U/Pb dating of detrital zircons from late Palaeozoic deposits of Bel’kovsky Island (New Siberian Islands): critical testing of Arctic tectonic models

Detrital zircon U/Pb ages provide new insights into the provenance of Upper Devonian–Permian clastic rocks of Bel’kovsky Island, within the New Siberian Islands archipelago. Based on these new data, we demonstrate that Upper Devonian–Carboniferous turbidites of Bel’kovsky Island were derived from Grenvillian, Sveconorwegian, and Timanian sources similar to those that fed Devonian–Carboniferous deposits of the Severnaya Zemlya archipelago and Wrangel Island and were probably located within Laurentia–Baltica. Detrital zircon ages from the lower Permian deposits of Bel’kovsky Island suggest a drastic change in provenance and show a strong affinity with the Uralian Orogen. Two possible models to interpret this shift in provenance are proposed. The first involves movement of these continental blocks from the continental margin of Laurentia–Baltica towards the Uralian Orogen during the late Carboniferous to Permian, while the second argues for long sediment transport across the Barents shelf.     

Controls on Arctic glacier-fed river water temperature

The impact of climate change on Arctic rivers is expected to be severe. There is therefore a need for greater understanding of Arctic river temperature processes. This study quantifies the spatio-temporal variability of water temperatures in the Kårsa River, Sweden. Water temperature was monitored over two summers within the main proglacial channel and within braids fed by different sources. Longitudinal and lateral temperature patterns were assessed in relation to prevailing hydro-meteorology. Temperature metrics in the main channel increased with distance downstream but were moderated by a large lake, while temperatures in the braids were dependent upon channel source. The high temperature standard deviation and inter-site differences within the braids highlight the importance of braided channels for creating thermal habitat heterogeneity. Temperatures were dependent on hydro-meteorological conditions, with sensitivity to air temperature maximized during cooler, rainy conditions. These results shed new light on Arctic river temperature patterns and their controlling processes.     

Observation of Filterable Bromine Variabilities During Arctic Tropospheric Ozone Depletion Events in High (1hour) Time Resolution

The halogen ions Br^- and Cl^- together with NO₃ ^-, SO₄ ⁼, MSA^- (methane sulfonate), Na⁺ and NH₄ ⁺ were analysed by ion chromatography in extracts of more than 800 aerosol cellulose filter samples taken at Ny Ålesund, Svalbard (79°N, 12°E) in spring 1996 (March 27 - May 16) within the European Union project ARCTOC (Arctic Tropospheric Ozone Chemistry). Anticorrelated variations between f-Br (filterable bromine, i.e. water soluble bromine species that can be collected by aerosol filters) and ozone within the arctic troposphere were evaluated at a resolution of 1 or 2 hours for periods with depleted ozone and 4 hours at normal ozone. A mean f-Br concentration of 11 ng m^-3 (0.14 nmol m^-3) was observed for the whole campaign, while maximum concentrations of 80 ng m^-3 (1 nmol m^-3) were detected during two total O₃-depletion events (O₃ drop to mixing ratios below the detection limit of < 2 ppb). Anticorrelation between f-Br and O₃ was also seen during minor O₃-depletion episodes (sudden drop in O₃ by at least 10 ppb, but O₃ still exceeding the detection limit) and even for ozone variations near its background level (40-50 ppb). A time lag of about 10 hours between the change of ozone and of f-Br concentrations could only be found during a total ozone depletion event, when f-Br reached its maximum values several hours after ozone was totally destroyed. Bromine oxide (BrO) concentrations, measured by DOAS (Differential Optical Absorption Spectroscopy), and f-Br showed a coincident variability during almost the entire campaign (except in the case of total O₃-loss). Frequently enhanced anthropogenic nitrate and sulphate concentrations were observed during O₃-depletion periods. At O₃ concentrations < 10 ppb sulphate and nitrate exceed their typical mean level by 54% and 77%, respectively. This may indicate a possible connection between acidity and halogen release.     

北极涛动年代际变化对东亚北部冬季气温增暖的影响

利用NCEP／NCAR再分析资料中的地表气温资料,分析了1949-1999年东亚北部地区冬季气温的变化。结果表明,从20世纪70年代中期开始东亚北部的气温显著升高,具有明显的年代际变化特征。这种气温的异常变化主要受东亚冬季风的直接影响。近二十几年来,北极涛动对东亚冬季风的影响越来越显著,北极涛动维持在正位相并持续增强,同期东亚冬季风持续减弱。研究表明,北极涛动持续增强的趋势是东亚北部地区冬季增暖的重要原因之一。     

Reactive Nitrogen Compounds at Spitsbergen in the Norwegian Arctic

Simultaneousindependent measurements of NO_y and NO_x(NO_x= NO + NO₂) by high-sensitivitychemiluminescence systems and of PAN (peroxyacetylnitrate) and PPN (peroxypropionyl nitrate) by GC-ECDwere made at Spitsbergen in the Norwegian Arcticduring the first half year of 1994. The average mixingratio of the sum of PAN and PPN (denoted PANs)increased from around 150 pptv in early winter to amaximum of around 500 pptv in late March, whereasepisodic peak values reached 800 pptv. This occurredsimultaneously with a maximum in ozone which increasedto 45–50 ppbv in March–April. The average NO_xmixing ratio was 27 pptv and did not show any cyclethrough the period. The NO_y mixing ratio showeda maximum in late March, while the difference betweenNO_y and PAN decreased during spring. This is anindication of the dominance of PAN in the NO_ybudget in the Arctic, but possible changes in theefficiency of the NO_y converter could alsocontribute to this. Although most PAN in theArctic is believed to be due to long range transport,the observations indicate local loss and formationrates of up to 1–2 pptv h^-1 in April–May.Measurements of carbonyl compounds suggest thatacetaldehyde was the dominant, local precursor ofPAN.Now at 1.     

