The role of snow/ice cover in the formation of a local Himalayan circulation

2013 ◽  
Vol 120 (1-2) ◽  
pp. 45-51 ◽  
Author(s):  
Shupo Ma ◽  
Libo Zhou ◽  
Han Zou ◽  
Meigen Zhang ◽  
Peng Li
Keyword(s):  
Ice Cover

scholarly journals Sustaining observations in the polar oceans

2014 ◽  
Vol 372 (2025) ◽  
pp. 20130337 ◽  
Author(s):  
E. P. Abrahamsen
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
Ice Cover ◽  
Global Ocean ◽  
Shelf Seas ◽  
Polar Oceans ◽  
Global Ocean Circulation ◽  
Coordination And Collaboration ◽  
Temperature Depth

Polar oceans present a unique set of challenges to sustained observations. Sea ice cover restricts navigation for ships and autonomous measurement platforms alike, and icebergs present a hazard to instruments deployed in the upper ocean and in shelf seas. However, the important role of the poles in the global ocean circulation provides ample justification for sustained observations in these regions, both to monitor the rapid changes taking place, and to better understand climate processes in these traditionally poorly sampled areas. In the past, the vast majority of polar measurements took place in the summer. In recent years, novel techniques such as miniature CTD (conductivity–temperature–depth) tags carried by seals have provided an explosion in year-round measurements in areas largely inaccessible to ships, and, as ice avoidance is added to autonomous profiling floats and gliders, these promise to provide further enhancements to observing systems. In addition, remote sensing provides vital information about changes taking place in sea ice cover at both poles. To make these observations sustainable into the future, improved international coordination and collaboration is necessary to gain optimum utilization of observing networks.

scholarly journals Future projections of temperature and mixing regime of European temperate lakes

2019 ◽  
Vol 23 (3) ◽  
pp. 1533-1551 ◽  
Author(s):  
Tom Shatwell ◽  
Wim Thiery ◽  
Georgiy Kirillin
Keyword(s):  
Climate Warming ◽  
Mixed Layer Depth ◽  
Ice Cover ◽  
Climate Projections ◽  
Lake Model ◽  
Lake Morphology ◽  
Mixing Regime ◽  
Physical Response ◽  
Lake Characteristics

Abstract. The physical response of lakes to climate warming is regionally variable and highly dependent on individual lake characteristics, making generalizations about their development difficult. To qualify the role of individual lake characteristics in their response to regionally homogeneous warming, we simulated temperature, ice cover, and mixing in four intensively studied German lakes of varying morphology and mixing regime with a one-dimensional lake model. We forced the model with an ensemble of 12 climate projections (RCP4.5) up to 2100. The lakes were projected to warm at 0.10–0.11 ∘C decade−1, which is 75 %–90 % of the projected air temperature trend. In simulations, surface temperatures increased strongly in winter and spring, but little or not at all in summer and autumn. Mean bottom temperatures were projected to increase in all lakes, with steeper trends in winter and in shallower lakes. Modelled ice thaw and summer stratification advanced by 1.5–2.2 and 1.4–1.8 days decade−1 respectively, whereas autumn turnover and winter freeze timing was less sensitive. The projected summer mixed-layer depth was unaffected by warming but sensitive to changes in water transparency. By mid-century, the frequency of ice and stratification-free winters was projected to increase by about 20 %, making ice cover rare and shifting the two deeper dimictic lakes to a predominantly monomictic regime. The polymictic lake was unlikely to become dimictic by the end of the century. A sensitivity analysis predicted that decreasing transparency would dampen the effect of warming on mean temperature but amplify its effect on stratification. However, this interaction was only predicted to occur in clear lakes, and not in the study lakes at their historical transparency. Not only lake morphology, but also mixing regime determines how heat is stored and ultimately how lakes respond to climate warming. Seasonal differences in climate warming rates are thus important and require more attention.

scholarly journals Conditions of spatiotemporal variability of the thickness of the ice cover on lakes in the Tatra Mountains

2020 ◽  
Vol 17 (10) ◽  
pp. 2369-2386
Author(s):  
Maksymilian Solarski ◽  
Mirosław Szumny
Keyword(s):  
Snow Cover ◽  
Winter Season ◽  
Ice Cover ◽  
Spatiotemporal Variability ◽  
Ice Thickness ◽  
Tatra Mountains ◽  
Cover Thickness ◽  
The Tatra Mountains ◽  
The Impact

