Rapid physicochemical changes in the high Arctic Lake Kongressvatn caused by recent climate change

High Arctic lakes are among the most sensitive ecosystems and climate change strongly affects their physical properties, especially water temperature, and mixing processes. To study the effect of recent climate change on such a lake in the Arctic environment, we measured water chemistry and temperature from 2005 to 2010 in Kongressvatn, a crenogenic meromictic lake in Spitsbergen (Svalbard). In addition, we monitored water column temperatures during two consecutive years and compared them to regional air temperature data and physicochemical lake data from 1962 and 1968, two relatively cold years. Summer surface water temperature was highly correlated to air temperature, and both have increased by approximately 2°C since 1962. Temperature monitoring during 2?years showed that the warm summer of 2007 resulted in increased water temperatures even in the stratified, denser hypolimnion. Our water chemistry measurements showed that the chemocline position in 2005?C2010 was ca 12?m deeper than in 1962?C1968, and a second, weaker, chemocline appeared at metalimnetic depths of 7?C15?m. During the study period, the water level decreased by 4?m, and this change accelerated between 2008 and 2010. Our data support the hypothesis that water temperatures and stratification patterns are changing rapidly with air temperature, but changes in the catchment, such as glacial retreat and permafrost melting, may have an even stronger impact on lake properties.     

Interactions between climate change and contaminants

There is now general consensus that climate change is a global threat and a challenge for the 21st century. More and more information is available demonstrating how increased temperature may affect aquatic ecosystems and living resources or how increased water levels may impact coastal zones and their management. Many ecosystems are also affected by human releases of contaminants, for example from land based sources or the atmosphere, which also may cause severe effects. So far these two important stresses on ecosystems have mainly been discussed independently. The present paper is intended to increase awareness among scientists, coastal zone managers and decision makers that climate change will affect contaminant exposure and toxic effects and that both forms of stress will impact aquatic ecosystems and biota. Based on examples from different ecosystems, we discuss risks anticipated from contaminants in a rapidly changing environment and the research required to understand and predict how on-going and future climate change may alter risks from chemical pollution.     

The overlooked role of the ocean in mercury cycling in the Arctic

The rapid and high bioaccumulation of mercury in marine mammals and its spatial and temporal variations have been a major puzzle in the Arctic. While extensive efforts have been focussed on the monitoring and chemistry of atmospheric mercury depletion events, a recent mass budget estimate of mercury in the Arctic suggests that we have overlooked the role of the ocean itself. Only through focussed studies on Hg dynamics in the Arctic Ocean under a changing climate are we going to understand what the risk of mercury is to those marine ecosystems and the people who rely on them.     

New fjords,new coasts,new landscapes: The geomorphology of paraglacial coasts formed after recent glacier retreat in Brepollen (Hornsund,southern Svalbard)

Changes in the properties and dynamics of tidewater glacier systems are key indicators of the state of Arctic climate and environment. Calving of tidewater glacier fronts is currently the dominant form of ice mass loss and a major contributor to global sea-level rise. An important yet under-studied aspect of this process is transformation of Arctic landscapes, where new lands and coastal systems are revealed due to the recession of marine-terminating ice masses. The evolution of those freshly exposed paraglacial coastal environments is controlled by nearshore marine, coastal and terrestrial geomorphic processes, which rework glacial-derived sediments to create new coastal paraglacial landforms and landscapes. Here, we present the first study of the paraglacial coasts of Brepollen, one of the youngest bays of Svalbard revealed by ice retreat. We describe and classify coastal systems and the variety of landforms (deltas, cliffs, tidal flats, beaches) developed along the shores of Brepollen during the last 100 years. We further discuss the main modes of sediment supply to the coast in different parts of the new bay, highlighting the fast rate of coastal transformation as a paraglacial response to rapid deglaciation in the Arctic. This study provides an exemplar of likely coastal responses to be anticipated in similar tidewater settings under future climate change. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

Environment and biology of the Kara Sea: a general view for contamination studies

The recent revelation that over the past 30 years there has been a history of dumping waste including high-level radioactive wastes in the shallow Kara Sea has caused wide-spread concern. The potential impact of these contaminants and other non-nuclear pollutants in the Arctic ecosystem and on human health need to be assessed and, thus, a better insight gained on radioecological processes in cold waters. The present paper proposes a general view on the biology and the environment of the Kara Sea, as a basic tool for the experimental and modelling assessments of the impact of these contaminants.     

