Re-calibration of Arctic sea ice extent datasets using Arctic surface air temperature records

A new seasonal and annual dataset describing Arctic sea ice extents for 1901–2015 was constructed by individually re-calibrating sea ice data sources from the three Arctic regions (North American, Nordic and Siberian) using the corresponding surface air temperature trends for the pre-satellite era (1901–1978), so that the strong relationship between seasonal sea ice extent and surface air temperature observed for the satellite era (1979-present) also applies to the pre-satellite era. According to this new dataset, the recent period of Arctic sea ice retreat since the 1970s followed a period of sea ice growth after the mid-1940s, which in turn followed a period of sea ice retreat after the 1910s. Arctic sea ice is a key component of the Arctic hydrological cycle, through both its freshwater storage role and its influence on oceanic and atmospheric circulation. Therefore, these new insights have significance for our understanding of Arctic hydrology.

EDITOR D. Koutsoyiannis

ASSOCIATE EDITOR not assigned     

Decadal climatic variations recorded in Guliya ice core and comparison with the historical documentary data from East China during the last 2000 years

The high-resolution records of δ¹⁸O and snow accumulation variations from the Guliya ice core provide valuable data for research on climatic variations at a decadal resolution during the past 2000 years in China. Based on the ice core data, five spells have been divided: the warm and wet period before 270 AD, the cold and dry period between 280 and 970 AD, the moderate and dry period between 970 and 1510 AD, the well-defined” Little Ice Age “with drastic cold-warm fluctuations between 1510 and 1930 AD and the warming period since 1930 AD. According to the combination of temperature and precipitation, cold events (55 times) surpass warm ones (26 times), and dry events (55 times) slupass wet ones (45 times). Cold-wet events (14 times) are less than cold-dry ones (16 times), while warm-wet events (10 times) are more than warm-dry ones (4 times). If the difference of2%c in δ¹⁸O (corresponding to 3K in temperature) between two or three adjacent decades is taken as the criterion of it, the abrupt change has taken place 33 times or so since the 3rd century. Among them are four large ones, occurring in 250–280, 550–580, 1220–1260, and 1520–1560 AD respectively. Comparison of the ice core data with the latest comprehensive research results on historical documents of East China shows that the great climatic events appeared simultaneously or at the same age in the ice core record and in the documentary data, suggesting that consistences and similarities in climatic variation among different areas are far away from each other in the lower to mid-latitudes. However, there is a great difference between them during the Medieval Warm Period, which is conspicuous in the historical documents but not in the ice core. In addition, the first cold event of the Little Ice Age on East China was 60 years earlier than that of the Guliya Ice Cap, when the degree of cwling in West China is more intensive than that of East China. But the third cold event in East China lagged behind that in West China during the late 19th century. The 1820s cold event in both West and East China may be caused by the magnificent Tambora volcanic eruption in 1815     

Chronological reconstruction of metal contamination in the Port of Maó (Minorca, Spain)

In this work we discuss the historical record of metals as derived from a sediment core from the Port of Maó (Minorca, Spain), the second natural largest harbour in Europe. The sedimentation rate derived from radionuclide profiles increased by a factor of five since the 1960s due to the urbanisation of the town waterfront. Metal concentrations showed two different trends: (i) Pb and Sn inputs started during the second half of the 19th century and remained relatively high until mid-20th century; and (ii) Ag, Cd, Ni, Zn, Cu and Cr accumulation began in the 1940s, peaking in the late 1970s. The commissioning of a submarine outfall in 1978 reduced metal concentrations in subsequently deposited sediments since, thereafter, urban and industrial wastes have been dumped out of the estuary. This study also shows that evaluating the quality of sediments on the basis of surface concentrations may be misleading.     

