Pond Coverage Research Articles

Decadal trends in mangrove and pond aquaculture cover on Hainan (China) since 1966: mangrove loss, fragmentation and associated biogeochemical changes

Mangrove forests suffer from large-scale conversion into pond aquaculture worldwide. However, rarely can the detailed development of these changes and the consequences for coastal biogeochemistry be traced back to baseline conditions. We analyzed decadal changes in mangrove forest and aquaculture pond cover of five estuaries along the east coast of Hainan, northern South China Sea, using aerial photos and satellite images from 1966 to 2009. In addition, we reconstructed historical changes in the biogeochemistry by analyzing three sediment cores from the largest remaining mangrove area in east Hainan (Wenchang/Wenjiao Estuary, WWE). Overall mangrove loss was 72% (from 3697 ha in 1966 to 1041 ha in 2009), ranging from 63% in WWE to virtually 100% loss in Qingge. Land cover of aquaculture ponds in the five estuaries increased from 550 ha in 1966 to 3944 ha in 2009. 55% of the former mangrove area was directly replaced by aquaculture ponds accounting for 76% of the mangrove loss. An increase in the number of individual mangrove area patches from 230 larger to 2134 smaller patches indicates severe fragmentation of the remaining mangrove areas, likely with adverse consequences for ecosystem functioning. The sediment cores from the WWE show that the primary organic matter source changed from mangrove- to aquaculture-derived suspended matter since the 1980s. Moreover, the land cover change likely increased the nutrient export from land due to loss of the mangrove filter and creation of a significant nutrient source by pond effluents with negative impact for adjacent seagrass meadows and coral reefs. This is one of the longest time series documenting massive mangrove decline in recent decades. It highlights the strong and persistent ecological and biogeochemical changes associated with mangrove conversion in tropical estuaries, negatively affecting ecosystem services provided by undisturbed mangrove forests. The speed and magnitude of land conversion and the biogeochemical consequences for adjacent coastal waters observed in Hainan serve as an extreme example of similar activities in Southeast Asia.

Stormwater ponds: An overlooked but plentiful urban designer ecosystem provides invasive plant habitat in a subtropical region (Florida, USA)

Designed ecosystems are built as part of ongoing urban expansion, providing a suite of valued ecosystem services. However, these new ecosystems could also promote disservices by facilitating the colonization and spread of invasive species. We conduct the first assessment of the quantity and invasion of an overlooked designed ecosystem: stormwater ponds. These ponds are commonly recommended for managing urban hydrology, but little is known about their ecology or extent of proliferation. Using a broad-scale survey of pond coverage in Florida, USA, we found that over 76,000 stormwater ponds have been built just in this state, forming 2.7% of total urban land cover. This extensive pondscape of manufactured habitats could facilitate species spread throughout urban areas and into nearby natural waterbodies. We also conducted a survey of the severity of plant invasion in 30 ponds in Gainesville, FL, US across two pond types (dry vs. wet), and a gradient of management intensities (low, medium, high) and pond ages. We unexpectedly found a high number of invasive plant species (28 in just 30 ponds). Ninety-six percent of surveyed ponds contained from one to ten of these species, with ponds exhibiting high turnover in invader composition (i.e., high beta diversity). The bank sections of dry unmanaged ponds exhibited the highest mean invasive species richness (5.8 ± 1.3) and the inundated centers of wet medium managed ponds exhibited the highest mean invasive species cover (34 ± 12%). Invasive plant richness and cover also tended to be greater in dry ponds with higher soil nutrient levels, and in older wet ponds. Therefore, we found that highly maintained and younger wet ponds were the least invaded. Nevertheless, common management practices that limit plant invasions may also limit native species establishment and invasion may increase in the decades following pond construction.

