scholarly journals Effects of dating errors on nonparametric trend analyses of speleothem time series

2012 ◽  
Vol 8 (5) ◽  
pp. 1637-1648 ◽  
Author(s):  
M. Mudelsee ◽  
J. Fohlmeister ◽  
D. Scholz
Keyword(s):  
Time Series ◽  
Quantitative Methods ◽  
Fundamental Problem ◽  
Age Determination ◽  
Winter Precipitation ◽  
Oxygen Isotopic Composition ◽  
Ice Age ◽  
Climate Trends ◽  
Winter Climate ◽  
Millennial Scale

Abstract. A fundamental problem in paleoclimatology is to take fully into account the various error sources when examining proxy records with quantitative methods of statistical time series analysis. Records from dated climate archives such as speleothems add extra uncertainty from the age determination to the other sources that consist in measurement and proxy errors. This paper examines three stalagmite time series of oxygen isotopic composition (δ18O) from two caves in western Germany, the series AH-1 from the Atta Cave and the series Bu1 and Bu4 from the Bunker Cave. These records carry regional information about past changes in winter precipitation and temperature. U/Th and radiocarbon dating reveals that they cover the later part of the Holocene, the past 8.6 thousand years (ka). We analyse centennial- to millennial-scale climate trends by means of nonparametric Gasser–Müller kernel regression. Error bands around fitted trend curves are determined by combining (1) block bootstrap resampling to preserve noise properties (shape, autocorrelation) of the δ18O residuals and (2) timescale simulations (models StalAge and iscam). The timescale error influences on centennial- to millennial-scale trend estimation are not excessively large. We find a "mid-Holocene climate double-swing", from warm to cold to warm winter conditions (6.5 ka to 6.0 ka to 5.1 ka), with warm–cold amplitudes of around 0.5‰ δ18O; this finding is documented by all three records with high confidence. We also quantify the Medieval Warm Period (MWP), the Little Ice Age (LIA) and the current warmth. Our analyses cannot unequivocally support the conclusion that current regional winter climate is warmer than that during the MWP.

scholarly journals Effects of dating errors on nonparametric trend analyses of speleothem time series

2012 ◽  
Vol 8 (3) ◽  
pp. 1973-2005 ◽  
Author(s):  
M. Mudelsee ◽  
J. Fohlmeister ◽  
D. Scholz
Keyword(s):  
Time Series ◽  
Quantitative Methods ◽  
Fundamental Problem ◽  
Age Determination ◽  
Winter Precipitation ◽  
Oxygen Isotopic Composition ◽  
Ice Age ◽  
Climate Trends ◽  
Winter Climate ◽  
Millennial Scale

Abstract. A fundamental problem in paleoclimatology is to take fully into account the various error sources when examining proxy records with quantitative methods of statistical time series analysis. Records from dated climate archives such as speleothems add extra uncertainty from the age determination to the other sources that consist in measurement and proxy errors. This paper examines three stalagmite time series of oxygen isotopic composition (δ18O) from two caves in Western Germany, the series AH-1 from the Atta cave and the series Bu1 and Bu4 from the Bunker cave. These records carry regional information about past changes in winter precipitation and temperature. U/Th and radiocarbon dating reveals that they cover the later part of the Holocene, the past 8.6 thousand years (ka). We analyse centennial- to millennial-scale climate trends by means of nonparametric Gasser-Müller kernel regression. Error bands around fitted trend curves are determined by combining (1) block bootstrap resampling to preserve noise properties (shape, autocorrelation) of the δ18O residuals and (2) timescale simulations (models StalAge and iscam). The timescale error influences on centennial- to millennial-scale trend estimation are not excessively large. We find a "mid-Holocene climate double-swing", from warm to cold to warm winter conditions (6.5 ka to 6.0 ka to 5.1 ka), with warm–cold amplitudes of around 0.5‰ δ18O; this finding is documented by all three records with high confidence. We also quantify the Medieval Warm Period (MWP), the Little Ice Age (LIA) and the current warmth. Our analyses cannot unequivocally support the conclusion that current regional winter climate is warmer than that during the MWP.

scholarly journals Post-LIA glacier changes along a latitudinal transect in the Central Italian Alps

2014 ◽  
Vol 8 (6) ◽  
pp. 2235-2252 ◽  
Author(s):  
R. Scotti ◽  
F. Brardinoni ◽  
G. B. Crosta
Keyword(s):  
Atmospheric Temperature ◽  
Winter Precipitation ◽  
Ice Age ◽  
Glacier Change ◽  
Mass Balances ◽  
Italian Alps ◽  
Temperature Trends ◽  
Continental Divide ◽  
Latitudinal Transect ◽  
Order Of Magnitude