Environmental changes reflected by the lake sediments of the South Hongshan Lake, Northwest Tibet

The 1.07-m long lake core with 1 cm interval cutting, which was obtained by drilling in the South Hongshan Lake of Northwest Tibet, was dated by the 210Pb and 137Cs methods, and a 150-year consecutive lake sedimentary sequence (1840─1997) with 1.4 year resolution was obtained. Some environmental proxies, such as the total organic carbon (TOC), total nitrogen (TN), ratio of TOC to TN (TOC/TN), trace chemistry elements (TCE), CaCO3, grain size, richness of ostracoda etc. showed that they are of well coincidence. These results implied that the environmental background varied from the cold-wet period in the late 19th century, to the warm-wet period from the end of the 19th century to the 1920s and to the warm-dry period since the 1920s. There were sub-variations since the 1920s: the cold-dry/warm-wet fluctuation from 1922 to 1960, the intensively warm-dry period since 1960 with a short cold-wet period in the mid-1970s to the end of the 1980s. The humid period from the mid-1970s to the end of the 1970s and the dry period beginning from the early 1980s were well documented by climatic data of the nearby weather station records while the grain size was well correlated to the annual precipitation. Compared with the records from Guliya ice core in the same area, the TOC proxy in the lake core indicating warm/cold conditions well corresponded to the ( 18O records representing temperature variations in the ice core. However, the proxies with dry/wet significance in the lake core were different from the variations of snow accumulation reflected by the ice core. It can be concluded that the chosen environmental proxies have clear environmental significance and the lake sediments can reflect climatic and environmental changes at high-resolution.     

秋季北极海冰与欧亚冬季气温在年代际和年际尺度上的不同联系

北极海冰的急剧消融在近年来欧亚大陆频发的低温事件中扮演着关键角色.秋季北极海冰的偏少对应着冬季欧亚大陆的低温天气,然而二者的联系在年代际和年际两种时间尺度上存在显著区别.本文运用1979—2012年哈德莱中心第一套海冰覆盖率(HadISST1)、欧洲中心(ERA_Interim)的2m温度、风场、海平面气压场、高度场等资料,分别研究了年代际和年际时间尺度上前期秋季北极海冰与欧亚冬季气温的联系.结果表明,欧亚和北极地区(0°—160°E,15°N—90°N)的冬季气温具有显著的年代际和年际变化.在年代际尺度上,温度异常分布在21世纪初由北极冷-大陆暖转为北极暖-大陆冷.这一年代际转折与前期秋季整个北极地区的海冰年代际减少联系密切.秋季北极全区海冰年代际偏少对应冬季欧亚大陆中高纬地区的高压异常,有利于北大西洋的暖湿气流北上和北极的冷空气南侵,造成北极暖-大陆冷的温度分布;在年际时间尺度上,温度异常分布主要由第一模态的年际变化部分和第二模态组成,且第一模态包含的年际变率信号也存在显著的年代际变化.年际尺度上全区北极海冰对欧亚冬季气温的影响远不及位于北冰洋西南边缘的巴伦支海、喀拉海和拉普捷夫海西部(30°E—120°E,75°N—85°N)的关键区海冰影响显著.关键区内海冰的偏少会引发冬季的北大西洋涛动负位相,导致北大西洋吹往欧亚大陆的暖湿气流减弱和欧亚大陆中高纬地区的气温偏低.     

近百年鄱阳湖湿地格局演变研究

鄱阳湖是我国最大淡水湖和长江中游仅存的两个通江湖泊之一,重建其近百年自然通江的湖泊湿地演变过程,对于鄱阳湖湿地生态修复与保护具有重要意义.本研究基于两期历史时期地形图和遥感产品,构建了 1930s、1970s、1990s、2000s和2010s鄱阳湖湿地格局变化数据集,探究了土地利用方式改变和水文连通变化对鄱阳湖湿地变...     

A 200-year precipitation index for the central English Lake District / Un indice de précipitation de 200 ans pour la Région des Lacs en Angleterre

Abstract

Abstract The geographical context and hydroclimatology of the English Lake District means that the region is an important monitor of changes to nationally significant environmental assets. Using monthly rainfall series for sites in and around the central Lake District, a continuous ~200-year precipitation index was constructed for a representative station close to Grasmere. The bridged series shows a significant decline in summer rainfall since the 1960s, offset by increases in winter and spring that are strongly linked to North Atlantic forcing. Over longer time periods, the index exhibits several notable dry (1850s, 1880s, 1890s, 1930s, 1970s) and wet (1820s, 1870s, 1920s, 1940s, 1990s) decades. These patterns are strongly reflected by reservoir inflow series and by indicators of the biological status of the region’s freshwater lakes. It is argued that long-term climate indices will become increasingly important as managers seek to evaluate recent and project environmental changes within the context of long-term natural variability.     

