Transient state estimation in paleoclimatology using data assimilation

Data assimilation methods used for transient atmospheric state estimations in paleoclimatology such as covariance-based approaches, analogue techniques and nudging are briefly introduced. With applications differing widely, a plurality of approaches appears to be the logical way forward.

Late Holocene summer temperatures in the central Andes reconstructed from the sediments of high-elevatin Laguna Chepical, Chile (32° S)

High-resolution reconstructions of climate variability that cover the past millennia are necessary to improve the understanding of natural and anthropogenic climate change across the globe. Although numerous records are available for the mid- and high-latitudes of the Northern Hemisphere, global assessments are still compromised by the scarcity of data from the Southern Hemisphere. This is particularly the case for the tropical and subtropical areas. In addition, high elevation sites in the South American Andes may provide insight into the vertical structure of climate change in the mid-troposphere. This study presents a 3000 yr-long austral summer (November to February) temperature reconstruction derived from the 210Pb- and 14C-dated organic sediments of Laguna Chepical (32°16' S, 70°30' W, 3050 m a.s.l.), a high-elevation glacial lake in the subtropical Andes of central Chile. Scanning reflectance spectroscopy in the visible light range provided the spectral index R570/R630, which reflects the clay mineral content in lake sediments. For the calibration period (AD 1901–2006), the R570/R630 data were regressed against monthly meteorological reanalysis data, showing that this proxy was strongly and significantly correlated with mean summer (NDJF) temperatures (R3 yr = −0.63, padj = 0.01). This calibration model was used to make a quantitative temperature reconstruction back to 1000 BC. The reconstruction (with a model error RMSEPboot of 0.33 °C) shows that the warmest decades of the past 3000 yr occurred during the calibration period. The 19th century (end of the Little Ice Age (LIA)) was cool. The prominent warmth reconstructed for the 18th century, which was also observed in other records from this area, seems systematic for subtropical and southern South America but remains difficult to explain. Except for this warm period, the LIA was generally characterized by cool summers. Back to AD 1400, the results from this study compare remarkably well to low altitude records from the Chilean Central Valley and southern South America. However, the reconstruction from Laguna Chepical does not show a warm Medieval Climate Anomaly during the 12–13th century, which is consistent with records from tropical South America. The Chepical record also indicates substantial cooling prior to 800 BC. This coincides with well-known regional as well as global glacier advances which have been attributed to a grand solar minimum. This study thus provides insight into the climatic drivers and temperature patterns in a region for which currently very few data are available. It also shows that since ca. AD 1400, long-term temperature patterns were generally similar at low and high altitudes in central Chile.

Overview of data assimilation methods

We present the data assimilation approach, which provides a framework for combining observations and model simulations of the climate system, and has led to a new field of applications for paleoclimatology. The three subsequent articles explore specific applications in more detail.

Supporting, Regulating, and Provisioning Hydrological Services

The natural regulation of the water cycle by tropical montane forests is an important ecosystem service. Within this chapter we focus on water balance and regulation of the water cycle. Differences of rainfall-runoff generation across scales change from a near-surface event water driven system in pristine rainforest-covered micro-catchments to a more groundwater pre-event water dominated one on the mesoscale. The highly dynamic discharges are often correlated with total suspended sediment loads. However, we also observed total suspended sediment peaks at times of low flow, indicating a decoupling of erosion and stream transport and a triggering of landslides not directly related to hydrological processes. We also summarize likely future trends of water-related ecosystem services and expect an increase in human use and benefits of fresh water use whereas changes in water regulation and water purification services remain unchanged on a high level.

Science for the Carpathians: Using Regional Capacity to Cope with Global Change

Emphasizing the global and regional importance of mountain ecosystem services and referring to the anticipated future environmental changes affecting the provision of these services, this chapter takes a closer look at the Carpathian Mountains. In addition to climate change and general effects of globalization, rapid socioeconomic transformations after the fall of the Iron Curtain pose an extra challenge to the sustainable development of the region. Describing the early efforts of organizing mountain science through programs such as UNESCO MAB and UNEP at the global scale, this chapter focuses on the recent history of research coordination for the European mountains, in particular on the activities of the Carpathian Convention and the European Program of the Mountain Research Initiative, which were among main driving factors for the initiation of the Science for the Carpathians (S4C) network. This regional mountain research network was established in 2008 to foster scientific collaboration and communication and to promote applied research and capacity building, which in turn would support sustainable development in the Carpathian Mountains. Forum Carpaticum, a biennial open science conference, has become a central activity of the S4C network counting more than 400 members today.

