scholarly journals The influence of river ice on spring runoff in the Lena river, Siberia

2005 ◽  
Vol 40 ◽  
pp. 123-127 ◽  
Author(s):  
Xieyao Ma ◽  
Tetsuzo Yasunari ◽  
Tetsuo Ohata ◽  
Yoshihiro Fukushima

AbstractThe Lena river is one of the four largest rivers flowing into the Arctic Ocean. It has a complicated hydrological system that is affected not only by the amount of precipitation but also by the timing of ice break-up. To determine the mechanisms of runoff formation, a numerical analysis based on modeling was carried out for the period 1986–2000. The results show that (1) the timing of flood rise and peak can be modeled at Tabaga, which represents the upper and central portions of the Lena river; (2) river-freeze processes delay the spring, snowmelt-dominated flood by about 23 days; and (3) the difference between the break-up dates at Tabaga and Kirensk has ranged from several days to >2 months, and a maximum value of 69 days was recorded in spring 1998.

2011 ◽  
Vol 8 (2) ◽  
pp. 2093-2143 ◽  
Author(s):  
I. P. Semiletov ◽  
I. I. Pipko ◽  
N. E. Shakhova ◽  
O. V. Dudarev ◽  
S. P. Pugach ◽  
...  

Abstract. The Lena River integrates biogeochemical signals from its vast drainage basin and its signal reaches far out over the Arctic Ocean. Transformation of riverine organic carbon into mineral carbon, and mineral carbon into the organic form in the Lena River watershed, can be considered a quasi-equilibrated processes. Increasing the Lena discharge causes opposite effects on total organic (TOC) and inorganic (TCO2) carbon: TOC concentration increases, while TCO2 concentration decreases. Significant inter-annual variability in mean values of TCO2, TOC, and their sum (TC) has been found. This variability is determined by changes in land hydrology which cause differences in the Lena River discharge, because a negative correlation may be found between TC in September and mean discharge in August (a time shift of about one month is required for water to travel from Yakutsk to the Laptev Sea). Total carbon entering the sea with the Lena discharge is estimated to be almost 10 Tg C y−1. The annual Lena River discharge of particulate organic carbon (POC) may be equal to 0.38 Tg (moderate to high estimate). If we instead accept Lisytsin's (1994) statement concerning the precipitation of 85–95% of total particulate matter (PM) (and POC) on the marginal "filter", then only about 0.03–0.04 Tg of POC reaches the Laptev Sea from the Lena River. The Lena's POC export would then be two orders of magnitude less than the annual input of eroded terrestrial carbon onto the shelf of the Laptev and East Siberian seas, which is about 4 Tg. The Lena River is characterized by relatively high concentrations of primary greenhouse gases: CO2 and dissolved CH4. During all seasons the river is supersaturated in CO2 compared to the atmosphere: up to 1.5–2 fold in summer, and 4–5 fold in winter. This results in a narrow zone of significant CO2 supersaturation in the adjacent coastal sea. Spots of dissolved CH4 in the Lena delta channels may reach 100 nM, but the CH4 concentration decreases to 5–20 nM towards the sea, which suggests only a minor role of riverborne export of CH4 for the East Siberian Arctic Shelf (ESAS) CH4 budget in coastal waters. Instead, the seabed appears to be the source that provides most of the CH4 to the Arctic Ocean.


2018 ◽  
Vol 241 ◽  
pp. 120-133 ◽  
Author(s):  
Xiaole Sun ◽  
Carl-Magnus Mörth ◽  
Don Porcelli ◽  
Liselott Kutscher ◽  
Catherine Hirst ◽  
...  