The enrichment characteristics of mercury in the sediments of Dongjiu and Xijiu, Taihu lake catchment, in the past century

The concentration and the enrichment factors of mercury (Hg) in the sediment cores of Dongjiu and Xijiu, Taihu Lake catchment, were studied. The accumulation fluxes, anthropogenic input concentration and anthropogenic accumulation fluxes of Hg in recent 100 years were also analyzed based on the 210Pb dating. The results indicate that the increasing concentrations of Hg in the sediments are influ-enced by natural factors and anthropogenic input simultaneously. Generally, about 2/3 of the Hg in the sediment was from anthropogenic sources. In the early 20th century, the anthropogenic input was owing to the urban development and fossil fuel consumptions surrounding the Taihu Lake and the worldwide atmospheric deposition of Hg since the industrial revolution. The concentration and an-thropogenic fluxes of Hg increased with the industrial development in the catchment since the 1930s. It reached the maximum during the middle 1970s and middle 1990s, and decreased since the middle 1990s with constraints on high pollution industries.     

Chronology of mercury enrichment factors in reef corals from western Venezuela

Mining and deforestation in the early 20th century, the development of petrochemical industries during the 1950s, and the constant weathering of natural deposits of cinabrium (HgS) have made Golfo Triste, Venezuela, a region impacted by mercury (Hg). We studied the chronology of Hg in coral skeletons of Siderastrea siderea (1 colony, 1900-1996) and Montastraea faveolata (2 colonies, 1930-1999) from Parque Nacional San Esteban. Maximum values of Hg/Ca ratios and standard deviations of Hg enrichment factors occurred in the 1940s, 1960s, and 1980s, and matched maxima of decadal rainfall. Values from the 1950s and 1970s matched periods of abundant but constantly decreasing rainfall and hence were best explained by the combination of runoff and the sudden bioavailability of Hg in the region. This sudden availability likely was associated with activities of the chlorine-caustic soda and fertilizer plants of Morón petrochemical complex, industries that started producing large amounts of Hg in 1958.     

Effects of Arctic Sea Ice Decline on Weather and Climate: A Review

The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested large-scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia.     

Cropland cover change in Northeast China during the past 300 years

Land use/cover change induced by human activities has emerged as a “global” phenomenon with Earth system consequences. Northeast China is an area where the largest land cultivation activities by migrants have happened in China during the past 300 years. In this paper, methods including documentary data calibration and multi-sourced data conversion model are used to reconstruct historical cropland cover change in Northeast China during the past 300 years. It is concluded that human beings have remarkably changed the natural landscape of the region by land cultivation in the past 300 years. Cropland area has increased almost exponentially during the past 300 years, especially during the past 100 years when the ratio of cropland cover changed from 10% to 20%. Until the middle of the 19th century, the agricultural area was still mainly restricted in Liaoning Province. From the late 19th century to the early 20th century, dramatic changes took place when the northern boundary of cultivation had extended to the middle of Heilongjiang Province. During the 20th century, three agricultural regions with high ratio of cropland cover were formed after the two phases of spatial expansion of cropland area in 1900s–1930s and 1950s–1980s. Since 1930s–1940s, the expansion of new cultivated area have invaded the forest lands especially in Jilin and Heilongjiang Provinces. Supported by National Natural Science Foundation of China (Grant No. 40571165) and Innovation Foundation of Chinese Academy of Sciences (Grant No. KZCX2-YW-315)     