Shallow Salt Marsh Tidal Ponds–An Environment With Extreme Oxygen Dynamics

In marshes, tidal ponds are increasing in number and areal coverage. Getting a better understanding of their unique biogeochemistry is a prerequisite for foreseeing their future role in salt marsh ecosystems. Using in situ microprofiling, this study investigated the spatiotemporal dynamics of O2, pH and CO2 in shallow salt marsh tidal ponds in the summer time. High benthic photosynthetic activity, fueled by CO2 from the sediment, resulted in steep vertical O2 gradients at the sediment-water interface, increasing from anoxia to extremely supersaturated peak concentrations up to 886±139 µmol L-1 (391% atmospheric O2 saturation) over a short distance of 6mm. These characteristic peaks developed even at low light conditions down to 150 µmol m-2 sec-1 photosynthetically active radiation (PAR). The oxygen gradients were restricted to the layer of benthic microalgae on the sediment surface and did not extend into the water column, which was well-mixed throughout the day showing no vertical variation. The benthic photosynthesis and respiration controlled the oxygen concentration in the water column, creating net supersaturated conditions during the day and hypoxic conditions at night. The tidal ponds were generally well-buffered showing only attenuated pH fluctuations ranging from 6.2 to 7.3, and no persistent gradients built up, despite the high photosynthetic activity at the sediment water interface. CO2 accumulated in the sediment and was present in the water column during the morning hours, but depleted in the afternoon due to the high photosynthetic uptake. Tidal ponds also experienced event-driven changes in their biogeochemistry. Sea foam developed on the water surface during the day and accumulated on one side of the pond blocking light penetration and lowering oxygen concentrations under the foam. Inundation at high tide caused a short-lived temporal variation in O2 and pH, which was restricted to the time of the flood. As the flooding water receded, the preceding O2 and pH conditions were immediately restored. Altogether shallow tidal ponds comprise a marsh habitat with distinctive spatiotemporal oxygen dynamics driven by benthic photosynthesis and respiration, which differ from the surrounding vegetated marsh, and could drive changes in salt marsh biogeochemistry in response to increased pond coverage.

Optimal Water Resources Regulation for the Pond Irrigation System Based on Simulation-A Case Study in Jiang-Huai Hilly Regions, China.

Due to the importance and complexity of water resources regulations in the pond irrigation systems of the Jiang-Huai hilly regions, a water allocation simulation model for pond irrigation districts based on system simulation theory was developed in this study. To maximize agricultural irrigation benefits while guaranteeing rural domestic water demand, an optimal water resources regulation model for pond irrigation districts and a simulation-based optimal water resources regulation technology system for the pond irrigation system were developed. Using this system, it was determined that the suitable pond coverage rate (pond capacity per unit area) was 2.92 × 105 m3/km2. Suitable water supply and operational rules for adjusting crop planting structure were also developed the water-saving irrigation method and irrigation system. To guarantee rural domestic water demand, the multi-year average total irrigation water deficit of the study area decreased by 4.66 × 104 m3/km2; the average multi-year water deficit ratio decreased from 20.40% to 1.18%; the average multi-year irrigation benefit increased by 1.11 × 105 RMB (16,128$)/km2; and the average multi-year revenue increased by 6.69%. Both the economic and social benefits were significant. The results of this study provide a theoretical basis and technological support for comprehensive pone governance in the Jiang-Huai hilly regions and promote the establishment of a water allocation scheme and irrigation system for pond irrigation districts, which have practical significance and important application value.

Decision support framework for solid waste management based on sustainability criteria: A case study of tailings pond cover systems

