ALBERT

Description: K-Ar ages of 82 slate and schist (white-mica-rich whole-rock) samples are reported for Late Precambrian-Early Ordovician metamorphic rocks of the Wilson, Bowers and Robertson Bay terranes of northern Victoria Land. These are amalgamated in two vertical sections along composite NE-SW horizontal profiles across (1) Oates Coast in the north, and (2) Terra Nova Bay area in the south. The ages are in the range 328517 Ma. Both profiles show some age variation with altitude, but more importantly, they define an inverted wedge shaped pattern, reflecting a pop-up structure. This is oriented NW-SE at the eastern margin of the Wilson terrane, and the edges coincide with the Exiles and Wilson Thrusts which cross the region. Ages inside the pop-up structure are younger, ca. 460480 Ma, than those along its eastern and western flanks, ca. 490520 Ma. The K-Ar age patterns thus demonstrate a late Ross Orogenic age (ca. 460 Ma) for this structure, which may be associated with assembly of the Wilson and Bowers terranes.

Description: Because measurements of bromine at high latitudes are scarce, the current understanding of bromine chemistry is largely based on model calculations. In order to help quantify the amount of bromine in the atmosphere, we measured BrO columns with two ground-based UV-visible spectrometers at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80oN, 86oW) in spring 2008. One of these instruments, the UT-GBS (University of Toronto Ground-Based Spectrometer), has been deployed at Eureka during polar sunrise since 1999. The other instrument, the PEARL-GBS (PEARL Ground-Based Spectrometer), was installed permanently in Eureka in August 2006 for year-round operation.The small signal and large diurnal variation of BrO are challenges for ground-based BrO retrievals. With zenith-sky measurements, we can retrieve vertical column densities of BrO, which are primarily sensitive to the stratosphere. We will discuss different methods for these retrievals and will compare our ground-based BrO vertical column density measurements with Ozone Monitoring Instrument on board the NASA Earth Observing System Aura satellite. Additionally, we are working on techniques to retrieve tropospheric partial columns of BrO using a combination of direct-sun measurements and zenith-sky measurements. We will discuss the status of these retrievals and future plans for tropospheric BrO measurements at Eureka.

Description: Despite its low concentrations in the atmosphere, bromine monoxide (BrO) accounts for up to half of springtime catalytic ozone depletion in the stratosphere. In the troposphere, large quantities of BrO can appear suddenly and linger for several days. These bromine explosions have been linked to mercury deposition in the Arctic.Retrieval of BrO is difficult and measurements of bromine species at high latitudes are scarce. Therefore, there are large uncertainties in our knowledge of the amount of bromine in the atmosphere. In order to improve this situation, we measured BrO columns with two ground-based UV-visible spectrometers at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80oN, 86oW) in spring 2008. This research is an integral part the larger CANDAC (Canadian Network for the Detection of Atmospheric Change) project at PEARL to study Arctic atmospheric processes through 2007-2009, the International Polar Year (IPY), and beyond.We will discuss the techniques and challenges for ground-based BrO measurements. Furthermore, we will discuss comparisons between the ground-based measurements of BrO above Eureka and those made by the OSIRIS and OMI satellite instruments, distinguishing between tropospheric and stratospheric BrO concentrations.

Description: Regional variations in seasonal mean Indian summer monsoon rainfall and circulation for the period 1979–2009 are investigated using multiple data products. The focus is on four separate regions: the Western Ghats (WG), the Ganges basin (GB), the Bay of Bengal (BB), and Bangladesh–northeastern India (BD). Data reliability varies strongly by region, with particularly low correlations between different products for the BB and BD regions. Correlations between regions are generally not statistically significant, indicating rainfall varies independently in these four regions. The diagnosed associations between rainfall, circulation, and sea surface temperatures can be sensitive to the choice of rainfall product, and multiple precipitation products may need to be analyzed in this region to ensure that the results are robust. Enhanced precipitation in the BD region is associated with anomalous anticyclonic circulation at 850 mb and westerly anomalies along the foothills of the Tibetan Plateau, while precipitation in the other regions is associated with cyclonic flow and easterlies. These associations provide a dynamical explanation for previously reported weak, negative correlations between BD and the other regions. In addition to observed products, atmosphere-only simulations made using the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) during Project Athena are analyzed. While the simulations do not reproduce the observed interannual variations in rainfall, the fidelity of the simulated precipitation and circulation structure is comparable to or even outperforms the different state-of-the-art reanalysis products considered. Accuracy in representing interannual variability and regional structure thus appears to be independent.

Description: In spring 2011, the Arctic polar vortex was stronger than in any other year on record. As the polar vortex started to break up in April, ozone and NO2 columns were measured with UV-visible spectrometers above the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Canada (80.05° N, 86.42° W) using the differential optical absorption spectroscopy (DOAS) technique. These ground-based column measurements were complemented by Ozone Monitoring Instrument (OMI) and Optical Spectrograph and Infra-Red Imager System (OSIRIS) satellite measurements, Global Modeling Initiative (GMI) simulations, and meteorological quantities. On 8 April 2011, NO2 columns above PEARL from the DOAS, OMI, and GMI datasets were approximately twice as large as in previous years. On this day, temperatures and ozone volume mixing ratios above Eureka were high, suggesting enhanced chemical production of NO2 from NO. Additionally, GMI NOx (NO + NO2) and N2O fields suggest that downward transport along the vortex edge and horizontal transport from lower latitudes also contributed to the enhanced NO2. The anticyclone that transported lower-latitude NOx above PEARL became frozen-in and persisted in dynamical and GMI N2O fields until the end of the measurement period on 31 May 2011. Ozone isolated within this frozen-in anticyclone (FrIAC) in the middle stratosphere was lost due to reactions with the enhanced NOx. Below the FrIAC (from the tropopause to 700 K), NOx driven ozone loss above Eureka was larger than in previous years, according to GMI monthly average ozone loss rates. Using the passive tracer technique, with passive ozone profiles from the Lagrangian Chemistry and Transport Model, ATLAS, ozone losses since 1 December 2010 were calculated at 600 K. In the air mass that was above Eureka on 20 May 2011, ozone losses reached 4.2 parts per million by volume (ppmv) (58%) and 4.4 ppmv (61%), when calculated using GMI and OSIRIS ozone profiles, respectively. This gas-phase ozone loss led to a more rapid decrease in ozone column amounts above Eureka in April/May 2011 compared with previous years. Ground-based, OMI, and GMI ozone total columns all decreased by more than 100 DU from 15 April to 20 May. Two lows in the ozone columns were also investigated and were attributed to a vortex remnant passing above Eureka at ~500 K on 12/13 May and an ozone mini-hole on 22/23 May.

Description: Unusually cold conditions in Arctic winter 2010/11 led to large stratospheric ozone loss. We investigate this with UV-visible measurements made at Eureka, Canada (80.05°N, 86.42°W) from 1999–2011. For 8–22 March 2011, OClO was enhanced, indicating chlorine activation above Eureka. Ozone columns were lower than in any other year in the record, reaching minima of 237 DU and 247 DU in two datasets. The average NO2 column inside the vortex, measured at visible and UV wavelengths, was 46 ± 30% and 45 ± 27% lower in 2011 than the average NO2column from previous years. Ozone column loss was estimated from two ozone datasets, using a modeled passive ozone tracer. For 12–20 March 2011, the average ozone loss was 27% and 29% (99 DU and 108 DU). The largest percent ozone loss in the 11-year record of 47% (250 DU and 251 DU) was observed on 5 April 2011.