scholarly journals Long-term changes of the ice regime of rivers in Latvia

2016 ◽  
Vol 47 (4) ◽  
pp. 782-798
Author(s):  
Inese Latkovska ◽  
Elga Apsīte ◽  
Didzis Elferts
Keyword(s):  
Regional Differences ◽  
Severity Index ◽  
Ice Cover ◽  
Ice Thickness ◽  
Positive Trend ◽  
The West ◽  
Climate Conditions ◽  
Long Term Changes ◽  
Ice Regime

The ice regime of rivers is considered a sensitive indicator of climate change. This paper summarises the results of research on the long-term changes in the ice regime parameters under changing climate conditions and their regional peculiarities in Latvia from 1945 to 2012. The ice cover duration on Latvian rivers has decreased during recent decades. The research results demonstrated that there is a positive trend as regards the formation of the ice cover and in 31.8% of the cases the trend is statistically significant at p < 0.05. As regards the breaking up of ice, there is a statistically significant negative trend in 93.2% of the cases at p < 0.05. This indicates an earlier ice break-up date, which in turn, displays a strong correlation with the increase of the air temperature. The same pattern applies to the reduction of the length of ice cover (a statistically significant trend in 86.4% of the cases at p < 0.05). In approximately 60% of the cases, there is a statistically significant reduction of the ice thickness. The estimated winter severity index indicates warmer winters over the last 20 years as well as regional differences in the west–east direction.

scholarly journals Variability and past long-term changes of brominated very short-lived substances at the tropical tropopause

2020 ◽  
Vol 20 (11) ◽  
pp. 7103-7123
Author(s):  
Susann Tegtmeier ◽  
Elliot Atlas ◽  
Birgit Quack ◽  
Franziska Ziska ◽  
Kirstin Krüger
Keyword(s):  
Central America ◽  
Temporal Variability ◽  
Spatial And Temporal Variability ◽  
Positive Trend ◽  
The West ◽  
West Pacific ◽  
Mixing Ratios ◽  
Long Term Changes ◽  
Averaged Model

Abstract. Halogenated very short-lived substances (VSLSs), such as bromoform (CHBr3), can be transported to the stratosphere and contribute to the halogen loading and ozone depletion. Given their highly variable emission rates and their short atmospheric lifetimes, the exact amount as well as the spatio-temporal variability of their contribution to the stratospheric halogen loading are still uncertain. We combine observational data sets with Lagrangian atmospheric modelling in order to analyse the spatial and temporal variability of the CHBr3 injection into the stratosphere for the time period 1979–2013. Regional maxima with mixing ratios of up to 0.4–0.5 ppt at 17 km altitude are diagnosed to be over Central America (1) and over the Maritime Continent–west Pacific (2), both of which are confirmed by high-altitude aircraft campaigns. The CHBr3 maximum over Central America is caused by the co-occurrence of convectively driven short transport timescales and strong regional sources, which in conjunction drive the seasonality of CHBr3 injection. Model results at a daily resolution reveal isolated, exceptionally high CHBr3 values in this region which are confirmed by aircraft measurements during the ACCENT campaign and do not occur in spatially or temporally averaged model fields. CHBr3 injection over the west Pacific is centred south of the Equator due to strong oceanic sources underneath prescribed by the here-applied bottom-up emission inventory. The globally largest CHBr3 mixing ratios at the cold point level of up to 0.6 ppt are diagnosed to occur over the region of India, Bay of Bengal, and Arabian Sea (3); however, no data from aircraft campaigns are available to confirm this finding. Inter-annual variability of stratospheric CHBr3 injection of 10 %–20 % is to a large part driven by the variability of coupled ocean–atmosphere circulation systems. Long-term changes, on the other hand, correlate with the regional sea surface temperature trends resulting in positive trends of stratospheric CHBr3 injection over the west Pacific and Asian monsoon region and negative trends over the east Pacific. For the tropical mean, these opposite regional trends balance each other out, resulting in a relatively weak positive trend of 0.017±0.012 ppt Br per decade for 1979–2013, corresponding to 3 % Br per decade. The overall contribution of CHBr3 together with CH2Br2 to the stratospheric halogen loading accounts for 4.7 ppt Br, in good agreement with existing studies, with 50 % and 50 % being injected in the form of source and product gases, respectively.