青藏高原地震活动特征及当前地震活动形势

青藏高原是我国现代构造活动和地震活动最强烈的地区,自有地震记录以来,在高原内记录到多达18次8级以上巨大地震和100余次7~7.9级地震,它们均发生在喜马拉雅板块边界构造带和板内断块区及其次级断块的边界活动构造带上.自1900年有地震仪器记录以来,青藏高原曾经历了3次地震活动丛集高潮,即1920-1937年,1947-1976年和1995-现在.在每次地震活动丛集期都形成以8级地震为核心的7级以上地震活动系列,它们分别是20世纪20-30年代的海原-古浪地震系列、50-70年代察隅-当雄地震系列和20世纪末期以来昆仑-汶川地震系列.每一个地震系列都有自己的主体活动区,最新的昆仑-汶川地震系列的主体活动区为巴颜喀喇断块.青藏高原地震活动高潮与全球M_w≥8.0巨大地震活动高潮紧密相关,昆仑-汶川地震系列与自2001年至今的全球最新地震活动高潮相对应,它们反映了两者的动力学联系.经过详细对比研究认为,它们至今均仍在延续之中,全球板块边界构造带8~9级地震和板内大陆断块区的7~8级地震都仍在连续发生.研究了全球和区域地震活动的相关关系及青藏高原地震活动的时空分布特征,指出了该区当前地震活动的总体形势,评价了其近期地震危险性,提出了加强地震监测的建议.     

Recovery of the early period of long instrumental time series of air temperature in Padua,Italy (1716–2007)

The longest series of instrumental observations have a number of problems in the early period. This paper is focused on the recovery of early indoor and outdoor observations in Padua and their transformation in terms of a modern series. The Padua series was started by Giovanni Poleni with outdoor observations in 1716–1718, but soon, the readings passed indoors (1725–1764) to join the directives of the Royal Society, London. The indoor readings were recovered within the EU project IMPROVE, but it was necessary to transform indoor observations into outdoor ones, and this was possible thanks to the presence of simultaneous indoor and outdoor observations by Morgagni in Padua and Beccari in Bologna. These parallel series were also useful to fill a short gap. Another problem was to reconstruct the calibration of the Amontons thermometer, which changed when Poleni moved to a new house. Also the problem of the use of variable and/or different sampling times was solved making reference to the trend of the daily cycles in the different seasons and under diverse weather conditions. The data analysis has shown a trend that appears similar to the well-known results (IPCC 2007) for the last 160 yr but a less marked recent warming for winter and autumn. The 18th century was characterized by cold winters (culminated 1709 and 1740) and springs, and warm summers and autumns. A well-marked Bruckner cycle (35.8 yr), continually repeated and attenuated, is visible for the period 1716–1930. The wide time scale and the repetition of warmer and colder periods over two-thirds of the series noted in Padua and other Mediterranean stations may induce us to suppose that such cycles could continue in the future, at least on the local scale.     

Spatial and temporal variability of Canadian seasonal precipitation (1900–2000)

Wavelet and cross-wavelet analysis are used to identify and describe spatial and temporal variability in Canadian seasonal precipitation, and to gain further insights into the dynamical relationship between the seasonal precipitation and the dominant modes of climate variability in the Northern Hemisphere. Results from applying continuous wavelet transform to seasonal precipitation series from 201 stations selected from Environment Canada Meteorological Network reveal striking climate-related features before and after the 1940s. The span of available observations, 1900–2000, allows for depicting variance and covariance for periods up to 12 years. Scale-averaged wavelet power spectra are used to simultaneously assess the temporal and spatial variability in each set of 201 seasonal precipitation time series. The most striking feature, in the 2–3-year period and in the 3–6-year period—the 6–12-year period is dominated by white noise and is not considered further—is a net distinction between the timing and intensity of the temporal variability in autumn, winter and spring–summer precipitation. It is found that the autumn season exhibits the most intense activity (or variance) in both the 2–3 year and the 3–6 year periods. The winter season corresponds to the least intense activity for the 2–3 year period, but it exhibits more activity than the spring–summer for the 3–6 year period.Cross-wavelet analysis is provided between the seasonal precipitation and four selected climatic indices: the Pacific North America (PNA), the North Atlantic Oscillation (NAO), the Northern Hemisphere Annular Mode (NAM) originally called the Arctic Oscillation, and the sea surface temperature series over the Niño-3 region (ENSO). The wavelet cross-spectra revealed coherent space–time variability of the climate–precipitation relationship throughout Canada. It is shown that strong climate/precipitation activity (or covariance) in the 2–6 year period starts after 1940 whatever the climatic index and the season. Prior to year 1940, only local and weaker 2–6 year activity is revealed in western Canada essentially in winter and autumn, but overall a non-significant precipitation/climate relationship is observed prior to 1940. Correlation analysis in the 2–6 year band between the seasonal precipitation and the selected climatic indices revealed strong positive correlations with the ENSO, the NAO, and the NAM in eastern and western Canada for the post-1940 period. For the period prior to 1940, the correlation tend be negative for all the indices whatever the region. A particular feature in the correlation analysis results is the consistently stronger and positive NAM–precipitation correlations in all the regions since 1940. The cross-wavelet spectra and the correlation analysis in the 2–6 year band suggest the presence of a change point around 1940 in Canadian seasonal precipitation—that is found to be more likely related to NAM dynamics.     