Abstract. The variability of glacier response to atmospheric temperature rise in different topo-climatic settings is still a matter of debate. To address this question in the Central Italian Alps, we compile a post-LIA (Little Ice Age) multitemporal glacier inventory (1860–1954–1990–2003–2007) along a latitudinal transect that originates north of the continental divide in the Livigno Mountains and extends south through the Disgrazia and Orobie ranges, encompassing continental-to-maritime climatic settings. In these sub-regions, we examine the area change of 111 glaciers. Overall, the total glacierized area has declined from 34.1 to 10.1 km2, with a substantial increase in the number of small glaciers due to fragmentation. The average annual decrease (AAD) in glacier area has risen by about 1 order of magnitude from 1860–1990 (Livigno: 0.45; Orobie: 0.42; and Disgrazia: 0.39 % a−1) to 1990–2007 (Livigno: 3.08; Orobie: 2.44; and Disgrazia: 2.27 % a−1). This ranking changes when considering glaciers smaller than 0.5 km2 only (i.e., we remove the confounding caused by large glaciers in Disgrazia), so that post-1990 AAD follows the latitudinal gradient and Orobie glaciers stand out (Livigno: 4.07; Disgrazia: 3.57; and Orobie: 2.47 % a−1). More recent (2007–2013) field-based mass balances in three selected small glaciers confirm post-1990 trends showing the consistently highest retreat in continental Livigno and minimal area loss in maritime Orobie, with Disgrazia displaying transitional behavior. We argue that the recent resilience of glaciers in Orobie is a consequence of their decoupling from synoptic atmospheric temperature trends, a decoupling that arises from the combination of local topographic configuration (i.e., deep, north-facing cirques) and high winter precipitation, which ensures high snow-avalanche supply, as well as high summer shading and sheltering. Our hypothesis is further supported by the lack of correlations between glacier change and glacier attributes in Orobie, as well as by the higher variability in ELA,sub>0 positioning, post-LIA glacier change, and interannual mass balances, as we move southward along the transect.

Warming is Driving Decreases in Snow Fractions While Runoff Efficiency Remains Mostly Unchanged in Snow-Covered Areas of the Western United States

2018 ◽  
Vol 19 (5) ◽  
pp. 803-814 ◽  
Author(s):  
Gregory J. McCabe ◽  
David M. Wolock ◽  
Melissa Valentin
Keyword(s):  
United States ◽  
Time Series ◽  
Winter Precipitation ◽  
Western United States ◽  
Balance Model ◽  
Winter Temperatures ◽  
Long Term Trends ◽  
Monthly Water Balance ◽  
Surface Water Supply

Abstract Winter snowfall and accumulation is an important component of the surface water supply in the western United States. In these areas, increasing winter temperatures T associated with global warming can influence the amount of winter precipitation P that falls as snow S. In this study we examine long-term trends in the fraction of winter P that falls as S (Sfrac) for 175 hydrologic units (HUs) in snow-covered areas of the western United States for the period 1951–2014. Because S is a substantial contributor to runoff R across most of the western United States, we also examine long-term trends in water-year runoff efficiency [computed as water-year R/water-year P (Reff)] for the same 175 HUs. In that most S records are short in length, we use model-simulated S and R from a monthly water balance model. Results for Sfrac indicate long-term negative trends for most of the 175 HUs, with negative trends for 139 (~79%) of the HUs being statistically significant at a 95% confidence level (p = 0.05). Additionally, results indicate that the long-term negative trends in Sfrac have been largely driven by increases in T. In contrast, time series of Reff for the 175 HUs indicate a mix of positive and negative long-term trends, with few trends being statistically significant (at p = 0.05). Although there has been a notable shift in the timing of R to earlier in the year for most HUs, there have not been substantial decreases in water-year R for the 175 HUs.

scholarly journals Projected changes in winter climate in Beskids Mountains during 21st century

Beskydy ◽  
2017 ◽  
Vol 10 (1-2) ◽  
pp. 123-134
Author(s):  
Aleš Farda ◽  
Petr Štěpánek ◽  
Pavel Zahradníček ◽  
Petr Skalák ◽  
Jan Meitner
Keyword(s):  
Water Balance ◽  
21St Century ◽  
Winter Season ◽  
Winter Precipitation ◽  
Balance Budget ◽  
General Increase ◽  
Winter Climate ◽  
Climate Conditions ◽  
Winter Temperatures ◽  
Projected Changes