scholarly journals Variability and long-term changes of brominated VSLS at the tropical tropopause

2019 ◽  
Author(s):  
Susann Tegtmeier ◽  
Elliot Atlas ◽  
Birgit Quack ◽  
Franziska Ziska ◽  
Kirstin Krüger
Keyword(s):  
Central America ◽  
Spatial And Temporal Variability ◽  
Positive Trend ◽  
The West ◽  
Asian Monsoon Region ◽  
West Pacific ◽  
Mixing Ratios ◽  
Long Term Changes ◽  
Averaged Model

Abstract. We combine available observational data sets with Lagrangian atmospheric modelling in order to analyze the spatial and temporal variability of the CHBr3 injection into the stratosphere. Regional maxima with mixing ratios of up to 0.4–0.5 ppt at 17 km altitude are diagnosed to be over Central America (1) and over the Maritime Continent/West Pacific (2), both of which are confirmed by high-altitude aircraft campaigns. The CHBr3 maximum over Central America is caused by the co-occurrence of convectively-driven short transport time scales and strong regional sources, which in conjunction drive the seasonality of CHBr3 injection. Model results at a daily resolution reveal isolated, exceptionally high CHBr3 values in this region which are confirmed by measurements during the ACCENT campaign and do not occur in spatially or temporally averaged model fields. CHBr3 injection over the West Pacific is centered south of the equator due to strong oceanic sources underneath prescribed by the here applied bottom-up emission inventory. The globally strongest stratospheric CHBr3 injection of up to 0.6 ppt is diagnosed to occur over the region of India, Bay of Bengal and Arabian Sea (3), however, no data from aircraft campaigns are available to confirm this finding. Interannual variability of stratospheric CHBr3 injection of 10–20 % is to a large part driven by the variability of coupled ocean-atmosphere circulation systems. Long-term changes, on the other hand, correlate with the regional SST trends resulting in positive trends of stratospheric CHBr3 injection over the West Pacific and Asian monsoon region and negative trends over the East Pacific. For the tropical mean, these opposite regional trends balance each other out resulting in a relatively weak positive trend of 0.017 ± 0.012 ppt Br/dec for 1979–2013, corresponding 3 % Br/dec. The overall contribution of CHBr3 together with CH2Br2 to the stratospheric halogen loading accounts for 4.7 ppt Br, in good agreement with existing studies, with 50 %/50 % being injected in form of source and product gases, respectively.

Long-term changes in lake ice cover in Finland*

2006 ◽  
Vol 37 (4-5) ◽  
pp. 347-363 ◽  
Author(s):  
Johanna Korhonen
Keyword(s):  
Time Series ◽  
19Th Century ◽  
Ice Cover ◽  
Ice Thickness ◽  
Lake Ice ◽  
Early 19Th Century ◽  
Long Term Changes ◽  
Break Up ◽  
Thickness Measurements

The freeze-up and break-up records of almost ninety lakes, and ice thickness of about thirty lakes, were analysed in order to identify long-term changes in the ice regime in Finland. The longest time series of break-up and freeze-up of ice in lakes are available from the early 19th century, while the earliest ice thickness measurements started in the 1910s. The analysis showed that there is a significant change towards earlier ice break-up in Finland except in the very north from the late 19th century to the present time. There is also a significant trend towards later freeze-up and thus also towards a shorter ice cover duration for the longest time series. However, for most lakes, for which data are not available prior to 1900, there are no significant trends. The ice thickness seems to have increased over the last 40 years, although there are significant trends only in half of the investigated lakes and significant decrease in the maximum ice thickness was found in four lakes in southern Finland. The increased ice thickness is most likely due to heavy snow on the ice and production of snow ice.