Climatic and environmental changes over the last millennium recorded in the Malan ice core from the northern Tibetan Plateau

In this paper, climatic and environmental changes were reconstructed since 1129A.D. based on the Malan ice core from Hol Xil, the northern Tibetan Plateau. The record of δ 18O in the Malan ice core indicated that the warm-season air temperature variations displayed a general increase trend, the 20th-century warming was within the range of natural climate variability, and the warmest century was the 17th century while the warmest decade was the 1610s, over the entire study period. The “Medieval Warm Epoch” and “Little Ice Age” were also reflected by the ice core record. The dust ratio in the Malan ice core is a good proxy for dust event frequency. The 870-year record of the dust ratio showed that dust events occurred much frequently in the 19th century. Comparing the variations of δ 18O and the dust ratio, it is found that there was a strong negative correlation between them on the time scales of 101―102 years. By analyses of all the climatic records of ice cores and tree rings from the northern Tibetan Plateau, it was revealed that dust events were more frequent in the cold and dry periods than in the warm and wet periods.     

The chronology and the hydrometeorology of catastrophic floods on Dartmoor,South West England

Extreme floods are the most widespread and often the most fatal type of natural hazard experienced in Europe, particularly in upland and mountainous areas. These ‘flash flood’ type events are particularly dangerous because extreme rainfall totals in a short space of time can lead to very high flow velocities and little or no time for flood warning. Given the danger posed by extreme floods, there are concerns that catastrophic hydrometeorological events could become more frequent in a warming world. However, analysis of longer term flood frequency is often limited by the use of short instrumental flow records (last 30–40 years) that do not adequately cover alternating flood‐rich and flood‐poor periods over the last 2 to 3 centuries. In contrast, this research extends the upland flood series of South West England (Dartmoor) back to ca AD 1800 using lichenometry. Results show that the period 1820 to mid‐1940s was characterized by widespread flooding, with particularly large and frequent events in the mid‐to‐late 19th and early 20th centuries. Since ca 1850 to 1900, there has been a general decline in flood magnitude that was particularly marked after the 1930s/mid‐1940s. Local meteorological records show that: (1) historical flood‐rich periods on Dartmoor were associated with high annual, seasonal and daily rainfall totals in the last quarter of the 19th century and between 1910 and 1946, related to sub‐decadal variability of the North Atlantic Oscillation and receipt of cyclonic and southerly weather types over the southwest peninsula; and (2) the incidence of heavy daily rainfall declined notably after 1946, similar to sedimentary archives of flooding. The peak period of flooding on Dartmoor predates the beginning of gauged flow records, which has practical implications for understanding and managing flood risk on rivers that drain Dartmoor. Copyright © 2013 John Wiley & Sons, Ltd.     

Magnetic field measurements in India during the last two centuries

Summary The direction of the geomagnetic field has changed substantially less in India than in Europe since the end of the 18th century.Whereas the European geomagnetic time series indicate a tendency of secular variation from which a remarkable westward drift of the non-axial field can be deduced, in India the field direction seems to have remained more or less fixed over the last two centuries. The drift of the non-axial field seems to be very small, or even eastward.     

