Leszek Starkel

Change in the frequency of extreme events as the indicator of climatic change in the Holocene (in fluvial systems)

Abstract The transformation of natural systems of climatic origin in the Holocene may be realised by a change in the type of extreme events, or by a change in their frequency, or by both. The rapid warming at the Younger Dryas–Preboreal transition exemplifies a parallel drop in frequency and a change in the type of events. Several wetter phases of the Holocene are characterised by rises in frequency of various types of extreme rainfalls. The fragmentary records of events in the fluvial and slope systems coincide with smoothed variations in stable ecosystems and shifts of ecotonal zones (such as tree line and lake levels).

Stable isotopes of Holocene calcareous tufa in southern Poland as paleoclimatic indicators

Abstract The isotopic composition of oxygen in freshwater calcareous tufa seems to be a sensitive indicator of past climatic changes. Results of measurements of δ c 18 O and δ c 13 C in tufa samples dated with the 14 C method are used to reconstruct Holocene climatic changes in southern Poland. Values of δ c 18 O obtained on tufa samples from four sites (Raclawka, Rzerzuŝnia, Trzebienice, Sieradowice) representing different hydrodynamic conditions of tufa sedimentation seem to form a selfconsistent series. These values, with some simplifying assumptions concerning the course of tufa sedimentation, were therefore used to estimate mean annual temperatures in the interval ca. 9500-2000 yr B.P. When the resulting curve of thermal changes in southern Poland is compared with changes of deposition and erosion of tuffaceous sediments and with results of other methods of reconstruction of paleoclimate in central Europe, a reasonable agreement among the different specific methods is seen.

Progress in the holocene chrono-climatostratigraphy of Polish territory

The Holocene delivers a unique possibility to establish climatic stratigraphic boundaries based on detailed chronostratigraphy reflected in various facies of continental sediments, in their lithological parameters and organic remains. These sediments are dated by the 14C method in the case of organic remains, by counting annual laminations in lacustrine facies, and by dendrochronological method in the case of fluvial sediments.The existence of well dated profiles enables to reconstruct various climatic parameters like amplitudes of seasonal temperatures, types and frequency of extreme rainfalls and floods and, finally, to distinguish rare rapid changes and most frequent gradual ones. This reconstruction is based on the analogous effects of various types of present-day rainfalls.The current authors present a critical review of existing chronostratigraphic divisions starting from simple millennial division by Mangerud based on Scandinavian palynological stratigraphy of peat-bogs and Starkel’s concept based on fluctuations in rainfall and runoff regime reflected in fluvial and other facies of continental deposits.In the last decades, the calibration of 14C dates allowed a new approach to be used for the construction of the probability distribution function of these dates in various facies or types of sediments, which formed a background for distinguishing and correlating climatic phases and defining boundaries between them. These approaches have been creating new opportunities for revision of the existing chronostratigraphy.The aim of this paper is to present a revised version of chronostratigraphic division based on climatic fluctuations reflected in various facies of sediments on the territory of Poland and discuss their correlation with other European regions and global climatic changes.

Younger Dryas–Preboreal transition documented in the fluvial environment of Polish rivers

Abstract The rapid climatic change at the Younger Dryas–Preboreal transition has been documented in the sequence of annually laminated sediments of Lake Gościąz in the middle course of the Vistula Valley. The author correlates this key profile with about 50 localities of alluvial sediments and abandoned channels in the Vistula and Warta catchments. Discussed deposits have been radiocarbon-dated. The interpretation is supported by pollen diagrams. It is concluded that in most cases, either abundance of large paleochannels or a change from channel to overbank facies or to organic sedimentation took place just at the transition time. Also, in the fills of the Late glacial paleochannels, a decline in fluvial activity is observed that is evidenced by a change in grain size composition. However, an exact dating of this rapid transition is difficult as it coincides with the radiocarbon plateau at 10 ka BP.