Abstract Tailings are one of the major categories of industrial waste, the disposal of which is problematic from an environmental viewpoint. The weathering of sulfide bearing waste materials commonly generates acidity and dissolved metals in the environment creating acid mine drainage (AMD). Typically, the chosen reclamation solutions emphasize low construction costs over environmental and technical sustainability challenging decision making. The aim of this work was to develop a framework for analysis of alternative cover scenarios with multiple-criteria decision analysis (MCDA) applied for the purpose. The case study comprised totally 10 criteria and five different cover structure options: moraine-based cover, biofuel fly ash/steel slag cover, stabilization with ordinary Portland cement or with composite binder, and use of an advanced hardpan cover liner (AHCL) system. The proposed methodological approach provides the structural steps of MCDA process to compare and contextually evaluate the economic, technical and social-ecological implications of cover alternatives. Modified Analytical Hierarchy Process (AHP) was applied as a MCDA approach for structuring complex problems and assisting decision makers to choose the best alternative among a discrete set of scenarios. Differing preferences of the stakeholders were resolved by synthetizing the conflicting weightings in the beginning of the analysis. Life-Cycle Assessment (LCA) was used to evaluate the social-ecological impacts of emissions, energy demand and impact to human health. Overall, the results from this study show that when considering total sustainability, the AHCL was preferred over the other alternatives when the weighting of the main technical, social-ecological and economic criteria was equal (33%). The weighting of main criteria and consequently sub-criteria impacts the ranking order of compared solutions. Decision making comprising viewpoints of different stakeholders is important when evaluating sustainability criteria. Higher weighting of social-ecological and technical criteria (50%) favored stabilization with composite binder while higher weighting (50%) of costs favored moraine cover. The proposed framework can process competing and conflicting objectives in addition to quantitative and qualitative criteria, hence providing a holistic and interdisciplinary approach to complex problems. The results from this project can help to develop sustainable remediation strategies to reduce the environmental risks associated with mine wastes.

Mangrove forests and aquaculture in the Mekong river delta

The mangrove area in Viet Nam is dramatically decreasing in the last decades. Since 1995, mangrove forests in south Viet Nam are allotted and contracted to households for protection, management and logging. Under this policy, households are allowed to convert 20–40% of the allotted forests into other uses, mainly shrimp farming. Most households develop mixed shrimp-mangrove farming systems, in which shrimp ponds are mixed with mangrove forest. With the poor enforcement of the forest assignment policy, however, the mangrove forest is over-extracted as farmers are converting more than the allowed level for larger water surface areas for shrimp farming and higher returns. In this study, we examine the impacts of mangrove coverage of mixed mangrove-shrimp ponds using the production and profit functions. Our analyses show that mangrove density has no impacts on shrimp farming. However, mangrove coverage affects productivity and profit of shrimp farming. The optimal mangrove coverage for shrimp farming is found to be approximately 60%. This implies that maintaining the level of mangrove coverage of 60% does not only to comply with the policy, but also bring about the highest level of output and profit for shrimp farmers.

A spectral mixture analysis approach to quantify Arctic first-year sea ice melt pond fraction using QuickBird and MODIS reflectance data

Melt ponds play a significant role in the summer decay of sea ice due to the fact that their albedo is significantly lower than surrounding snow and sea ice surface. Despite its requirement for thermodynamic sea ice modeling, measurement of melt pond areal coverage using satellite remote sensing has proven difficult due to significant spatiotemporal variability in the timing and evolution of melt ponds. Less than optimal results from prior studies employing a spectral mixture analysis (SMA) towards the determination of melt pond areal coverage from satellite remote sensing data provided the incentive for a multiple endmember spectral mixture analysis (MESMA) approach. The MESMA was performed on Moderate Resolution Imaging Spectroradiometer (MODIS) imagery using endmember spectra obtained from atmospherically corrected coincident high resolution imagery, surface observations and modeling. Results were validated against a high resolution Quickbird image acquired coincident to the MODIS image. The validation indicates that the best MESMA results provide consistent estimates of melt pond coverage for regions with high pond coverage (within 5% melt pond coverage) but overestimate pond fraction for regions with low pond coverage (by 10% or more). This may be due to deficiencies in the representation of sea ice surfaces within the endmember library used, oversimplified modeling of the ice surface and shortcomings in the validation process. However, it is assumed that with further refinement, the MESMA technique could allow for reliable estimates of the areal coverage of sea ice melt ponds using low resolution (large spatial coverage) optical satellite imagery under a wide variety of spatiotemporal pond evolution and fraction conditions.