Abstract This research aimed to identify the impact of local climatic and topographic conditions on the formation and development of the ice cover in high-mountain lakes and the representativeness assessment of periodic point measurements of the ice cover thickness by taking into consideration the role of the avalanches on the icing of the lakes. Field works included measurement of the ice and snow cover thickness of seven lakes situated in the Tatra Mountains (UNESCO biosphere reserve) at the beginning and the end of the 2017/2018 winter season. In addition, morphometric, topographic and daily meteorological data of lakes from local IMGW (Polish Institute of Meteorology and Water Management) stations and satellite images were used. The obtained results enabled us to quantify the impact of the winter eolian snow accumulation on the variation in ice thickness. This variation was ranging from several centimetres up to about 2 meters and had a tendency to increase during the winter season. The thickest ice covers occurred in the most shaded places in the direct vicinity of rock walls. The obtained results confirm a dominating role of the snow cover in the variation of the ice thickness within individual lakes.

scholarly journals Warm Greenland during the last interglacial: the role of regional changes in sea ice cover

2016 ◽  
Vol 12 (10) ◽  
pp. 2011-2031 ◽  
Author(s):  
Niklaus Merz ◽  
Andreas Born ◽  
Christoph C. Raible ◽  
Thomas F. Stocker
Keyword(s):  
Sea Ice ◽  
Ice Cover ◽  
Labrador Sea ◽  
Last Interglacial ◽  
Atlantic Sector ◽  
Nordic Seas ◽  
Proxy Records ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract. The last interglacial, also known as the Eemian, is characterized by warmer than present conditions at high latitudes. This is implied by various Eemian proxy records as well as by climate model simulations, though the models mostly underestimate the warming with respect to proxies. Simulations of Eemian surface air temperatures (SAT) in the Northern Hemisphere extratropics further show large variations between different climate models, and it has been hypothesized that this model spread relates to diverse representations of the Eemian sea ice cover. Here we use versions 3 and 4 of the Community Climate System Model (CCSM3 and CCSM4) to highlight the crucial role of sea ice and sea surface temperatures changes for the Eemian climate, in particular in the North Atlantic sector and in Greenland. A substantial reduction in sea ice cover results in an amplified atmospheric warming and thus a better agreement with Eemian proxy records. Sensitivity experiments with idealized lower boundary conditions reveal that warming over Greenland is mostly due to a sea ice retreat in the Nordic Seas. In contrast, sea ice changes in the Labrador Sea have a limited local impact. Changes in sea ice cover in either region are transferred to the overlying atmosphere through anomalous surface energy fluxes. The large-scale spread of the warming resulting from a Nordic Seas sea ice retreat is mostly explained by anomalous heat advection rather than by radiation or condensation processes. In addition, the sea ice perturbations lead to changes in the hydrological cycle. Our results consequently imply that both temperature and snow accumulation records from Greenland ice cores are sensitive to sea ice changes in the Nordic Seas but insensitive to sea ice changes in the Labrador Sea. Moreover, the simulations suggest that the uncertainty in the Eemian sea ice cover accounts for 1.6 °C of the Eemian warming at the NEEM ice core site. The estimated Eemian warming of 5 °C above present day based on the NEEM δ15N record can be reconstructed by the CCSM4 model for the scenario of a substantial sea ice retreat in the Nordic Seas combined with a reduced Greenland ice sheet.

The Role of Ice Cover in the Formation of Bottom Sediment Chemical Composition on the East Siberian Shelf

2021 ◽  
Vol 59 (6) ◽  
pp. 585-598
Author(s):  
A. S. Astakhov ◽  
I.A. Kalugin ◽  
Xuefa Shi ◽  
K. I. Aksentov ◽  
A. V. Darin ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Bottom Sediment ◽  
Ice Cover ◽  
East Siberian Shelf ◽  
Siberian Shelf

The effect of irradiance and temperature on the role of photolysis in the removal of organic micropollutants under Antarctic conditions

2013 ◽  
Vol 10 (5) ◽  
pp. 417 ◽  
Author(s):  
Philipp Emnet ◽  
Rai S. Kookana ◽  
Ali Shareef ◽  
Sally Gaw ◽  
Mike Williams ◽  
...  
Keyword(s):  
Environmental Fate ◽  
Limit Of Detection ◽  
Ice Cover ◽  
Degradation Pathway ◽  
Organic Micropollutants ◽  
Abstract Knowledge ◽  
Photolytic Degradation ◽  
Untreated Sewage ◽  
The Antarctic