On the winter evolution of snow thermophysical properties over land‐fast first‐year sea ice

The geophysical, thermodynamic and dielectric properties of snow are important state variables that are known to be sensitive to Arctic climate variability and change. Given recent observations of changes in the Arctic physical system (Arctic Climate Impact Assessment, 2004), it is important to focus on the processes that give rise to variability in the horizontal, vertical and temporal dimensions of the life‐history of snow on sea ice. The objectives in this study are to present these ‘state’ variables and to investigate the processes that govern variability in the vertical, horizontal and temporal dimension by using a case study over land‐fast first‐year sea ice for the period December 2003 to June 2004. Results from two sampling areas (thin and thick snowpacks) show that differences in snowpack thickness can substantially change the vertical and temporal evolution of snow properties. During the late fall and early winter (cooling period) we measured no significant changes in the physical properties, except for thin snow‐cover salinity, which decreased throughout the period. Fall‐snow desalination was only observed under thin snowpacks with a rate of ?0·12 ppt day^?1. Significant changes occurred in the late winter and early spring (warming period), especially for snow grain size. Snow grain kinetic growth of 0·25–0·48 mm·day^?1 was measured coincidently with increasing salinity and wetness for both thin and thick snowpacks. Copyright © 2006 John Wiley & Sons, Ltd.     

Assessment aspect of contamination of the Arctic estuary ecosystems

Estuarine ecosystem may be considered as ‘pulse-targets’ where information about contamination of all-river basin and about scale and forms of contaminants input to the seas is concentrated. The nucleus of the estuarine processes of contaminants transformation and sedimentation is the critical salinity zone. In the real natural conditions of the Arctic the salinity dependent processes are masked by hydrodynamic effect. The tasks of effective chemical and biological monitoring of Russian Arctic estuarine ecosystems are formulated.     

Arctic Mackenzie Delta channel planform evolution during 1983–2013 utilising Landsat data and hydrological time series

Arctic deltas, such as the Mackenzie Delta, are expected to face major climate change and increased human influence in the near future. Deltas are characterised by highly dynamic fluvial processes, and changing climate will cause considerable evolution of the riverine environment. The changes are difficult to predict with existing knowledge and data. This study quantified channel planform change of the Mackenzie Delta (1983–2013), analysing its temporal and spatial patterns. We addressed the main obstacle of research on large remote areas, the lack of data, by developing a unique work flow that utilised Landsat satellite imagery, hydrological time series, remote sensing‐based change analysis, and automatic vectorisation of channels. Our results indicate that the Mackenzie Delta experienced constant evolution but at a highly varying rate over the 30 years. The study demonstrates that the magnitude and duration of flood peaks and the presence of spring ice breakup floods determine the rate of Arctic delta planform change. Changing winter conditions and spring flood magnitudes may therefore affect the stability of Arctic deltas. However, no clear trends towards decreased recurrence or magnitude of spring floods or increased instability of the delta plain have yet been observed in the Mackenzie Delta. The delta plain was most dynamic at the beginning and at the end of the examined period, corresponding to intense flooding, whereas the rates of change were subtle during the low‐flood period 1994–2007. The largest changes have occurred along the wide Middle Channel and in the outermost delta. Relative to their size, however, smaller meandering channels have been highly dynamic. Hotspots of change in the delta plain are located in anastomosing and braiding channel segments and, at the local scale, in point bars and cut‐banks along meandering channels. Our study describes how Landsat satellite data can be utilised for advancing fluvial geomorphological research in remote areas. However, cloudiness in the delta restricts production of dense time series with simultaneous coverage of the whole area and requires manual preprocessing.     