2021 ◽  
Author(s):  
Bennet Juhls ◽  
Anne Morgenstern ◽  
Pier Paul Overduin

<p>River biogeochemistry at any location integrates environmental processes over a definable upstream area of the river watershed. Therefore, biogeochemical parameters of river water are powerful indicators of the climate change impact on the entire watershed and smaller parts of it.</p><p>The current warming of the Siberian Arctic is changing atmospheric forcing, precipitation, subsurface water storage, and runoff from rivers to the Arctic Ocean. A number of studies predict an increase of organic carbon export by rivers into the Arctic Ocean with further warming of the Arctic. Major potential drivers for this increase are the rise of river discharge and permafrost thaw, which mobilizes organic matter.</p><p>Here, we present results of high frequency monitoring program of the Lena River waters in the central part of its delta at the Laptev Sea. For the first time, a number of biogeochemical parameters such as dissolved organic carbon (DOC), coloured dissolved organic matter, electrical conductivity, temperature, and d<sup>18</sup>O isotopes were measured at an interval of every few days throughout the entire season. Currently, the data set comprises two complete years from the spring 2018 until the spring 2020, which were characterized by extremely high and low summer discharges, respectively. While 2018 to 2019 was the fourth highest on record from 1936 to present, resulting in an annual DOC flux of 6.8 Tg C yr<sup>-1</sup>, 2019 was the sixth lowest discharge year with a significantly lower DOC flux of 4.5 Tg C yr<sup>-1</sup>. Endmember analysis using electrical conductivity and d<sup>18</sup>O isotopes showed that rainwater transported less DOC in 2019 (1.5 Tg C) than in 2018 (2.9 Tg C) although the winter base flow and the snow and ice meltwater transported similar amounts.</p><p>The biogeochemical response of the Lena River water provides us with new insights into the catchment processes, including permafrost thaw and potential mobilization of previously frozen organic carbon. Our new monitoring program will serve 1) as a baseline to measure future changes and 2) as a training dataset to project changes under future climate scenarios.</p>


2019 ◽  
Vol 16 (11) ◽  
pp. 2343-2367 ◽  
Author(s):  
Jens Terhaar ◽  
James C. Orr ◽  
Marion Gehlen ◽  
Christian Ethé ◽  
Laurent Bopp

Abstract. The Arctic Ocean is projected to experience not only amplified climate change but also amplified ocean acidification. Modeling future acidification depends on our ability to simulate baseline conditions and changes over the industrial era. Such centennial-scale changes require a global model to account for exchange between the Arctic and surrounding regions. Yet the coarse resolution of typical global models may poorly resolve that exchange as well as critical features of Arctic Ocean circulation. Here we assess how simulations of Arctic Ocean storage of anthropogenic carbon (Cant), the main driver of open-ocean acidification, differ when moving from coarse to eddy-admitting resolution in a global ocean-circulation–biogeochemistry model (Nucleus for European Modeling of the Ocean, NEMO; Pelagic Interactions Scheme for Carbon and Ecosystem Studies, PISCES). The Arctic's regional storage of Cant is enhanced as model resolution increases. While the coarse-resolution model configuration ORCA2 (2∘) stores 2.0 Pg C in the Arctic Ocean between 1765 and 2005, the eddy-admitting versions ORCA05 and ORCA025 (1∕2∘ and 1∕4∘) store 2.4 and 2.6 Pg C. The difference in inventory between model resolutions that is accounted for is only from their divergence after 1958, when ORCA2 and ORCA025 were initialized with output from the intermediate-resolution configuration (ORCA05). The difference would have been larger had all model resolutions been initialized in 1765 as was ORCA05. The ORCA025 Arctic Cant storage estimate of 2.6 Pg C should be considered a lower limit because that model generally underestimates observed CFC-12 concentrations. It reinforces the lower limit from a previous data-based approach (2.5 to 3.3 Pg C). Independent of model resolution, there was roughly 3 times as much Cant that entered the Arctic Ocean through lateral transport than via the flux of CO2 across the air–sea interface. Wider comparison to nine earth system models that participated in the Coupled Model Intercomparison Project Phase 5 (CMIP5) reveals much larger diversity of stored Cant and lateral transport. Only the CMIP5 models with higher lateral transport obtain Cant inventories that are close to the data-based estimates. Increasing resolution also enhances acidification, e.g., with greater shoaling of the Arctic's average depth of the aragonite saturation horizon during 1960–2012, from 50 m in ORCA2 to 210 m in ORCA025. Even higher model resolution would likely further improve such estimates, but its prohibitive costs also call for other more practical avenues for improvement, e.g., through model nesting, addition of coastal processes, and refinement of subgrid-scale parameterizations.


2020 ◽  
Author(s):  
Bennet Juhls ◽  
Pier Paul Overduin ◽  
Colin Andrew Stedmon ◽  
Anne Morgenstern ◽  
Hanno Meyer ◽  
...  