Lake-level and groundwater-level changes in the Lake Gosciąż area, Poland: palaeoclimatic implications

Lake Gosciąz is located in the zone of the maximum extent of the last ice sheet. Distinct lake terraces and deposits related to the lateglacial transgression do not exist. Detailed examination of annually laminated sediments and landforms revealed three phases of higher water level and storage, represented by shore features, by littoral, deltaic and bog deposits, and by higher rates of lacustrine deposition in the pelagic zone. Holocene lake transgressions at c. 8.4-7.7 ka, 2.5-2.3 ka, and less distinct at 5-4 ka BP coincide with phases of higher flood frequency in Poland and glacial advances in the Alps. Because of sedimentation, isolation from groundwaters, encroachment by peatland and drainage of the lake, lake volume during the last 12 ka diminished by as much as 70%, and current water-level fluctuations of about 1-2 m can change water storage by 20-25%.

The response of slope and channel systems to various types of extreme rainfall: A comparison between the temperate zone and humid tropics

Abstract The mountain slopes and river channels of the temperate zone and of the humid tropics are modelled by various types of extreme rainfall. In the Flysch Carpathians the leading role is played by continuous rains causing floods and landslides, rainy seasons (wet years) mobilizing deep landslides and, to a smaller degree by local downpours. In the Darjeeling Himalaya with young relief and uplift tendency, the main influence on modelling the mountain slopes and river channels have been the extreme continuous rains separated by several decades of normal rainy season, playing the preparatory or relaxation role with simultaneous transformation of slopes and river channels. In both cases human impact has caused the acceleration of runoff and mobilization of sediment. The higher extremes of precipitation and steep slopes in the humid tropics are balanced (to some extent) in temperate zones by the lower infiltration rates and lower thresholds of mass mobility on the gentle slopes originated in the periglacial environment.

Hydrological Changes after the Last Ice Retreat in Northern Poland Using Radiocarbon Dating

A simplified model of hydrological changes during the Late Glacial and Holocene is presented for the northern Polish regions that were ice covered during the Last Glacial. This reconstruction is based on a group of 197 radiocarbon dates from about 120 localities reflecting the sequence of alternating lake transgressions and regressions. The earliest transgressions were related to dead-ice melting (sometimes in 2–3 phases), while the later ones started during more humid phases. However, these were usually followed by regressions, which may have been connected with the formation of new drainage systems and with the overgrowing of shallow lakes by peat bogs.

Reconstruction of hydrological changes between 7000 and 3000 BP in the upper and middle Vistula River Basin, Poland:

Rhythmic fluctuations in the hydrological regime are demonstrated based on a review of records sensitive to relative climatic stability between 7000 and 3000 BP in the upper and middle parts of the Vistula River Basin, central Europe. In the fluvial deposits and landforms these variations are very clear; phases of higher flood frequency are dated 6600-6000, 5500-4750, 4500-4100 and 3250-3000 BP. These phases coincide very well with sparse information on landslides, data on high lake levels in the early Subboreal, phases of forest-ecosystem transformation and, finally, the reaction of human cultures to these changes. Their rhythmicity correlates well with records from the Alps and the Alpine foreland but poorly with those from Scandinavia. This may be explained by changes in the zonal pattern of air- mass circulation. Among the causes of the humid phases, it is the frequency of volcanic eruptions which should be taken into consideration.

Frequency of Extreme Hydroclimatically-Induced Events as a Key to Understanding Environmental Changes in the Holocene

Our understanding of past frequencies of extreme hydroclimatically-induced events such as floods and mass wasting is mainly based on direct or indirect interpretations of sediments, landforms and parallel biotic changes. These sources of information point to episodes with higher or lower frequency of extreme events, and indicate that some of these occurred under wetter and cooler conditions that permitted higher water storage (cf. Starkel, 1983). It also seems true that greater year-to-year and multi-year variability have characterized those times of transition when water storage or runoff drastically adjust (e.g. ice sheet decay in North America; Teller, 1995). In the arid zone, such instability can involve high frequency of cyclones, and thus wetter conditions; in the semi-arid zone, in contrast, greater instability may cause expansion of the desert. In the monsoonal areas, floods seem to become more prevalent during warming trends (e.g. the early Holocene; Kutzbach, 1983). Transitions and phases with frequent events have thus played a major role in shaping the physical and biotic environment during the Holocene.

Strides made in reconstructing past weather and climate

Historical climatology is situated at the interface of climatology and environmental history As such, its goal is to reconstruct weather and climate, as well as natural disasters, for the last millennium prior to the creation of national meteorological networks. Historical climatology is also concerned with investigating the vulnerability of past economies and societies to climate variations, climatic extremes, and natural disasters, and with exploring past discourses and social representations related to climate.