Bevezető: utak és úton lévők

A kvalitatív módszerekkel nyert kutatási eredményeink értelmezése során a transznacionális tér, a transznacionális és az etnikai migráció elméleti és szemléleti kereteit egyaránt figyelembe vettük. Az általunk vizsgált migrációs folyamatok transznacionális térben zajlanak, és a transznacionális irodalomban leírt migráns élethelyzetek, gyakorlatok – különböző nemzetállamokban elhelyezkedő lokalitásokhoz való egyidejű, bár eltérő intenzitású kötődés, kapcsolatok – több példájával is találkoztunk. Ludger Pries nyomán a transznacionális migrációt és a transznacionális migráns alakját olyan ideáltípusnak tekintettük, amelyhez az egyes migráns utak és helyzetek csupán közelítenek, és empirikus eredményeink alapján azt mondhatjuk, hogy a valóban plurilokális, vagyis a két helyhez való egyidejű, intenzív és tartós kötődés s az ehhez kapcsolódó gyakorlatok csupán a migránsok kisebbségét, illetve a migrációs életpályák egy-egy szakaszát jellemzik. A vizsgált migrációs folyamatokban az etnicitás strukturális tényezőként és a migráns tapasztalatok értelmezési kereteként egyaránt perdöntő szerepet játszik. Az etnikai migráció szakirodalomban tárgyalt mindhárom magyarázó modellje – az anyaországba való hazatérés, a gazdasági okokból való, illetve a kisebbségi létben elszenvedett sérelmek által ösztönzött migráció – alkalmas a migrációt kiváltó és mozgató okok elemzésére, a migráns narratívák értelmezésére, azt azonban nem állíthatjuk, hogy bármelyikük kizárólagos érvényre tehet szert. Más kutatókhoz hasonlóan Rogers Brubaker meghatározását tartjuk a leginkább gyümölcsözőnek, aki az etnikai migráció tág értelmezését használva minden olyan vándorlási folyamatot etnikai migrációnak tekint, amelyben az etnicitás kulturális és szimbolikus tőkeként szabályozó szerepet játszik. This special issue of Tér és Társadalom presents some results of an international research project carried out by researchers from Switzerland, Hungary and Serbia between 2010 and 2012. The topic of the research was “Integrating (Trans-)national Migrants in Transition States” (TRANSMIG) and was financed by the Swiss National Science Foundation (SNSF). The research aimed to explore and interpret migration flows from the Vojvodina (Serbia) to Hungary and from ex-Yugoslav republics to the Vojvodina. In the first period of the last twenty years, wars which contributed to the disintegration of Yugoslavia and the formation of new national states have caused migration flows. After the change of the millennium, educational migration of Vojvodina Hungarian youth can be considered the most important migratory movement from the Vojvodina to Hungary. Labour (economic) migration also occurs, but this cannot be understood as a one-way movement, since in the Hungarian–Serbian border zone migrants from the Vojvodina who already resettled to Hungary commute to the Vojvodina. While interpreting the qualitative research data the theoretical frameworks and approaches of transnational space, transnationalism and ethnic migration were taken into consideration. The migration movement in question occurs in a transnational social space where migrants are in constant motion. By their movements and actions that space is continually recreated. With Ludger Pries we see a transnational migrant as an ideal type to whom individual migratory movements and positions only approximate. Based on our empirical results we can conclude that real pluri-local, intensive and long-lasting bonding to two places at the same time and the relating practices only characterise a minority of migrants and certain sections of migratory careers. In the migration processes studied, ethnicity as a term is needed as a “structural factor” and frame of interpretation to approach migrant experiences. All three explanatory models for ethnic migration – return migration, economic migration, migration motivated by grievances suffered in a minority situation – are suitable to analyse the reasons that initiated migration and kept it in motion. They are helpful in interpreting migrant narratives. However, none of the reasons can claim exclusive validity. Agreeing with other researchers, we find Roger Brubaker’s definition the most useful: Ethnic migration should be comprehended in a broad sense. In addition, every migration can be considered as “ethnically” motivated where ethnicity plays a dominant role as a cultural and symbolic capital.

