1928 research outputs found
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Challenges of deep-sea biodiversity assessments in the Southern Ocean
Get PDFDespite recent progress in deep-sea biodiversity assessments in the Southern Ocean (SO), there remain gaps in our knowledge that hamper efficient deep-sea monitoring in times of rapid climate change. These include geographical sampling bias, depth and size-dependent faunal gaps in biology, ecology, distribution, and phylogeography, and the evolution of SO species. The phenomena of species patchiness and rarity are still not well understood, possibly because of our limited understanding of physiological adaptations and thresholds. Even though some shallow water species have been investigated physiologically, community-scale studies on the effects of multiple stressors related to ongoing environmental change, including temperature rise, ocean acidification, and shifts in deposition of phytoplankton, are completely unknown for deep-sea organisms. Thus, the establishment of long-term and coordinated monitoring programs, such as those rapidly growing under the umbrella of the Southern Ocean Observing System (SOOS) or the Deep Ocean Observing Strategy (DOOS), may represent unique tools for measuring the status and trends of deep-sea and SO ecosystems
Mirror seeing of the Antarctic survey telescope
Get PDFSite testing results indicate that Antarctic Dome A is an excellent ground-based astronomical site suitable for observations ranging from visible to infrared wavelengths. However, the harsh environment in Antarctica, especially the very low temperature and atmospheric pressure, always produces frost on the telescopes’ mirrors, which are exposed to the air. Since the Dome A site is still unattended, the Antarctic telescope tubes are always designed to be filled with dry nitrogen, and the outer surfaces of the optical system are heated by an indium-tin oxide thin film. These precautions can prevent the optical surfaces from frosting over, but they degrade the image quality by introducing additional mirror seeing. Based on testing observations of the second Antarctic Survey Telescope (AST3-2) in the Mohe site in China, mirror seeing resulting from the heated aspheric plate has been measured using micro-thermal sensors. Results comparing the real-time atmospheric seeing monitored by the Differential Image Motion Monitor and real-time examinations of image quality agree well
Using the physical decomposition method to study the effects of Arctic factors on wintertime temperatures in the Northern Hemisphere and China
Get PDFThe physical decomposition method separates atmospheric variables into four parts, correlating each with solar radiation, land–sea distribution, and inter-annual and seasonal internal forcing, strengthening the anomaly signal and increasing the correlation between variables. This method was applied to the reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), to study the effects of Arctic factors (Arctic oscillation (AO) and Arctic polar vortex) on wintertime temperatures in the Northern Hemisphere and China. It was found that AO effects on zonal average temperature disturbance could persist for 1 month. In the AO negative phase in wintertime, the temperatures are lower in the mid–high latitudes than in normal years, but higher in low latitudes. When the polar vortex area is bigger, the zonal average temperature is lower at 50°N. Influenced mainly by meridional circulation enhancement, cold air flows from high to low latitudes; thus, the temperatures in Continental Europe and the North American continent exhibit an antiphase seesaw relationship. When the AO is in negative phase and the Arctic polar vortex larger, the temperature is lower in Siberia, but higher in Greenland and the Bering Strait. Influenced by westerly troughs and ridges, the polar air disperses mainly along the tracks of atmospheric activity centers. The AO index can be considered a predictor of wintertime temperature in China. When the AO is in negative phase or the Asian polar vortex is intensified, temperatures in Northeast China and Inner Mongolia are lower, because under the influence of the Siberia High and northeast cold vortex, the cold air flows southwards
Linkages between Arctic sea ice cover, large-scale atmospheric circulation, and weather and ice conditions in the Gulf of Bothnia, Baltic Sea