Long-term changes in hydrological regime of the lakes in Latvia

2013 ◽  
Vol 45 (3) ◽  
pp. 308-321 ◽  
Author(s):  
Elga Apsīte ◽  
Didzis Elferts ◽  
Andrejs Zubaničs ◽  
Inese Latkovska
Keyword(s):  
Surface Water ◽  
Water Level ◽  
Global Climate ◽  
Hydrological Regime ◽  
Positive Trend ◽  
Surface Water Temperature ◽  
Global Climate Warming ◽  
Long Term Changes ◽  
Ice Regime

Changes in the hydrological regime of the lakes of Latvia depend on natural and anthropogenic causes. This publication summarises the results of the research on the long-term changes in the water level, thermal and ice regimes in the seven largest lakes of Latvia: Liepājas, Usma, Ķīšezers, Burtnieks, Rāzna, Sventes and Lielais Ludzas, and their regional specifics from 1926 to 2002. For most of the studied lakes, the water level has been regulated, except for the lakes Liepājas, Burtnieks and Ķīšezers. Global climate warming has caused considerable changes in the hydrological regime of the lakes during the last decades and the surface water temperature has increased. At the same time, the number of days with ice cover and the thickness of ice have decreased. A positive trend in the freezing date and a statistically significant negative trend for the ice break-up date was found for all lakes. The lakes Liepājas and Usma are located in the western part and Lake Kīšezers in the central part, therefore their hydrological regime, in particular, the thermal and ice regime, differs from the lakes Burtnieks, Rāznas, Sventes and Lielais Ludzas which are located in the northern and south-eastern part of Latvia.

scholarly journals Dynamics of the ice regime of the Sea of Azov in the XX–XXI centuries

2018 ◽  
Vol 58 (3) ◽  
pp. 373-386 ◽  
Author(s):  
N. V. Yaitskaya ◽  
A. A. Magaeva
Keyword(s):  
Ice Cover ◽  
Sea Surface ◽  
Sea Of Azov ◽  
The Sea Of Azov ◽  
Azov Sea ◽  
Fast Ice ◽  
Ice Regime ◽  
Degree Of Severity ◽  
Ice Period

The ice regime of the Sea of Azov over the period of 20th and 21nd centuries was investigated using the author's GIS «The ice regime of the Southern Seas of the Russia». The long-term dynamics of the ice cover, duration of the ice stay as well as beginning and end of the ice period were considered. It has been found that for the period of 1950–2015 the average annual value of the Azov Sea ice cover area is 33%, while the average area of the fast ice is 6.3% of the total area of the sea. Value of duration of the ice cover stay on the sea surface has been refined, and this value is 115 days near the hydro-meteorological station (HMS) Taganrog and 63 days near the HMS Kerch. The typification of winters according to the degree of severity was performed on the basis of data from three coastal meteorological stations: Taganrog, Genichesk, and Kerch. Winters of moderate type were shown to be prevailing during the entire analyzed period. Totally, 15 severe, 70 moderate and 40 mild winters were isolated for the period 1883-2015, while for 1950–2015 the statistics was the following: 9 severe, 43 moderate, and 14 mild winters in Taganrog, and 10 severe, 40 moderate, and 16 mild winters in Kerch.

scholarly journals Long-Term Variability in the Course of Ice Phenomena on the Vistula River in Toruń

2009 ◽  
Vol 1 (1) ◽  
pp. 91-102 ◽  
Author(s):  
Bogusław Pawłowski
Keyword(s):  
Water Management ◽  
Middle Ages ◽  
Ice Cover ◽  
Data Series ◽  
Vistula River ◽  
Winter Temperatures ◽  
Ice Regime ◽  
River Control ◽  
Ice Phenomena

Abstract Our first information of ice cover on the Vistula River in Poland dates from the Middle Ages. However, only since the 19th century have continuous observations been available. This study makes use of a data series, obtained mainly from IMGW (Institute of Meteorology and Water Management), covering the years 1861-2003 for ice phenomena and 1814-2003 for ice cover. Considerable shortening has been observed in the duration of both ice phenomena (from 60-120 days to 30-80 days) and ice cover (from 40-100 days to 20-60 days). These trends correspond well with the trend in winter temperatures becoming warmer. However, the transformation of the ice regime on the Vistula River in Toruń has also been affected by the river control, the construction and operation of the Włocławek Dam and (to a lesser degree than at Korzeniewo) icebreaking activities.

scholarly journals Evidence of recent changes in the ice regime of lakes in the Canadian High Arctic from spaceborne satellite observations