Forcing of stratospheric chemistry and dynamics during the Dalton Minimum

The response of atmospheric chemistry and dynamics to volcanic eruptions and to a decrease in solar activity during the Dalton Minimum is investigated with the fully coupled atmosphere–ocean chemistry general circulation model SOCOL-MPIOM (modeling tools for studies of SOlar Climate Ozone Links-Max Planck Institute Ocean Model) covering the time period 1780 to 1840 AD. We carried out several sensitivity ensemble experiments to separate the effects of (i) reduced solar ultra-violet (UV) irradiance, (ii) reduced solar visible and near infrared irradiance, (iii) enhanced galactic cosmic ray intensity as well as less intensive solar energetic proton events and auroral electron precipitation, and (iv) volcanic aerosols. The introduced changes of UV irradiance and volcanic aerosols significantly influence stratospheric dynamics in the early 19th century, whereas changes in the visible part of the spectrum and energetic particles have smaller effects. A reduction of UV irradiance by 15%, which represents the presently discussed highest estimate of UV irradiance change caused by solar activity changes, causes global ozone decrease below the stratopause reaching as much as 8% in the midlatitudes at 5 hPa and a significant stratospheric cooling of up to 2 °C in the mid-stratosphere and to 6 °C in the lower mesosphere. Changes in energetic particle precipitation lead only to minor changes in the yearly averaged temperature fields in the stratosphere. Volcanic aerosols heat the tropical lower stratosphere, allowing more water vapour to enter the tropical stratosphere, which, via HOx reactions, decreases upper stratospheric and mesospheric ozone by roughly 4%. Conversely, heterogeneous chemistry on aerosols reduces stratospheric NOx, leading to a 12% ozone increase in the tropics, whereas a decrease in ozone of up to 5% is found over Antarctica in boreal winter. The linear superposition of the different contributions is not equivalent to the response obtained in a simulation when all forcing factors are applied during the Dalton Minimum (DM) – this effect is especially well visible for NOx/NOy. Thus, this study also shows the non-linear behaviour of the coupled chemistry-climate system. Finally, we conclude that especially UV and volcanic eruptions dominate the changes in the ozone, temperature and dynamics while the NOx field is dominated by the energetic particle precipitation. Visible radiation changes have only very minor effects on both stratospheric dynamics and chemistry.

Modern sea surface productivity and temperature estimations off Chile as detected by coccolith accumulation rates

Recent coccoliths from 74 surface sediment samples recovered from the southeastern Pacific off Chile were examined quantitatively to investigate modern regional gradients of sea surface productivity and temperature. All findings are based on coccolith accumulation rates. Therefore an approach was designed to estimate recent sedimentation rates based on 210Pb and bulk chemistry analyses of the same set of surface samples. Highest total coccolith accumulation rates were found off north-central Chile, where seasonal upwelling takes place. Based on a multiple linear regression between calculated coccolith accumulation rates and World Ocean Atlas derived sea surface temperatures, a calibration model to reconstruct annual average temperatures of the uppermost 75 m of the water column is provided. The model was cross-validated and the SST estimates were compared with SST observed and SST estimates based on diatoms and planktonic foraminifera, showing a good correlation.

Modeling the stratospheric warming following the Mt. Pinatubo eruption: uncertainties in aerosol extinctions

In terms of atmospheric impact, the volcanic eruption of Mt. Pinatubo (1991) is the best characterized large eruption on record. We investigate here the model-derived stratospheric warming following the Pinatubo eruption as derived from SAGE II extinction data including recent improvements in the processing algorithm. This method, termed SAGE_4λ, makes use of the four wavelengths (385, 452, 525 and 1024 nm) of the SAGE II data when available, and uses a data-filling procedure in the opacity-induced "gap" regions. Using SAGE_4λ, we derived aerosol size distributions that properly reproduce extinction coefficients also at much longer wavelengths. This provides a good basis for calculating the absorption of terrestrial infrared radiation and the resulting stratospheric heating. However, we also show that the use of this data set in a global chemistry–climate model (CCM) still leads to stronger aerosol-induced stratospheric heating than observed, with temperatures partly even higher than the already too high values found by many models in recent general circulation model (GCM) and CCM intercomparisons. This suggests that the overestimation of the stratospheric warming after the Pinatubo eruption may not be ascribed to an insufficient observational database but instead to using outdated data sets, to deficiencies in the implementation of the forcing data, or to radiative or dynamical model artifacts. Conversely, the SAGE_4λ approach reduces the infrared absorption in the tropical tropopause region, resulting in a significantly better agreement with the post-volcanic temperature record at these altitudes.

Impact of a potential 21st century “grand solar minimum” on surface temperatures and stratospheric ozone

We investigate the effects of a recently proposed 21st century Dalton minimum like decline of solar activity on the evolution of Earth's climate and ozone layer. Three sets of two member ensemble simulations, radiatively forced by a midlevel emission scenario (Intergovernmental Panel on Climate Change RCP4.5), are performed with the atmosphere-ocean chemistry-climate model AOCCM SOCOL3-MPIOM, one with constant solar activity, the other two with reduced solar activity and different strength of the solar irradiance forcing. A future grand solar minimum will reduce the global mean surface warming of 2 K between 1986–2005 and 2081–2100 by 0.2 to 0.3 K. Furthermore, the decrease in solar UV radiation leads to a significant delay of stratospheric ozone recovery by 10 years and longer. Therefore, the effects of a solar activity minimum, should it occur, may interfere with international efforts for the protection of global climate and the ozone layer.