气候变化对湖库水环境的潜在影响研究进展

本文着重归纳气候变化对湖库热力特性、冰期、溶解氧、营养盐、浮游植物和水生植物等方面的影响规律,探讨气候变化对湖库水环境潜在影响的区域差异,讨论现有研究方法的优缺点和发展前景.研究表明,气候变暖对湖库物理过程的影响最为显著;热带草原气候和温带海洋性气候对于气候变暖和降雨变化的响应较其他气候类型突出;气候变化对湖库水环境的影响效果具有两面性.通过分析各气候类型中气候变暖对磷水平的潜在影响差异表明,亚热带季风气候的湖库更可能受气候变暖的影响趋于富营养状态.在今后研究中,建议深入开展各气候类型中区域性气候变化对湖库水环境影响的实例研究.     

Water source dynamics of high Arctic river basins

Arctic river basins are amongst the most vulnerable to climate change. However, there is currently limited knowledge of the hydrological processes that govern flow dynamics in Arctic river basins. We address this research gap using natural hydrochemical and isotopic tracers to identify water sources that contributed to runoff in river basins spanning a gradient of glacierization (0–61%) in Svalbard during summer 2010 and 2011. Spatially distinct hydrological processes operating over diurnal, weekly and seasonal timescales were characterized by river hydrochemistry and isotopic composition. Two conceptual water sources (‘meltwater’ and ‘groundwater’) were identified and used as a basis for end‐member mixing analyses to assess seasonal and year‐to‐year variability in water source dynamics. In glacier‐fed rivers, meltwater dominated flows at all sites (typically >80%) with the highest contributions observed at the beginning of each study period in early July when snow cover was most extensive. Rivers in non‐glacierized basins were sourced initially from snowmelt but became increasingly dependent on groundwater inputs (up to 100% of total flow volume) by late summer. These hydrological changes were attributed to the depletion of snowpacks and enhanced soil water storage capacity as the active layer expanded throughout each melt season. These findings provide insight into the processes that underpin water source dynamics in Arctic river systems and potential future changes in Arctic hydrology that might be expected under a changing climate. Copyright © 2013 John Wiley & Sons, Ltd.     

Toward Improved Estimation of the Dynamic Topography and Ocean Circulation in the High Latitude and Arctic Ocean: The Importance of GOCE

The Arctic plays a fundamental role in the climate system and shows significant sensitivity to anthropogenic climate forcing and the ongoing climate change. Accelerated changes in the Arctic are already observed, including elevated air and ocean temperatures, declines of the summer sea ice extent and sea ice thickness influencing the albedo and CO₂ exchange, melting of the Greenland Ice Sheet and increased thawing of surrounding permafrost regions. In turn, the hydrological cycle in the high latitude and Arctic is expected to undergo changes although to date it is challenging to accurately quantify this. Moreover, changes in the temperature and salinity of surface waters in the Arctic Ocean and Nordic Seas may also influence the flow of dense water through the Denmark Strait, which are found to be a precursor for changes in the Atlantic meridional overturning circulation with a lead time of around 10 years (Hawkins and Sutton in Geophys Res Lett 35:L11603, 2008). Evidently changes in the Arctic and surrounding seas have far reaching influences on regional and global environment and climate variability, thus emphasizing the need for advanced quantitative understanding of the ocean circulation and transport variability in the high latitude and Arctic Ocean. In this respect, this study combines in situ hydrographical data, surface drifter data and direct current meter measurements, with coupled sea ice–ocean models, radar altimeter data and the latest GOCE-based geoid in order to estimate and assess the quality, usefulness and validity of the new GOCE-derived mean dynamic topography for studies of the ocean circulation and transport estimates in the Nordic Seas and Arctic Ocean.     

Diagnostic monitoring of a changing environment: an alternative UK perspective

Adaptive management of the marine environment requires an understanding of the complex interactions within it. Establishing levels of natural variability within and between marine ecosystems is a necessary prerequisite to this process and requires a monitoring programme which takes account of the issues of time, space and scale. In this paper, we argue that an ecosystem approach to managing the marine environment should take direct account of climate change indicators at a regional level if it is to cope with the unprecedented change expected as a result of human impacts on the earth climate system. We discuss the purpose of environmental monitoring and the importance of maintaining long-term time series. Recommendations are made on the use of these data in conjunction with modern extrapolation and integration tools (e.g. ecosystem models, remote sensing) to provide a diagnostic approach to the management of marine ecosystems, based on adaptive indicators and dynamic baselines.     