We have investigated the future changes of climate conditions during the winter season in the Beskids Mountains. During the 21st century mean winter temperature will increase by 2.0–6.3 °C and winter precipitation will increase by 12.5 – to 17.5 % - depending on the scenario. Higher winter temperatures will be reflected in the reduced number of frost days, the number of which may drop by 40 % according to the RCP8.5 scenario. Whilst our study expects general increase in precipitation, higher temperatures will lead to an increased evapotranspiration and also change in the form of precipitation from solid (snow, rime) to liquid (rain, drizzling). Such trends could further propel the unfavorable changes in the water balance budget.

scholarly journals Prediction of Marine Traffic Density Using Different Time Series Model From AIS data of Port Klang and Straits of Malacca

2020 ◽  
Vol 9 (2) ◽  
Author(s):  
Akim Ramin ◽  
Masnawi Mustaffa ◽  
Shaharudin Ahmad
Keyword(s):  
Time Series ◽  
Quantitative Methods ◽  
Exponential Smoothing ◽  
Time Series Model ◽  
Traffic Density ◽  
Identification System ◽  
Ocean Engineering ◽  
Marine Traffic ◽  
Straits Of Malacca ◽  
Port Klang

In the study of ocean engineering, marine traffic is referring to the study of the pattern of the density of ships within the particular boundaries at certain periods. The Port Klang and Straits of Malacca are known for one of the heaviest traffics in Malaysia and the world. The study of traffic within this area is important, because it enables ships to avoid traffic congestion that might happen. Thus, this study is mainly aimed at   predicting or forecasting the density of the ships using the route through this waterway by using quantitative methods which are time-series models and the associative models from the Automatic Identification System (AIS) data. The moving averages, weight moving average, and exponential smoothing for the time series model and associative model have used multiple regression. The results show an exponential smoothing alpha 0.8 and give the lowest MAPE as 20.701%, thereby making this method to be the best in forecasting the future traffic density among the method categories.

scholarly journals Supplemental Material: Contrasting northern and southern European winter climate trends during the Last Interglacial

2021 ◽  
Author(s):  
Sakari Salonen ◽  
et al.
Keyword(s):  
Cross Validation ◽  
Calibration Data ◽  
Climate Trends ◽  
Last Interglacial ◽  
Winter Climate ◽  
Paleoclimate Reconstructions

Paleoclimate reconstructions, pollen–climate calibration data, and cross-validation results.

scholarly journals Climate reconstruction since the Little Ice Age by modelling Koryto glacier, Kamchatka Peninsula, Russia

2008 ◽  
Vol 54 (184) ◽  
pp. 125-130 ◽  
Author(s):  
Satoru Yamaguchi ◽  
Renji Naruse ◽  
Takayuki Shiraiwa
Keyword(s):  
20Th Century ◽  
Meteorological Data ◽  
Ice Core ◽  
Kamchatka Peninsula ◽  
Winter Precipitation ◽  
Ice Age ◽  
Equilibrium Line Altitude ◽  
Ice Cap ◽  
Glacier Terminus ◽  
Tree Ring Data

AbstractBased on the field data at Koryto glacier, Kamchatka Peninsula, Russia, we constructed a one-dimensional numerical glacier model which fits the behaviour of the glacier. The analysis of meteorological data from the nearby station suggests that the recent rapid retreat of the glacier since the mid-20th century is likely to be due to a decrease in winter precipitation. Using the geographical data of the glacier terminus variations from 1711 to 1930, we reconstructed the fluctuation in the equilibrium-line altitude by means of the glacier model. With summer temperatures inferred from tree-ring data, the model suggests that the winter precipitation from the mid-19th to the early 20th century was about 10% less than that at present. This trend is close to consistent with ice-core results from the nearby ice cap in the central Kamchatka Peninsula.

Geochronology - a suitable tool to discern causality from temporal coincidence?