A Possible Feedback Mechanism Involving the Arctic Freshwater,the Arctic Sea Ice,and the North Atlantic Drift

1. Introduction It is believed that the transport of freshwater intothe high northern oceans plays a major role in thecirculation in the Nordic Seas and the Atlantic (andpossibly the World) Ocean since it passes convectiveregimes of major importance to …     

一个观察北极涛动与北大西洋涛动关系的典型个例

北极涛动与大西洋涛动是否属同一气候变率模态一直是北极涛动动力学研究方面的一个颇具争议的话题。文中通过对"0801南方雪灾"期间及其前后北极涛动与北大西洋涛动异常及产生原因进行个例分析,对两者之间的关系进行了讨论。首先使用交叉子波变换与子波相关方法分析了两者的相位关系。发现在30—60天时间尺度上北极涛动与北大西洋涛动相位相差90°或-90°。而在10 20天这一尺度上北极涛动与北大西洋涛动具有大致相同的相位。对北极涛动及北大西洋涛动形成的动力过程及其在拉尼娜背景下各自特点的分析表明,这种不同尺度上位相关系的差异来自于波-流相互作用动力学的局域性。众所周知,北极涛动的3个活动中心的形成与分别位于北大西洋、北太平洋和北极平流层的3个波流相互作用中心有关。而北大西洋涛动则主要与位于北大西洋的波-流相互作用中心有关。拉尼娜事件的出现通过影响太平洋急流及行星尺度的准定常波从而进一步强化了30-60天时间尺度上北极涛动与北大西洋涛动的这种差异。这主要是因为太平洋急流或准定常行星波在对流层中直接影响了位于该区域的北极涛动的活动中心。同时准定常行星波冬季向上传播至平流层并与平流层极涡相互作用从而也影响了北极涛动在北极的活动中心。而在10—20天时间尺度上的北极涛动与北大西洋涛动同步关系则说明它们都是北极涛动的另一活动中心即大西洋上同一波-流相互作用现象——天气波破碎的反映。基于上述分析.文中倾向于认同将北极涛动和北大西洋涛动区别考虑的观点。     

Polar WRF模式海冰密集度方案对北极海雾模拟效果的个例研究

全球变暖的背景下,北极航线的常规通航甚至商业运营有望实现,而海雾会严重影响航道上船只的航行安全。海冰的存在使海气之间相互作用变得更为复杂,是研究北极海雾不可忽略的因素。船载观测发现,与中纬度常见平流冷却雾形成时气温下降速度往往超过海水降温速度不同,北极海雾发生时海冰的存在还会使海水降温速度超过空气降温速度。然而目前海冰分布是否会影响模式模拟海雾的准确性还不得而知,因此本文利用Polar WRF（Polar Weather Research and Forecasting）模式模拟了中国第七次北极考察中观测到的一次海雾过程,并进行海冰密集度敏感性试验。通过与船载观测和欧洲中期天气预报中心再分析数据比对发现,在低浮冰区内（海冰密集度小于50%）考虑海冰分布时可以更加准确地刻画潜热通量与水汽通量,模拟出与观测事实相符的表层空气降温与增湿过程以及相对湿度的变化,因此能够更好地刻画海雾的三维结构及其生消演变。     

Arctic hazes in summer over Greenland and the North American Arctic: II. Nature and concentrations of accumulation-mode and giant particles

Airborne measurements made during August 1985 over Greenland and its environs show that both accumulation-mode (0.1 m D2.0 m) and giant (D2 m) particles were present in relatively high concentrations in arctic haze layers and that the accumulation-mode particles dominated light scattering. Particles with diameters (D) between 1 and 4 m consisted predominately of mixed materials, small and dense inclusions, and probably organic compounds containing sulfur. Many of the particles from 0.1 to 1 m in diameter were also of mixed composition, with sulfuric acid, ammonium sulfate and organics probably the dominant constituents.     

Meteorology and haze structure during AGASP-II,Part 1: Alaskan Arctic flights, 2–10 April 1986

The second Arctic Gas and Aerosol Sampling Program (AGASP-II) was conducted across the Alaskan and Canadian Arctic in April 1986, to study the in situ aerosol, and the chemical and optical properties of Arctic haze. The NOAA WP-3D aircraft, with special instrumentation added, made six flights during AGASP-II. Measurements of wind, pressure, temperature, ozone, water vapor, condensation nuclei (CN) concentration, and aerosol scattering extinction (b_sp) were used to determine the location of significant haze layers. The measurements made on the first three flights, over the Arctic Ocean north of Barrow and over the Beaufort Sea north of Barter Island, Alaska are discussed in detail in this report of the first phase of AGASP II. In the Alaskan Arctic the WP-3D detected a large and persistent region of haze between 960 and 750 mb, in a thermally stable layer, on 2, 8, and 9 April 1986. At its most dense, the haze contained CN concentrations >10,000 cm^–3 and b_sp of 80×10^–6 m^–1 suggesting active SO₂ to H₂SO₄ gas-to-particle conversion. Calculations based upon observed SO₂ concentrations and ambient relative humidities suggest that 10⁴–10⁵ small H₂SO₄ droplets could have been produced in the haze layers. High concentrations of sub-micron H₂SO₄ droplets were collected in haze. Ozone concentrations were 5–10 ppb higher in the haze layers than in the surrounding troposphere. Outside the regions of haze, CN concentrations ranged from 100 to 400 cm^–3 and b_sp values were about (20–40)×10^–6 m^–1. Air mass trajectories were computed to depict the air flow upwind of regions in which haze was observed. In two cases the back trajectories and ground measurements suggested the source to be in central Europe.