A simple model for the evolution of melt pond coverage on permeable Arctic sea ice

Abstract. As the melt season progresses, sea ice in the Arctic often becomes permeable enough to allow for nearly complete drainage of meltwater that has collected on the ice surface. Melt ponds that remain after drainage are hydraulically connected to the ocean and correspond to regions of sea ice whose surface is below sea level. We present a simple model for the evolution of melt pond coverage on such permeable sea ice floes in which we allow for spatially varying ice melt rates and assume the whole floe is in hydrostatic balance. The model is represented by two simple ordinary differential equations, where the rate of change of pond coverage depends on the pond coverage. All the physical parameters of the system are summarized by four strengths that control the relative importance of the terms in the equations. The model both fits observations and allows us to understand the behavior of melt ponds in a way that is often not possible with more complex models. Examples of insights we can gain from the model are that (1) the pond growth rate is more sensitive to changes in bare sea ice albedo than changes in pond albedo, (2) ponds grow slower on smoother ice, and (3) ponds respond strongest to freeboard sinking on first-year ice and sidewall melting on multiyear ice. We also show that under a global warming scenario, pond coverage would increase, decreasing the overall ice albedo and leading to ice thinning that is likely comparable to thinning due to direct forcing. Since melt pond coverage is one of the key parameters controlling the albedo of sea ice, understanding the mechanisms that control the distribution of pond coverage will help improve large-scale model parameterizations and sea ice forecasts in a warming climate.

Nutrient availability limits biological production in Arctic sea ice melt ponds

Every spring and summer melt ponds form at the surface of polar sea ice and become habitats where biological production may take place. Previous studies report a large variability in the productivity, but the causes are unknown. We investigated if nutrients limit the productivity in these first-year ice melt ponds by adding nutrients to three enclosures ([1] PO43−, [2] NO3−, and [3] PO43− and NO3−) and one natural melt pond (PO43− and NO3−), while one enclosure and one natural melt pond acted as controls. After 7–13 days, Chl a concentrations and cumulative primary production were between two- and tenfold higher in the enclosures and natural melt ponds with nutrient addition compared with their respective controls, with the largest increase occurring in the enclosures. Separate additions of PO43− and NO3− in the enclosures led to intermediate increases in productivity, suggesting co-limitation of nutrients. Bacterial production and the biovolume of ciliates, which were the dominant grazers, were positively correlated with primary production, showing a tight coupling between primary production and both microbial activity and ciliate grazing. To our knowledge, this study is the first to ascertain nutrient limitation in melt ponds. We also document that the addition of nutrients, although at relative high concentrations, can stimulate biological productivity at several trophic levels. Given the projected increase in first-year ice, increased melt pond coverage during the Arctic spring and potential additional nutrient supply from, e.g. terrestrial sources imply that biological activity of melt ponds may become increasingly important for the sympagic carbon cycling in the future Arctic.

Aerial observations of sea ice and melt ponds near the North Pole during CHINARE2010

An aerial photography has been used to provide validation data on sea ice near the North Pole where most polar orbiting satellites cannot cover. This kind of data can also be used as a supplement for missing data and for reducing the uncertainty of data interpolation. The aerial photos are analyzed near the North Pole collected during the Chinese national arctic research expedition in the summer of 2010 (CHINARE2010). The result shows that the average fraction of open water increases from the ice camp at approximately 87°N to the North Pole, resulting in the decrease in the sea ice. The average sea ice concentration is only 62.0% for the two flights (16 and 19 August 2010). The average albedo (0.42) estimated from the area ratios among snow-covered ice, melt pond and water is slightly lower than the 0.49 of HOTRAX 2005. The data on 19 August 2010 shows that the albedo decreases from the ice camp at approximately 87°N to the North Pole, primarily due to the decrease in the fraction of snow-covered ice and the increase in fractions of melt-pond and open-water. The ice concentration from the aerial photos and AMSR-E (The Advanced Microwave Scanning Radiometer-Earth Observing System) images at 87.0°–87.5°N exhibits similar spatial patterns, although the AMSR-E concentration is approximately 18.0% (on average) higher than aerial photos. This can be attributed to the 6.25 km resolution of AMSR-E, which cannot separate melt ponds/submerged ice from ice and cannot detect the small leads between floes. Thus, the aerial photos would play an important role in providing high-resolution independent estimates of the ice concentration and the fraction of melt pond cover to validate and/or supplement space-borne remote sensing products near the North Pole.