<p>The carbon export by rivers to the Arctic Ocean is expected to increase in response to the rapidly changing climate in the Arctic (Camill, 2005; Freeman et al., 2001; Frey and Smith, 2005). This is in part due to thawing permafrost and mobilization of particulate and dissolved organic matter (DOM). The Lena River delivers approximately one fifth of the total river discharge to the Arctic Ocean and is the main source of DOM in the Laptev Sea shelf (Thibodeau et al., 2014). To date river fluxes of DOM have been based on sparse coverage of sample across the hydrograph about 700 km upstream (Cooper et al 2005; Raymond et al 2007; Stedmon et al 2011; Amon et al 2012). The effects of low frequency sampling on load estimates are unknown and potentially large for systems such as these where there are considerable changes across the hydrograph.   Here we present results from a unique high frequency sampling program and evaluate its viability to monitor export fluxes of DOM and its biogeochemistry in the Lena River. The sampling takes place close to the river mouth at the research station Samoylov in the central Lena River Delta. The Samoylov research station allows a unique chance for continuous sampling since it operates throughout the year. The sampling program includes measurements of several water parameters, such as temperature, electric conductivity, dissolved organic carbon (DOC), spectral CDOM absorption (aCDOM), fluorescent dissolved organic matter (FDOM) and water stable isotopes.<br>The data facilitated the identification of the main drivers behind the seasonality of DOM concentration and biogeochemistry of the Lena River. Three main water sources could be identified (1) (snow) melt water, (2) rain water and (3) subsurface water. Melt and rain water are found to be the prevailing water sources that combined transport 5.8 Tg C dissolved organic matter (~ 85 % of annual flux (6.8 Tg C)) into the Lena River. The high number of samples throughout the whole year allowed flux calculations that are independently from load models that likely lead to a large variation of earlier studies.<br>The absorption properties of DOM revealed changing composition and sources of DOM throughout the year. Decreasing SUVA values during the summer point towards an increasing fraction of old DOM which potentially originates from degrading permafrost. In contrast, during the spring freshet, high SUVA indicate mostly fresh organic matter with high molecular weight and high aromaticity.<br>This dataset represents the first year of a planned long-term monitoring program at the Research Station Samoylov Island and provides a baseline data set against which future change of this large integrative system may be measured. A continuous sampling of Arctic River water will facilitate to identify intra and inter-annual trends with ongoing climate change.</p>


2020 ◽  
Author(s):  
Van Liem Nguyen ◽  
Birgit Wild ◽  
Örjan Gustafsson ◽  
Igor Semiletov ◽  
Oleg Dudarev ◽  
...  

<p>Widespread accelerated permafrost thawing is predicted for this century and beyond. This threatens to remobilize the large amounts of Mercury (Hg) currently ‘locked’ in Arctic permafrost soils to the Arctic Ocean and thus potentially lead to severe consequences for human and wildlife health. Future risks of Arctic Hg in a warmer climate are, however, poorly understood. One crucial knowledge gap to fill is the fate of Hg once it enters the marine environment on the continental shelves. Arctic rivers are already today suggested to be the main source of Hg into the Arctic Ocean, with dissolved and particulate organic matter (DOM and POM, respectively) identified as important vectors for the land to sea transport.</p><p>In this study, we have investigated total Hg (HgT) and monomethylmercury (MeHg) concentrations in surface sediments from the East Siberian Arctic Shelf (ESAS) along a transect from the Lena river delta to the Laptev Sea continental slope. The ESAS is the world’s largest continental shelf and receives large amounts of organic carbon by the great Arctic Russian rivers (e.g., Lena, Indigirka and Kolyma), remobilized from continuous and discontinuous permafrost regions in the river catchments, and from coastal erosion. Data on HgT and MeHg levels in ESAS sediments is however limited. Here, we observed concentrations of Hg ranging from 30 to 96 ng Hg g<sup>-1</sup> d.w. of HgT, and 0.03 to 9.5 ng Hg g<sup>-1</sup> d.w. of MeHg. Similar concentrations of HgT were observed close to the river delta (54 ± 19 ng Hg g<sup>-1</sup> d.w.), where >95 % of the organic matter is of terrestrial origin, and the other section of the transect (42 ± 7 ng Hg g<sup>-1</sup> d.w.) where the terrestrial organic matter is diluted with carbon from marine sources. In contrast, we observed higher concentrations of MeHg close to the river delta (0.72 ± 0.71 ng Hg g<sup>-1</sup> d.w. as MeHg) than further out on the continental shelf (0.031 ± 0.71 ng Hg g<sup>-1</sup> d.w. as MeHg). We also observed a positive correlation between the MeHg:Hg ratio and previously characterized molecular markers of terrestrial organic matter (Bröder et al. Biogeosciences (2016) & Nature Com. (2018)). We thus suggest riverine inputs, rather than in situ MeHg formation, to explain observed MeHg trends.</p>