Get PDFDuring years 1980/1981–2012/2013, inter-annual variations in sea ice and snow thickness in Kemi, in the northern coast of the Gulf of Bothnia, Baltic Sea, depended on the air temperature, snow fall, and rain. Inter-annual variations in the November—April mean air temperature, accumulated total precipitation, snow fall, and rain, as well as ice and snow thickness in Kemi and ice concentration in the Gulf of Bothnia correlated with inter-annual variations of the Pacific Decadal Oscillation (PDO), Arctic Oscillation (AO), North Atlantic Oscillation (NAO), Scandinavian Pattern (SCA), and Polar / Eurasian Pattern (PEU). The strong role of PDO is a new finding. In general, the relationships with PDO were approximately equally strong as those with AO, but rain and sea ice concentration were better correlated with PDO. The correlations with PDO were, however, not persistent; for a study period since 1950 the correlations were much lower. During 1980/1981—2012/2013, also the Pacific / North American Pattern (PNA) and El Nino–Southern Oscillation (ENSO) had statistical connections with the conditions in the Gulf of Bothnia, revealed by analyzing their effects combined with those of PDO and AO. A reduced autumn sea ice area in the Arctic was related to increased rain and total precipitation in the following winter in Kemi. This correlation was significant for the Pan-Arctic sea ice area in September, October, and November, and for the November sea ice area in the Barents / Kara seas
Statistical characteristics of ionospheric backscatter observed by SuperDARN Zhongshan radar in Antarctica
Get PDFZhongshan HF radar, as one component of SuperDARN, has been established and in operation since April, 2010. Using data from the first two years of its operation, this paper investigates the radar’s performance, the diurnal and seasonal variations of ionospheric echoes, and their dependence on geomagnetic activity. Statistical studies show that the occurrence of echoes in different beams varies at different frequencies, which arises from the direction of the beam and the area over which the beam can achieve the orthogonality condition between the wave vector and the Earth’s magnetic field. The diurnal variation is obvious with double peak structures both in the occurrence rate and average power at 04–08 UT and 16–17 UT. The line-of-sight velocities are mainly positive on the dayside and negative on the nightside for Beam 0, which is the opposite of the trend for Beam 15. The spectral widths on the dayside are often higher than those on the nightside owing to the high energy particle precipitation in the cusp region. The seasonal variations are more obvious for those beams with larger numbers. The occurrence, the average power, the line-of-sight velocity, and the spectral widths are generally larger in the winter months than in the summer months. The influence of geomagnetic activity on radar echoes is significant. The peak echo occurrence appears on the dayside during geomagnetically quiet times, and shifts toward the nightside and exhibits an obvious decrease with increasing Kp. With increasing geomagnetic activity, the line-of-sight velocities increase, whereas the spectral widths decrease. The frequency dependence is investigated and it is found that in the operating frequency bands in 2010, 9–10 MHz is the most appropriate band for the SuperDARN Zhongshan
radar
Modeling Arctic Intermediate Water: The effects of Neptune parameterization and horizontal resolution
Get PDFArctic Intermediate Water (AIW), advected from the North Atlantic Ocean, has a potential influence on climate in the Arctic region, but is poorly simulated in coarse resolution models. In this study, a coupled ice-ocean model is used to investigate features of AIW by conducting two sensitivity experiments based on Neptune parameterization and horizontal resolution. The results show that both experiments improve the modeling of temperature profiles in the western Eurasian Basin, mainly as a result of more realistic volume and heat transport through the Fram Strait. Topographical flows are well reproduced using Neptune parameterization or a finer horizontal resolution. In the eddy-permitting model with relatively higher resolution, the velocity field is more realistic than in the Neptune parameterization model, and complex inflow and outflow belts of barotropic structure are well reproduced. The findings of this study suggest that increased model resolution, as provided by an eddy-resolving model, is needed to reproduce realistic circulation and thermohaline structure in the Arctic, since the Rossby radius of deformation is only several kilometers in the Arctic Ocean. This paper focuses on the external heat input rather than internal mixing process, and obtains a conclusion that the heat input from the Fram Strait is a main factor to reproduce AIW in the Eurasian Basin successfully, at least for the western part
Monitoring the Amery Ice Shelf front during 2004−2012 using ENVISAT ASAR data