Spatial, seasonal and interannual variability of supraglacial ponds in the Langtang Valley of Nepal, 1999–2013

ABSTRACTSupraglacial ponds play a key role in absorbing atmospheric energy and directing it to the ice of debris-covered glaciers, but the spatial and temporal distribution of these features is not well documented. We analyse 172 Landsat TM/ETM+ scenes for the period 1999–2013 to identify thawed supraglacial ponds for the debris-covered tongues of five glaciers in the Langtang Valley of Nepal. We apply an advanced atmospheric correction routine (Landcor/6S) and use band ratio and image morphological techniques to identify ponds and validate our results with 2.5 m Cartosat-1 observations. We then characterize the spatial, seasonal and interannual patterns of ponds. We find high variability in pond incidence between glaciers (May–October means of 0.08–1.69% of debris area), with ponds most frequent in zones of low surface gradient and velocity. The ponds show pronounced seasonality, appearing in the pre-monsoon as snow melts, peaking at the monsoon onset at 2% of debris-covered area, then declining in the post-monsoon as ponds drain or freeze. Ponds are highly recurrent and persistent, with 40.5% of pond locations occurring for multiple years. Rather than a trend in pond cover over the study period, we find high interannual variability for each glacier after controlling for seasonality.

Melt pond distribution and geometry in high Arctic sea ice derived from aerial investigations

ABSTRACTAerial photography was conducted in the high Arctic Ocean during a Chinese research expedition in summer 2010. By partitioning the images into three distinct surface categories (sea ice/snow, water and melt ponds), the areal fraction of each category, ice concentration and the size and geometry of individual melt ponds, are determined with high-spatial resolution. The ice concentration and melt pond coverage have large spatial deviations between flights and even between images from the marginal ice zone to the pack ice zone in the central Arctic. Ice concentration and pond coverage over high Arctic (from 84°N to north) was ~75% and ~6.8%, respectively, providing ‘ground truth’ for the unusual transpolar reduction strip of ice indicated concurrently by AMSR-E data and for the regions (north of 88°N) where no passive microwave sensors can cover. Melt pond size and shape distributions are examined in terms of pond area (S), perimeter (P), mean caliper dimension (MCD) (L), roundness (R), convex degree (C), the ratio of P/S and fractal dimension (D). Power-law relationships are developed between pond size and number. Some general trends in geometric metrics are identified as a function of pond area including R, C, P/S and D. The scale separation of pond complexity is demonstrated by analyzing area-perimeter data. The results will potentially help the modelling of melt pond evolution and the determination of heterogeneity of under-ice transmitted light fields.

A breeding site model for regional, dynamical malaria simulations evaluated using in situ temporary ponds observations.

Daily observations of potential mosquito developmental habitats in a suburb of Kumasi in central Ghana reveal a strong variability in their water persistence times, which ranged between 11 and 81 days. The persistence of the ponds was strongly tied with rainfall, location and size of the puddles. A simple power-law relationship is found to fit the relationship between the average pond depth and area well. A prognostic water balance model is derived that describes the temporal evolution of the pond area and depth, incorporating the power-law geometrical relation. Pond area increases in response to rainfall, while evaporation and infiltration act as sink terms. Based on a range of evaluation metrics, the prognostic model is judged to provide a good representation of the pond coverage evolution at most sites. Finally, we demonstrate that the prognostic equation can be generalised and equally applied to a grid-cell to derive a fractional pond coverage, and thus can be implemented in spatially distributed models for relevant vector- borne diseases such as malaria.