The Barents Sea impact study (BASIS): methodology and first results

Global and climate changes are subject to scientific, societal and political debates. Recent observational evidence and results of global climate models have identified the circumpolar North as a region particularly susceptible to future climate change. To understand and assess the consequences of these changes for environmental and societal components of the European Arctic, the Barents Sea Impact Study (BASIS), an EU-funded integrated regional impact study (IRIS) has been carried out (ENV4-CT-97-0637). In common with global integrated assessments (IAs), IRISs also take a holistic view on climate change and its impact. Contrary to IAs, however, IRISs adopt a regional to sub-regional spatial scale. BASIS was carried out by an interdisciplinary team of specialists from 13 institutions in 6 countries. Major results pertain to impacts of possible climate change on marine and terrestrial ecosystems, freshwater hydrology, marine trace gas budgets, forestry and fishery. However, in this paper we focus on the major methodological aspects of an IRIS in general and on methods applied in BASIS in particular.     

Variations in submarine groundwater runoff as a possible cause of decomposition of marine methane-hydrates in the Artcic

The formation conditions and the dynamics of groundwater in the upper hydrodynamic zone of the northern coast of European Russia, which discharge directly into the Barents and White seas, are analyzed. The normal annual water, ionic, and thermal runoff and the anticipated submarine groundwater runoff into the Arctic Ocean are evaluated. The stability of marine arctic methane-hydrates under the observed and anticipated climate changes is analyzed. A physical substantiation is given to the concept of climate-determined increase in submarine groundwater discharge as a possible cause of the intensification of arctic methane hydrate decomposition, which does not contradict empirical data.     

A coupled tide-wave model for the NW European shelf seas

Understanding the interaction of tides and waves is essential in many studies, including marine renewable energy, sediment transport, long-term seabed morphodynamics, storm surges and the impacts of climate change. In the present research, a COAWST model of the NW European shelf seas has been developed and applied to a number of physical processes. Although many aspects of wave–current interaction can be investigated by this model, our focus is on the interaction of barotropic tides and waves at shelf scale. While the COWAST model was about five times more computationally expensive than running decoupled ROMS (ocean model) and SWAN (wave model), it provided an integrated modelling system which could incorporate many wave–tide interaction processes, and produce the tide and wave parameters in a unified file system with a convenient post-processing capacity. Some applications of the model such as the effect of tides on quantifying the wave energy resource, which exceeded 10% in parts of the region, and the effect of waves on the calculation of the bottom stress, which was dominant in parts of the North Sea and Scotland, during an energetic wave period are presented, and some challenges are discussed. It was also shown that the model performance in the prediction of the wave parameters can improve by 25% in some places where the wave-tide interaction is significant.     

Engineering and hydrogeological problems associated with in situ treatment

Abstract

Most organic materials that contaminate soil and the subsurface environment are readily degraded by natural biological processes. To this degree, in situ bioremediation can be thought of as a highly successful purification process. However, some organic molecules are naturally refractory to biodegradation, or other environmental factors induce molecular recalcitrance such as the absence of a proper microbial population or the presence of unsuitable environmental conditions. Examples of recalcitrant groundwater contaminants are soluble components of petroleum hydrocarbons (BTEX) and chlorinated aliphatic hydrocarbons (CAHs). Organic recalcitrance may be changed through introduction of degrading populations of microorganisms or by changing the environmental conditions through introduction of nutrients or other chemicals. The most significant engineering deficiency in in situ bioremediation is the absence of proven methods to introduce such materials into the subsurface environment for efficient mixing with microorganisms and the contaminants of concern.     

Surveillance for previously unmonitored organic contaminants in the San Francisco Estuary

The San Francisco Estuary Regional Monitoring Program initiated surveillance monitoring to identify previously unmonitored synthetic organic contaminants in the San Francisco Estuary. Organic extracts of water samples were analyzed using gas chromatography-mass spectrometry in full scan mode. The major contaminant classes identified in the samples were fire retardants, pesticides, personal care product ingredients, and plasticizers. Evidence from the literature suggests that some of these contaminants can persist in the environment, induce toxicity, and accumulate in marine biota and in higher food chain consumers. The major sources of these contaminants into the marine environment are the discharge of municipal and industrial wastewater effluents, urban stormwater, and agricultural runoff. As a proactive effort, it is suggested that surveillance studies be used routinely in monitoring programs to identify and prevent potential problem contaminants from harming the marine environment.     