2021 ◽  
Author(s):  
Urs Schaltegger
Keyword(s):  
Time Series ◽  
High Precision ◽  
Age Determination ◽  
System Behavior ◽  
Large Igneous Provinces ◽  
Igneous Provinces ◽  
Volcanic Plumbing System ◽  
Non Linear ◽  
Age Variation ◽  
Non Linear System

<p>Geoscientists tend to subdivide the system Earth into different subsystems (geosphere, hydrosphere, atmosphere, biosphere), which are interacting with each other in a non-linear way. The quantitative understanding of this interaction is essential to make reconstructions of the geological past. This is mostly done by a linear approach of establishing time-series of chemical and physical proxies, calibrating their contemporaneity through geochronology, and eventually invoke causality. A good example is the comparison of carbon or oxygen isotope time series to the paleo-biodiversity in ancient sedimentary sections, temporally correlated using astrochronology or high-precision U-Pb dating of volcanic zircon in interlayered ash beds. While highly accurate and precise data are necessary to form the basis for linear and non-linear models, we have to be aware that any analysis is the result of an experiment – an isotope-chemical analysis in the U-Pb example - introducing random and non-random noise, which can mimic, disturb, distort or mask non-linear system behavior. High-precision/high-accuracy U-Pb age determination using the mineral zircon (ZrSiO4) and application of the techniques of isotope dilution, thermal ionization mass spectrometry is a good example of such an experiment we apply to the geological history of our planet.</p><p>Two examples where precise U-Pb dating methods are used to link disparate processes are (1) using the duration and the tempo of zircon growth in a magmatic system as a measure for modeling magma flux in space and time, and apply these to infer potential eruptibility and volcanic hazard of a plutonic-volcanic plumbing system; (2) establish absolute age and duration of magma emplacement in large igneous provinces, feed these data into models of volatile injection into and residence of volatile species in the atmosphere, estimate their influence on the inherent parameters of Earth’s climate, and infer causality with climatic, environmental and biotic crises. Both of these are outstanding scientific questions that attract and deserve significant attention by a general as well as academic public. However, insufficient attention is drawn onto the questions of the nature and importance of the noise we add through isotopic age determination.</p><p>There are two prominent issues to be discussed in this context, (1) to what extent (at what precision) can we distinguish natural age variation among zircon grains from random scatter produced by analytical techniques and the complexity of the U-Pb isotopic system in zircon, and (2) how can we correlate the U-Pb dates established for crystallization of zircon in residual and/or assimilated melt portions of mafic magmatic rocks from large igneous provinces to the release and injection of magmatic and contact-metamorphic volatiles into the atmosphere? This contribution intends to demonstrate that analytical scatter and complex system behavior are often confounded with age variation (and vice versa) and will outline new approaches and insights how to quantify their respective contributions.</p>

scholarly journals End-of-life management protocol offered within emergency room (EMPOWER): study protocol for a multicentre study

BMJ Open ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. e036598 ◽  
Author(s):  
Rakhee Yash Pal ◽  
Win Sen Kuan ◽  
Ling Tiah ◽  
Ranjeev Kumar ◽  
Yoko Kin Yoke Wong ◽  
...  
Keyword(s):  
Time Series ◽  
Multicentre Study ◽  
End Of Life ◽  
Study Protocol ◽  
Quantitative Methods ◽  
Local Context ◽  
Resource Utilisation ◽  
Care Protocol ◽  
Management Protocol ◽  
Eol Care

BackgroundPatients at their end-of-life (EOL) phase frequently visit the emergency department (ED) due to their symptoms, yet the environment and physicians in ED are not traditionally equipped or trained to provide palliative care. This multicentre study aims to measure the current quality of EOL care in ED to identify gaps, formulate improvements and implement the improved EOL care protocol. We shall also evaluate healthcare resource utilisation and its associated costs.Methods and analysisThis study employs a quasiexperimental interrupted time series design using both qualitative and quantitative methods, involving the EDs of three tertiary hospitals in Singapore, over a period of 3 years. There are five phases in this study: (1) retrospective chart reviews of patients who died within 5 days of ED attendance; (2) pilot phase to validate the CODE questionnaire in the local context; (3) preimplementation phase; (4) focus group discussions (FGDs); and (5) postimplementation phase. In the prospective cohort, patients who are actively dying or have high likelihood of mortality this admission, and whose goal of care is palliation, will be eligible for inclusion. At least 140 patients will be recruited for each preimplementation and postimplementation phase. There will be face-to-face interviews with patients’ family members, review of medical records and self-administered staff survey to evaluate existing knowledge and confidence. The FGDs will involve hospital and community healthcare providers. Data obtained from the retrospective cohort, preimplementation phase and FGDs will be used to guide prospective improvement and protocol changes. Patient, family and staff relevant outcomes from these changes will be measured using time series regression.Ethics and disseminationThe study protocol has been reviewed and ethics approval obtained from the National Healthcare Group Domain Specific Review Board, Singapore. The results from this study will be actively disseminated through manuscript publications and conference presentations.Trial registration numberNCT03906747.

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