Environmental context Antarctica has several scientific research stations located along its coast, where they discharge often untreated sewage containing organic micropollutants. Although degradation of these pollutants by microorganisms is limited by the cold conditions, other pathways such as photodegradation may be significant. Our results indicate that, during the summer, photolysis is a potentially significant degradation pathway for organic micropollutants in Antarctic surface waters, although the rate of loss would depend on ice cover and water depth. Abstract Knowledge of the environmental fate of organic micropollutants in Antarctica is limited, especially with respect to photolysis. The Antarctic is characterised by extreme light conditions of either continuous sunshine or darkness depending on the season. The photolytic degradation of benzophenone-3 (BP-3), bisphenol A (BPA), 17α-ethinylestradiol (EE2), methyl paraben (mParaben), 4-t-octylphenol (4-t-OP) and triclosan in MilliQ and seawater was investigated over a range of irradiance levels and temperatures. Photodegradation was compound specific. Up to 20% of BPA, BP-3 and EE2 was degraded over a 7-h irradiance period. Triclosan and 4-t-OP degraded to below the limit of detection in all experiments whereas mParaben was not degraded. The degradation of triclosan increased with irradiance in both MilliQ (P=2.2×10–16) and seawater (P=2.2×10–16). The degradation of 4-t-OP increased with irradiance in MilliQ (P=8.5×10–9) and seawater (P=1.1×10–5), and with temperature in MilliQ (P=8.5×10–9) and seawater (P=1.0×10–5). Similar relationships could not be established for BPA, BP-3, EE2 and mParaben due to the limited extent of degradation observed. The photolysis of triclosan was enhanced 4-fold in seawater compared to MilliQ water. Results from this study indicate that micropollutants may persist for extended periods of time in Antarctic coastal waters, particularly with ice cover, above and beyond that exhibited in temperate seawater.

The response and role of ice cover in lake-climate interactions

2010 ◽  
Vol 34 (5) ◽  
pp. 671-704 ◽  
Author(s):  
Laura C. Brown ◽  
Claude R. Duguay
Keyword(s):  
Climate Models ◽  
Weather Forecasting ◽  
Regional Climate ◽  
Remote Sensing Data ◽  
Ice Cover ◽  
Climate Modelling ◽  
Lake Ice ◽  
Climate Conditions ◽  
Global Circulation Models

This paper reviews the current state of knowledge pertaining to the interactions of lake ice and climate. Lake ice has been shown to be sensitive to climate variability through observations and modelling, and both long-term and short-term trends have been identified from ice records. Ice phenology trends have typically been associated with variations in air temperatures while ice thickness trends tend to be associated more to changes in snow cover. The role of ice cover in the regional climate is less documented and with longer ice-free seasons possible as a result of changing climate conditions, especially at higher latitudes, the effects of lakes on their surrounding climate (such as increased evaporation, lake-effect snow and thermal moderation of surrounding areas, for example) can be expected to become more prominent. The inclusion of lakes and lake ice in climate modelling is an area of increased attention in recent studies. An important step in improving predictions of ice conditions in models is the assimilation of remote sensing data in areas where in-situ data is lacking, or non-representative of the lake conditions. The ability to accurately represent ice cover on lakes will be an important step in the improvement of global circulation models, regional climate models and numerical weather forecasting.

scholarly journals The Role of Northern Sea Ice Cover for the Weakening of the Thermohaline Circulation under Global Warming

2007 ◽  
Vol 20 (16) ◽  
pp. 4160-4171 ◽  
Author(s):  
A. Levermann ◽  
J. Mignot ◽  
S. Nawrath ◽  
S. Rahmstorf
Keyword(s):  
Global Warming ◽  
Sea Ice ◽  
Heat Loss ◽  
Climate Models ◽  
Thermohaline Circulation ◽  
Ice Cover ◽  
Near Surface ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract An increase in atmospheric CO2 concentration and the resulting global warming are typically associated with a weakening of the thermohaline circulation (THC) in model scenarios. For the models participating in the Coupled Model Intercomparison Project (CMIP), this weakening shows a significant (r = 0.62) dependence on the initial THC strength; it is stronger for initially strong overturning. The authors propose a physical mechanism for this phenomenon based on an analysis of additional simulations with the coupled climate models CLIMBER-2 and CLIMBER-3α. The mechanism is based on the fact that sea ice cover greatly reduces heat loss from the ocean. The extent of sea ice is strongly influenced by the near-surface atmospheric temperature (SAT) in the North Atlantic but also by the strength of the THC itself, which transports heat to the convection sites. Consequently, sea ice tends to extend farther south for weaker THC. Initially larger sea ice cover responds more strongly to atmospheric warming; thus, sea ice retreats more strongly for an initially weaker THC. This sea ice retreat tends to strengthen (i.e., stabilize) the THC because the sea ice retreat allows more oceanic heat loss. This stabilizing effect is stronger for runs with weak initial THC and extensive sea ice cover. Therefore, an initially weak THC weakens less under global warming. In contrast to preindustrial climate, sea ice melting presently plays the role of an external forcing with respect to THC stability.

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