2015 ◽  
Vol 9 (6) ◽  
pp. 6223-6274
Author(s):  
C. M. Surdu ◽  
C. R. Duguay ◽  
D. Fernández Prieto
Keyword(s):  
Ice Cover ◽  
High Arctic ◽  
Arctic Lakes ◽  
Climate Conditions ◽  
Polar Desert ◽  
Growing Seasons ◽  
Surface Areas ◽  
Key Indicator ◽  
Ice Regime ◽  
Wide Swath

Abstract. Arctic lakes, through their ice cover phenology, are a key indicator of climatic changes that the high-latitude environment is experiencing. In the case of lakes in the Canadian Arctic Archipelago (CAA), many of which are ice covered more than ten months per year, warmer temperatures could result in ice regime shifts. Within the dominant polar-desert environment, small local warmer areas have been identified. These relatively small regions – polar oases – with longer growing seasons, greater biological production and diversity, are confined from the surrounding barren polar desert. The ice regimes of 11 lakes located in both polar-desert and polar-oasis environments, with surface areas between 4 and 542 km2, many of unknown bathymetry, were documented. In order to investigate the response of ice cover of lakes in the CAA to climate conditions during recent years, a 15-year time series (1997–2011) of RADARSAT-1/2 ScanSAR Wide Swath, ASAR Wide Swath and Landsat acquisitions were analysed. Results show that melt onset (MO) occurred earlier for all observed lakes. With the exception of Lower Murray Lake, all lakes experienced earlier summer-ice minimum and water-clear-of-ice dates (WCI), with greater changes being observed for polar-oasis lakes (9–24 days earlier WCI dates for lakes located in polar oases and 2–20 days earlier WCI dates for polar-desert lakes). Additionally, results suggest that some lakes may be transitioning from a perennial/multiyear to a seasonal ice regime, with only a few lakes maintaining a multiyear ice cover on occasional years. Aside Lake Hazen and Murray Lakes that preserved their ice cover during the summer of 2009, no residual ice was observed on any of the other lakes from 2007 to 2011.

scholarly journals Long-term changes in regional vegetation cover along the west coast of southern Norway: The importance of human impact

2018 ◽  
Vol 29 (3) ◽  
pp. 404-415 ◽  
Author(s):  
Kari Loe Hjelle ◽  
Lene S. Halvorsen ◽  
Lisbeth Prøsch-Danielsen ◽  
Shinya Sugita ◽  
Aage Paus ◽  
...  
Keyword(s):  
Human Impact ◽  
West Coast ◽  
Vegetation Cover ◽  
The West ◽  
Long Term Changes ◽  
Southern Norway

scholarly journals Long-Term Changes in Hydrological Regime of the Lakes Usma, Burtnieks and Rāzna

2012 ◽  
Vol 66 (6) ◽  
pp. 261-270
Author(s):  
Elga Apsīte ◽  
Mārtiņš Kriķītis ◽  
Inese Latkovska ◽  
Andrejs Zubaničs
Keyword(s):  
Water Level ◽  
Global Climate ◽  
Hydrological Regime ◽  
Positive Trend ◽  
Global Climate Warming ◽  
Regional Features ◽  
Natural Factors ◽  
Ice Regime ◽  
The Impact

Changes in the hydrological regime of the lakes of Latvia have been caused by several natural and human factors. This publication summarises the results of research on the long-term and seasonal changes in the water level, and thermal and ice regimes of the three biggest lakes of Latvia (Usma, Burtnieks, and Râzna) and their regional features in the period from 1926 to 2002. The levels of the lakes Usma and Râzna have been controlled, but it can be considered that changes of the water level in Lake Burtnieks have been due to the impact of natural factors during the period from 1947 to 2002. Global climate warming has caused considerable changes in the hydrological regime of the lakes during the last decades, as the water level and temperature have increased and the number of days with ice cover and the thickness of ice have decreased. A positive trend in the freezing data and statistically reliable negative trend for the ice break-up date were observed for all the lakes. Lake Usma is located in the western part of Latvia, therefore, its hydrological regime, in particular, the thermal and ice regime, differs from those of lakes Burtnieks and Râzna which are located in the northern and eastern part of Latvia, respectively.

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