海底天然气渗漏的地球物理特征及识别方法

海底天然气渗漏是在海洋环境中广泛分布的自然现象.海底天然气渗漏可以指示沉积层中的烃类聚集带,渗漏出的大量气体（主要是甲烷）可能影响全球的气候变化,此外,与海底渗漏相关的浅层气改变了海底沉积物的土工性质,可能对海底工程构成威胁.因此海底渗漏研究意义重大.海底天然气渗漏不仅影响海底沉积物的物理性质,而且还极大地改变海底地形地貌,它能在海底形成麻坑、泥火山、冷泉碳酸盐岩以及化学自养生物群落等现象.在海底渗漏发生的地方,地形地貌特征可以在海洋测深和逆向散射数据上得到反映;沉积物的声学特征可以在地震剖面上得到反映,如形成声混浊、声空白、亮点、多次波、速度下拉等;有些渗漏在海面形成油渍膜,油渍膜可以在合成孔径雷达图像上得到反映.根据海底渗漏的上述地球物理特征,可以识别出可能渗漏区域,海底渗漏的证实需要用到海底观测和取样分析资料.     

Impact of oceans on climate change in drylands

Drylands account for approximately 41% of the global total land area. Significant warming and rare precipitation in drylands result in a fragile ecology and deterioration of the living environment, making it more sensitive to global climate change. As an important regulator of the Earth's climate system, the oceans play a vital role in the process of climate change in drylands. In modern climate change in particular, the impact of marine activities on climate change in drylands cannot be neglected. This paper reviews the characteristics of climate change in drylands over the past 100 years, and summarizes the researches conducted on the impact of marine activities on these changes. The review focuses on the impact of the Pacific Decadal Oscillation(PDO), Atlantic Multidecadal Oscillation(AMO), El Ni?o and La Ni?a on climate change in drylands, and introduces the mechanisms by which different oceanic oscillation factors synergistically affect climate change in drylands.Studies have shown that global drylands have experienced a significant intensification in warming in the past 100 years, which shows obvious characteristics of interdecadal dry/wet variations. The characteristics of these changes are closely related to the oscillatory factors of the oceanic interdecadal scale. Different phase combinations of oceanic oscillation factors significantly change the land-sea thermal contrast, which in turn affects the westerly jet, planetary wave and blocking frequency, resulting in changes in the temperature and dry/wet characteristics of drylands. With the intensification of climate change in drylands, the impact of marine activities on these regions will reveal new characteristics in the future, which will increase the uncertainty of future climate change in drylands and intensify the impact of these drylands on global climate.     

New satellite derived sea ice motion tracks Arctic contamination

Sea ice has been reported to contain contaminants from atmospheric and nearshore sediment resuspension processes. In this study successive passive microwave images from the 85.5 GHz channels on the Special Sensor Microwave Imager (SSM/I) were merged with drifting buoy trajectories from the International Arctic Buoy Program to compute Arctic sea ice motion in the Russian Arctic between 1988 and 1994. Smooth daily motion fields were averaged to prepare monthly maps making it possible to compute the 7-year mean and mean seasonal ice motions as well as principal components of directional variability of sea ice motion for the entire Arctic and surrounding basins. These mean motion vectors are used to simulate the advection of contaminants deposited on or contained within the sea ice and subsequently transported into the Arctic Ocean in order to predict both their mean trajectories and dispersal over time. The 3-year displacement of contaminants from a number of Russian sites and one American site display various behaviours from substantial displacement and dispersal to almost no movement. This computational procedure could be applied to realtime SSM/I and ice buoy data to provide detailed, all-weather, vector motion maps of ice circulation to predict the path and dispersal of any new substance introduced to the sea ice and transported into the Arctic or Antarctic ocean surface.