Increasing discharge from the Mackenzie River system to the Arctic Ocean

The Mackenzie River, Canada's longest and largest river system, provides the greatest Western Hemisphere discharge to the Arctic Ocean. Recent reports of declining flows have prompted concern because (1) this influences Arctic Ocean salinity, stratification and polar ice; (2) a major tributary, the Peace River, has large hydroelectric projects, and further dams are proposed; and (3) the system includes the extensive and biodiverse Peace–Athabasca, Slave and Mackenzie deltas. To assess hydrological trends over the past century that could reflect climate change, we analysed historic patterns of river discharges. We expanded the data series by infilling for short gaps, calculating annual discharges from early summer‐only records (typical r² > 0.9), coordinating data from sequential hydrometric gauges (requiring r² > 0.8) and advancing the data to 2013. For trend detection, Pearson correlation provided similar outcomes to non‐parametric Kendall's τ and Spearman's ρ tests. There was no overall pattern for annual flows of the most southerly Athabasca River (1913–2013), while the adjacent, regulated Peace River displayed increasing flows (1916–2013, p < 0.05). These rivers combine to form the Slave River, which did not display an overall trend (1917–2013). The more northerly, free‐flowing Liard River is the largest tributary and displayed increasing annual flows (1944–2013, p < 0.01, ~3.5% per decade) because of increasing winter, spring, and summer flows, and annual maximum and minimum flows also increased. Following from the tributary contributions, the Mackenzie River flows gradually increased (Fort Simpson 1939–2013, p < 0.05, ~1.5% per decade), but the interannual patterns for the Liard and other rivers were correlated with the Pacific Decadal Oscillation, complicating the pattern. This conclusion of increasing river flows to the Arctic Ocean contrasts with some prior reports, based on shorter time series. The observed flow increase is consistent with increasing discharges of the large Eurasian Arctic drainages, suggesting a common northern response to climate change. Analyses of historic trends are strengthened with lengthening records, and with the Pacific Decadal Oscillation influence, we recommend century‐long records for northern rivers. Copyright © 2016 John Wiley & Sons, Ltd.     

Current state of heterotrophic bacterioplankton in the Kosinskie Lakes

From December 2009 to December 2010, the total abundance of bacteria, the abundance of bacteria with electron transport chain, the abundance of viable saprotrophic bacteria, and the concentration of chlorophyll a were studied in water samples from lakes Svyatoe, Beloe, and Chernoe in Kosino-Ukhtomskoe district, Moscow City. The abundance of bacteria with active electron transport chain (CTC+bacteria) and its seasonal variations in Kosinskie Lakes are studied for the first time. Those lakes were found to contain well-developed and actively functioning heterotrophic bacterioplankton, the abundance of which have increased considerably since the 1930s–1940s. The seasonal dynamics of bacterioplankton has also changed. The largest absolute abundance of CTC+bacteria in lakes Svyatoe and Beloe was recorded in summer and autumn (from August to November). The abundance peak of CTH+bacteria in Lake Svyatoe was recorded in September and that in Lake Beloe, in October. The abundance of CTC+bacteria also showed a peak in April. In Lake Chernoe, the abundance of CTC+bacteria was much less than in lakes Svyatoe and Beloe; its maximums were recorded in December 2009 and April 2010. The share of CTC+bacteria in the total abundance of bacteria was 2.4–19.2% in Lake Svyatoe, 1.8–63.0% in Lake Beloe, and 0.96–22.5% in Lake Chernoe. Significant correlations were found to exist in all three lakes between the abundance of active bacterioplankton fraction and chlorophyll a content of water.     

Hydro-climatology of the Lower Rhône Valley: historical flood reconstruction (AD 1300–2000) based on documentary and instrumental sources

From the HISTRHONE database we extracted 1483 hydro-meteorological events from AD 1300 to 2000 that occurred in the Lower Rhône Valley, France. Daily heights of the Rhône River at Beaucaire and Arles are also available, from 1816 and 1829, respectively. A total of 517 floods were divided into three categories and a synthetic frequency severity index (FSI) was computed. Running averages of 11 and 31 years show a succession of poor and rich flood fluctuations. Extreme floods tripled in the second half of the period (1650–2000). Singular spectrum analysis isolates a dominant irregular component (main positive anomalies in 1450–1580, around 1700, late 18th century, and most of the 20th century). We focus on the 17th century, with rare flooding events between two secular so-called “hyper phases”, i.e. frequent and/or severe floods. We also recorded 173 episodes of ice in the river, during the Little Ice Age.