Albedo feedback enhanced by smoother Arctic sea ice

AbstractThe ICESat operational period 2003–2008 coincided with a dramatic decline in Arctic sea ice—linked to prolonged melt season duration and enhanced melt pond coverage. Although melt ponds evolve in stages, sea ice with smoother surface topography typically allows the pond water to spread over a wider area, reducing the ice‐albedo and accelerating further melt. Here we develop this theory into a quantitative relationship between premelt sea ice surface roughness and summer melt pond coverage. Our method, applied to ICESat observations of the end‐of‐winter sea ice roughness, can account for 85% of the variance in advanced very high resolution radiometer (AVHRR) observations of the summer ice‐albedo. An Arctic‐wide reduction in sea ice roughness from 2003 to 2008 explains a drop in ice‐albedo that resulted in a 16% increase in solar heat input to the sea ice cover, which represents ten times the heat input contributed by earlier melt onset timing over the same period.

Optical properties of melting first‐year Arctic sea ice

AbstractThe albedo and transmittance of melting, first‐year Arctic sea ice were measured during two cruises of the Impacts of Climate on the Eco‐Systems and Chemistry of the Arctic Pacific Environment (ICESCAPE) project during the summers of 2010 and 2011. Spectral measurements were made for both bare and ponded ice types at a total of 19 ice stations in the Chukchi and Beaufort Seas. These data, along with irradiance profiles taken within boreholes, laboratory measurements of the optical properties of core samples, ice physical property observations, and radiative transfer model simulations are employed to describe representative optical properties for melting first‐year Arctic sea ice. Ponded ice was found to transmit roughly 4.4 times more total energy into the ocean, relative to nearby bare ice. The ubiquitous surface‐scattering layer and drained layer present on bare, melting sea ice are responsible for its relatively high albedo and relatively low transmittance. Light transmittance through ponded ice depends on the physical thickness of the ice and the magnitude of the scattering coefficient in the ice interior. Bare ice reflects nearly three‐quarters of the incident sunlight, enhancing its resiliency to absorption by solar insolation. In contrast, ponded ice absorbs or transmits to the ocean more than three‐quarters of the incident sunlight. Characterization of the heat balance of a summertime ice cover is largely dictated by its pond coverage, and light transmittance through ponded ice shows strong contrast between first‐year and multiyear Arctic ice covers.

Influence of ice thickness and surface properties on light transmission through Arctic sea ice.

The observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role for amount and timing of sea‐ice‐melt and under‐ice primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of sea ice. We measured spectral under‐ice radiance and irradiance using the new Nereid Under‐Ice (NUI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. NUI is a next generation hybrid remotely operated vehicle (H‐ROV) designed for both remotely piloted and autonomous surveys underneath land‐fast and moving sea ice. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under‐ice optical measurements with three dimensional under‐ice topography (multibeam sonar) and aerial images of the surface conditions. We investigate the influence of spatially varying ice‐thickness and surface properties on the spatial variability of light transmittance during summer. Our results show that surface properties such as melt ponds dominate the spatial distribution of the under‐ice light field on small scales (<1000 m2), while sea ice‐thickness is the most important predictor for light transmission on larger scales. In addition, we propose the use of an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo.

Simulation of the melt season using a resolved sea ice model with snow cover and melt ponds

A three-dimensional sea ice model is presented with resolved snow thickness variations and melt ponds. The model calculates heating from solar radiative transfer and simulates the formation and movement of brine/melt water through the ice system. Initialization for the model is based on observations of snow topography made during the summer melt seasons of 2009, 2010, and 2012 from a location off the coast of Barrow, AK. Experiments are conducted to examine the importance of snow properties and snow and ice thickness by comparing observed and modeled pond fraction and albedo. One key process simulated by the model is the formation of frozen layers in the ice as relatively warm fresh water grid cells freeze when cooled by adjacent, cold brine-filled grid cells. These layers prevent vertical drainage and lead to flooding of melt water commonly observed at the beginning of the melt season. Flooding persists until enough heat is absorbed to melt through the frozen layer. The resulting long-term melt pond coverage is sensitive to both the spatial variability of snow cover and the minimum snow depth. For thin snow cover, initial melting results in earlier, reduced flooding with a small change in pond fraction after drainage of the melt water. Deeper snow tends to generate a delayed, larger peak pond fraction before drainage.