Get PDFThe Amery Ice Shelf is the largest ice shelf in East Antarctica. It drains continental ice from an area of more than one million square kilometres through a section of coastline that represents approximately 2% of the total circumference of the Antarctic continent. In this study, we used a time series of ENVISAT ASAR images from 2004–2012 and flow lines derived from surface velocity data to monitor the changes in 12 tributaries of the Amery Ice Shelf front. The results show that the Amery Ice Shelf has been expanding and that the rates of expansion differ across the shelf. The highest average annual rate of advance from 2004–2012 was 3.36 m∙d-1 and the lowest rate was 1.65 m∙d-1. The rates in 2009 and 2010 were generally lower than those in other years. There was a low correlation between the rate of expansion and the atmospheric temperature recorded at a nearby research station, however the mechanism of the relationship was complex. This study shows that the expansion of the Amery Ice Shelf is slowing down, reflecting a changing trend in climate and ice conditions in East Antarctica
Structure and seasonal changes in atmospheric boundary layer on coast of the east Antarctic continent
Get PDFThe temperature, humidity, and vertical distribution of ozone in the Antarctic atmospheric boundary layer(ABL) and their seasonal changes are analyzed, by using the high-resolution profile data obtained during the International Polar Year 2008 to 2009 at Zhongshan Station, to further the understanding of the structure and processes of the ABL. The results show that the frequency of the convective boundary layer in the warm season accounts for 84% of its annual occurrence frequency. The frequency of the stable boundary layer in the cold season accounts for 71% of its annual occurrence frequency. A neutral boundary layer appears rarely. The average altitude of the convective boundary layer determined by the parcel method is 600 m; this is 200 to 300 m higher than that over inland Antarctica. The average altitude of the top of the boundary layer determined by the potential temperature gradient and humidity gradient is 1 200 m in the warm season and 1 500 m in the cold season. The vertical structures of ozone and specific humidity in the ABL exhibit obvious seasonal changes. The specific humidity is very high with greater vertical gradient in the warm season and very low with a lesser gradient in the cold season under 2 000 m. The atmospheric ozone in the ABL is consumed by photochemical processes in the warm season, which results in a slight difference in altitude. The sub-highest ozone center is located in the boundary layer, indicating that the ozone transferred from the stratosphere to the troposphere reaches the low boundary layer during October and November in Antarctica
AES Executive Summary
Get PDFEnergy is a fundamental component of sustainable development and is a crucial element of both human development and economic activity, balanced against protection of the environment and respect for traditional ways of living. The Arctic is full of energy resources – from oil and gas to renewable resources such as wind, solar, hydrokinetic and geothermal – yet peoples of the Arctic pay some of the highest energy prices in the world.
To take advantage of great energy and resource wealth potential, policy makers, community leaders and the private sector must work together to develop resources safely, facilitate access to affordable energy, and develop policies balancing risk mitigation, cultural integrity and economic opportunity. The Arctic is poised to take advantage of a changing market in a changing world; however, it is clear the region faces many daunting obstacles.
This dilemma provides the context for the Arctic Energy Summit’s themes of Richness, Resilience and Responsibility. Moving forward, we must understand the challenges and difficulties associated with developing great energy wealth and seek to ensure this development is done for the benefit of Northern peoples. The Summit’s sessions delivered a variety of perspectives and guidance for the future, namely responsible development and utilization of Arctic energy resources have great potential to spur community and economic resilience
Evaluation of reanalysis and satellite-based sea surface winds using in situ measurements from Chinese Antarctic Expeditions
Get PDFSea surface winds from reanalysis (NCEP-2 and ERA-40 datasets) and satellite-based products (QuikSCAT and NCDC blended sea winds) are evaluated using in situ ship measurements from the Chinese National Antarctic Research Expeditions (CHINAREs) from 1989 through 2006, with emphasis on the Southern Ocean (south of 45°S). Compared with ship observations, the reanalysis winds have a positive mean bias (0.32 m∙s-1 for NCEP-2 and 0.13 m∙s-1 for ERA-40), and this bias is more pronounced in the Southern Ocean (0.57 m∙s-1 and 0.45 m∙s-1, respectively). However, mean biases are negative in the tropics and subtropics. The satellite-based winds also show positive mean biases, larger than those of the reanalysis data. All four wind products overestimate ship wind speed for weak winds (10 m∙s-1). Differences between the reanalysis and satellite winds are examined to identify regions with large discrepancies