Impact of volcanic stratospheric aerosols on diurnal temperature range in Europe over the past 200 years: Observations versus model simulations

We analyze the impact of stratospheric volcanic aerosols on the diurnal temperature range (DTR) over Europe using long-term subdaily station records. We compare the results with a 28-member ensemble of European Centre/Hamburg version 5.4 (ECHAM5.4) general circulation model simulations. Eight stratospheric volcanic eruptions during the instrumental period are investigated. Seasonal all- and clear-sky DTR anomalies are compared with contemporary (approximately 20 year) reference periods. Clear sky is used to eliminate cloud effects and better estimate the signal from the direct radiative forcing of the volcanic aerosols. We do not find a consistent effect of stratospheric aerosols on all-sky DTR. For clear skies, we find average DTR anomalies of −0.08°C (−0.13°C) in the observations (in the model), with the largest effect in the second winter after the eruption. Although the clear-sky DTR anomalies from different stations, volcanic eruptions, and seasons show heterogeneous signals in terms of order of magnitude and sign, the significantly negative DTR anomalies (e.g., after the Tambora eruption) are qualitatively consistent with other studies. Referencing with clear-sky DTR anomalies to the radiative forcing from stratospheric volcanic eruptions, we find the resulting sensitivity to be of the same order of magnitude as previously published estimates for tropospheric aerosols during the so-called “global dimming” period (i.e., 1950s to 1980s). Analyzing cloud cover changes after volcanic eruptions reveals an increase in clear-sky days in both data sets. Quantifying the impact of stratospheric volcanic eruptions on clear-sky DTR over Europe provides valuable information for the study of the radiative effect of stratospheric aerosols and for geo-engineering purposes.

Tropopause level Rossby wave breaking in the Northern Hemisphere: a feature-based validation of the ECHAM5-HAM climate model

Breaking synoptic-scale Rossby waves (RWB) at the tropopause level are central to the daily weather evolution in the extratropics and the subtropics. RWB leads to pronounced meridional transport of heat, moisture, momentum, and chemical constituents. RWB events are manifest as elongated and narrow structures in the tropopause-level potential vorticity (PV) field. A feature-based validation approach is used to assess the representation of Northern Hemisphere RWB in present-day climate simulations carried out with the ECHAM5-HAM climate model at three different resolutions (T42L19, T63L31, and T106L31) against the ERA-40 reanalysis data set. An objective identification algorithm extracts RWB events from the isentropic PV field and allows quantifying the frequency of occurrence of RWB. The biases in the frequency of RWB are then compared to biases in the time mean tropopause-level jet wind speeds. The ECHAM5-HAM model captures the location of the RWB frequency maxima in the Northern Hemisphere at all three resolutions. However, at coarse resolution (T42L19) the overall frequency of RWB, i.e. the frequency averaged over all seasons and the entire hemisphere, is underestimated by 28%.The higher-resolution simulations capture the overall frequency of RWB much better, with a minor difference between T63L31 and T106L31 (frequency errors of −3.5 and 6%, respectively). The number of large-size RWB events is significantly underestimated by the T42L19 experiment and well represented in the T106L31 simulation. On the local scale, however, significant differences to ERA-40 are found in the higher-resolution simulations. These differences are regionally confined and vary with the season. The most striking difference between T106L31 and ERA-40 is that ECHAM5-HAM overestimates the frequency of RWB in the subtropical Atlantic in all seasons except for spring. This bias maximum is accompanied by an equatorward extension of the subtropical westerlies.

Isotopes Trace Biogeochemistry and Sources of Cu and Zn in an intertidal soil

River floodplain soils are sinks and potential sources for toxic trace metals like Cu and Zn. We hypothesize that stable Cu and Zn isotope ratios reflect both the mobilization and the sources of metals. We determined the soil properties, the concentrations and partitioning of Cu and Zn, and variations in δ65Cu and δ66Zn values in a core obtained from an Aquic Udifluvent developed on a freshwater intertidal mudflat of the River Elbe, Germany. The core was sampled at 2 cm intervals to a depth of 34 cm, which corresponds to approximately 9 yr of sedimentation. Elevated concentrations of Cu (up to 320 μg g−1) and Zn (up to 2080 μg g−1) indicated anthropogenic pollution. At the time of sampling the redox conditions changed from oxic (Eh 200 to 400 mV, above 22 cm deep) to strongly anoxic conditions (-100 to -200 mV, below 22 cm deep). The δ65Cu values varied systematically with depth (from -0.02 to 0.16‰) and were correlated with the Fe, C, and N concentrations. Although pre-depositional variations cannot be ruled out, the systematic variation with depth suggests post-sedimentation fractionation of δ65Cu in response to seasonally variable organic matter deposition and redox conditions. In contrast, the δ66ZnIRMM values were uniform (from -0.07 to 0.01‰) throughout the core, indicating that the Zn isotopes did not significantly fractionate after deposition and that the Zn sources were homogeneous throughout the sedimentation.