiance records with periods of ~900 years and ~2,300 years. We argue that similar cycles should dominate millennial‐scale variations of blocking activity in eastern Europe‐western Russia as well as extreme precipitation and flood frequency variability over central and western Europe during the last ~5,500 years.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 9
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    What we talk about when we talk about seasonality – A transdisciplinary review (2022)
    In:  Earth-Science Reviews
    Details
    Publication Date: 2022-01-19
    Description: The role of seasonality is indisputable in climate and ecosystem dynamics. Seasonal temperature and precipitation variability are of vital importance for the availability of food, water, shelter, migration routes, and raw materials. Thus, understanding past climatic and environmental changes at seasonal scale is equally important for unearthing the history and for predicting the future of human societies under global warming scenarios. Alas, in palaeoenvironmental research, the term ‘seasonality change’ is often used liberally without scrutiny or explanation as to which seasonal parameter has changed and how. Here we provide fundamentals of climate seasonality and break it down into external (insolation changes) and internal (atmospheric CO2 concentration) forcing, and regional and local and modulating factors (continentality, altitude, large-scale atmospheric circulation patterns). Further, we present a brief overview of the archives with potentially annual/seasonal resolution (historical and instrumental records, marine invertebrate growth increments, stalagmites, tree rings, lake sediments, permafrost, cave ice, and ice cores) and discuss archive-specific challenges and opportunities, and how these limit or foster the use of specific archives in archaeological research. Next, we address the need for adequate data-quality checks, involving both archive-specific nature (e.g., limited sampling resolution or seasonal sampling bias) and analytical uncertainties. To this end, we present a broad spectrum of carefully selected statistical methods which can be applied to analyze annually- and seasonally-resolved time series. We close the manuscript by proposing a framework for transparent communication of seasonality-related research across different communities.
    Type: info:eu-repo/semantics/article
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  • 10
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    Large-scale climate signals of a European oxygen isotope network from tree rings (2021)
    In:  Climate of the Past
    Details
    Publication Date: 2021-06-23
    Description: 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.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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