2004 ◽  
Vol 38 ◽  
pp. 106-114 ◽  
Author(s):  
Kunio Rikiishi ◽  
Junko Sakakibara

AbstractHistorical snow-depth observations in the former Soviet Union (FSU) during the period September 1960–August 1984 have been analyzed in order to understand the seasonal cycle of snow coverage in the FSU. Snow cover first appears in September in northeastern regions, and spreads over the entire territory before early January. Snowmelt begins in mid-January in the southern regions and then snow cover retreats rapidly northward until it disappears completely before late June. Northward of 60°N, the land surface is snow-covered for more than half the year. The longest snow-cover duration is observed on the central Siberian plateau (about 9.5 months) and along the Arctic coastal regions (about 8.5 months). One of the most conspicuous features of the snow coverage in the FSU is that the length of the snow-accumulation period differs considerably from region to region (2–7 months), while the length of the snowmelt period is rather short and uniform over almost the entire territory (1–2 months). Although the maximum snow depths are 20–50 cm in most regions of the FSU, they exceed 80 cm in the mountainous regions in central Siberia, Kamchatka peninsula, and along theYenisei river valley. Values for the maximum snow depth are very small along the Lena river valley in spite of the air temperature being extremely low in winter. By calculating correlation coefficients between the snowfall intensities and the sea-level pressures or 500 hPa heights, it is shown that deep snow along the Yenisei river valley is caused by frequent migration of synoptic disturbances from the Arctic Ocean. Snowfalls along the Lena river valley are also caused by traveling disturbances from the Arctic Ocean. Snow accumulation is suppressed after the Arctic Ocean has been frozen.


2021 ◽  
Vol 18 (17) ◽  
pp. 4919-4936
Author(s):  
Sergey N. Vorobyev ◽  
Jan Karlsson ◽  
Yuri Y. Kolesnichenko ◽  
Mikhail A. Korets ◽  
Oleg S. Pokrovsky

Abstract. Greenhouse gas (GHG) emission from inland waters of permafrost-affected regions is one of the key factors of circumpolar aquatic ecosystem response to climate warming and permafrost thaw. Riverine systems of central and eastern Siberia contribute a significant part of the water and carbon (C) export to the Arctic Ocean, yet their C exchange with the atmosphere remains poorly known due to lack of in situ GHG concentration and emission estimates. Here we present the results of continuous in situ pCO2 measurements over a 2600 km transect of the Lena River main stem and lower reaches of 20 major tributaries (together representing a watershed area of 1 661 000 km2, 66 % of the Lena's basin), conducted at the peak of the spring flood. The pCO2 in the Lena (range 400–1400 µatm) and tributaries (range 400–1600 µatm) remained generally stable (within ca. 20 %) over the night–day period and across the river channels. The pCO2 in tributaries increased northward with mean annual temperature decrease and permafrost increase; this change was positively correlated with C stock in soil, the proportion of deciduous needleleaf forest, and the riparian vegetation. Based on gas transfer coefficients obtained from rivers of the Siberian permafrost zone (k=4.46 m d−1), we calculated CO2 emission for the main stem and tributaries. Typical fluxes ranged from 1 to 2 gCm-2d-1 (>99 % CO2, <1 % CH4), which is comparable with CO2 emission measured in the Kolyma, Yukon, and Mackenzie rivers and permafrost-affected rivers in western Siberia. The areal C emissions from lotic waters of the Lena watershed were quantified by taking into account the total area of permanent and seasonal water of the Lena basin (28 000 km2 ). Assuming 6 months of the year to be an open water period with no emission under ice, the annual C emission from the whole Lena basin is estimated as 8.3±2.5 Tg C yr−1, which is comparable to the DOC and dissolved inorganic carbon (DIC) lateral export to the Arctic Ocean.