Physical and morphological properties of sea ice in the Chukchi and Beaufort Seas during the 2010 and 2011 NASA ICESCAPE missions

Physical and morphological properties of sea ice in the Chukchi and western Beaufort seas were measured during the 2010 and 2011 June−July ICESCAPE (Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment) missions aboard the USCGC Healy. Observations of ice conditions, including ice thicknesses, types, and concentrations of primary, secondary, and tertiary categories were reported at 2-h intervals while the ship was in transit using the Antarctic Sea ice Processes and Climate (ASPeCt) protocol. On-ice surveys of ice thickness, melt-pond depth, and ice properties (including profiles of internal temperature, salinity, and isotopic composition) were conducted at 21 total ice stations (12 in 2010 and 9 in 2011). Comparison to historical ship-based observations confirms a multi-decadal transition from a multiyear to thinner, first year -dominated seasonal sea-ice pack in the region, with much earlier ice retreat than in past decades. The ice encountered was predominantly (>98%) first year, with un-deformed ice thicknesses ranging from 0.73 to 1.2m. Pond coverage was extensive, averaging 29% in 2010 and 19% in 2011, resulting in considerable light absorption in the ice and transmission of light to the ocean. Enhanced melting near the ice edge is consistent with transport of Pacific-origin heat and/or ice-albedo feedbacks. Sediment entrainment was visible in 7.5% and 10.9% of the ice in 2010 and 2011, respectively. Overall, the results indicate a regime shift in the characteristics of the ice cover has occurred in the region over recent decades, with substantive implications for thermodynamic forcing, light availability in the upper ocean, and biological and biogeochemical processes in the ice and water column beneath. The results presented have applications for the interpretation of optical and biological measurements in the Chukchi Sea and serve as record of ice conditions for assessing long-term change.

The refreezing of melt ponds on Arctic sea ice

AbstractThe presence of melt ponds on the surface of Arctic sea ice significantly reduces its albedo, inducing a positive feedback leading to sea ice thinning. While the role of melt ponds in enhancing the summer melt of sea ice is well known, their impact on suppressing winter freezing of sea ice has, hitherto, received less attention. Melt ponds freeze by forming an ice lid at the upper surface, which insulates them from the atmosphere and traps pond water between the underlying sea ice and the ice lid. The pond water is a store of latent heat, which is released during refreezing. Until a pond freezes completely, there can be minimal ice growth at the base of the underlying sea ice. In this work, we present a model of the refreezing of a melt pond that includes the heat and salt balances in the ice lid, trapped pond, and underlying sea ice. The model uses a two‐stream radiation model to account for radiative scattering at phase boundaries. Simulations and related sensitivity studies suggest that trapped pond water may survive for over a month. We focus on the role that pond salinity has on delaying the refreezing process and retarding basal sea ice growth. We estimate that for a typical sea ice pond coverage in autumn, excluding the impact of trapped ponds in models overestimates ice growth by up to 265 million km3, an overestimate of 26%.

Management practices to enhance wildlife diversity of man-made fish ponds: the importance of the hydroperiod

We examined correlates of amphibian and waterbird diversity related to management practices, with a focus on timing of flooding, at shallow ponds used for common carp Cyprinus carpio culture in Eastern Poland. The age of the stocked fish was a strong predictor of amphibian diversity, with higher scores obtained in ponds with young-of-the-year carp compared to ponds containing older (and larger) fish. Pond cover by emergent vegetation was positively related to diversity of both taxonomic groups. The timing of filling affected the taxonomic richness of the ponds; in contrast to ponds filled in early spring (March-early April), early breeding amphibian species were not recorded in ponds filled later (early May). However, amphibian diversity did not differ between early- and late-flooded ponds. Early availability of filled ponds favored waterbird species richness and diversity, and the hydroperiod effect overcame the effect of fish age/size. Dissimilar responses to hydroperiod onset may reflect differences between amphibian and bird communities in the nature and strength of interactions with fish. Timing of flooding, which appears to be a neglected determinant of biodiversity in anthropogenic wetlands, should consider the breeding and migration phenology of wildlife species and the presence and population structure of fish.