2021 ◽  
Author(s):  
Rene Preusker ◽  
Jan El Kassar ◽  
Bennet Juhls

&lt;p&gt;As air temperatures in the Arctic continue to rise, permafrost thaw intensifies, and discharge from the Arctic rivers increases. These drastic changes are likely to accelerate mobilization of organic matter and its export through rivers into the Arctic Ocean. Therefore, thorough monitoring of these processes becomes increasingly important. The Lena River with its large catchment area is one of the major sources of the organic carbon in the Arctic Ocean and, therefore, plays a crucial role in the Arctic carbon cycle.&amp;#160;&lt;br&gt;To observe current and future changes of carbon transport via the Lena River, a new monitoring program has been initiated in 2018. In situ water samples are collected from the one of the Lena Delta branches every several days. Since generally the in situ sampling in the Arctic is challenging and costly, in this study, we test the potential of remote sensing to complement the field observations. Remote sensing provides synoptic spatial coverages and high temporal resolution at high latitudes.&amp;#160;&lt;br&gt;We test the retrieval of dissolved organic carbon (DOC) from satellite-derived chromophoric dissolved organic matter (CDOM). For this, we use measurements of the Ocean &amp; Land Colour Instrument (OLCI) on board the Sentinel-3 satellites in combination with beforehand tested atmospheric correction algorithms and CDOM retrieval algorithms. The quality of the satellite retrieved DOC of the Lena River water is assessed by DOC, measured in the in situ samples. Remotely sensed DOC contributes to an improvement of DOC fluxes monitoring, which can potentially be extended to all big Arctic rivers.&lt;/p&gt;


2021 ◽  
Author(s):  
Olga Ogneva ◽  
Gesine Mollenhauer ◽  
Matthias Fuchs ◽  
Juri Palmtag ◽  
Tina Sanders ◽  
...  

&lt;p&gt;Rapid climate warming in the Arctic intensifies permafrost thaw, increases active layer depth in summer and enhances riverbank and coastal erosion. All of these cause additional release of organic matter (OM) into streams and rivers. OM will be (1) transformed and modified during transport and subsequently discharged into the Arctic Ocean, or (2) removed from the active cycling by sedimentation. Here, the nearshore zone (which includes deltas, estuaries and coasts) is of great importance, where the major transformation processes of terrestrial material take place. Despite the importance of deltas for the biogeochemical cycle, their functioning is poorly understood. For our study we examined the Lena River nearshore, which represents the world&amp;#8217;s third largest delta and supplies the second highest annual water and sediment discharge into the Arctic Ocean. Running through almost the entirety of East Siberia from Lake Baikal to the Laptev Sea, the Lena River drains an area of &amp;#8764;2,61&amp;#215;10&lt;sup&gt;6&lt;/sup&gt; km&lt;sup&gt;2&lt;/sup&gt;&amp;#160; with approximately 90% underlain by permafrost. Our aims were to investigate the spatial variation of OM concentration and isotopic composition during transit from terrestrial permafrost source to the ocean interface, and to compare riverine and deltaic OM composition. We measured particulate and dissolved organic carbon (POC and DOC) concentrations and their associated &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C and &amp;#8710;&lt;sup&gt;14&lt;/sup&gt;C values in water samples collected along a &amp;#8764;1500 km long Lena River transect from Yakutsk downstream to the river outlet into the Laptev Sea.&lt;/p&gt;&lt;p&gt;We find significant qualitative and quantitative differences between the OM composition in the Lena River main channel and its delta. Further, we found suspended matter and POC concentrations decreased during transit from river to the Arctic Ocean.&amp;#160; DOC concentrations in the Lena delta were almost 50% lower than OM from the main channel. We found that deltaic POC is depleted in &lt;sup&gt;13&lt;/sup&gt;C relative to fluvial POC, and that its &lt;sup&gt;14&lt;/sup&gt;C signature suggests a modern composition indicating phytoplankton origin. This observation likely reflects the difference in hydrological conditions between the delta and the river main channel, caused by lower flow velocity and average water depth. We propose that deltaic environments provide favorable growth conditions for riverine primary producers such as algae and aquatic plants. Deltaic DOC is depleted in &lt;sup&gt;14&lt;/sup&gt;C compared to riverine, especially in samples taken from the water surface, which indicates contributions from an additional old carbon stock source, specific for the Lena Delta. We suggest that this C is released from deltaic bank erosion and partly stays floating on the surface. In conclusion, we found a strong impact of deltaic processes on the fate and dominant signatures of OM discharged into the Arctic Ocean.&lt;/p&gt;


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