The rapid ongoing changes in the Central Arctic Ocean call for baseline information on the pelagic fauna. However, sampling for motile organisms which…The rapid ongoing changes in the Central Arctic Ocean call for baseline information on the pelagic fauna. However, sampling for motile organisms which easily escape vertically towed nets is challenging. Here, we report the species composition and catch weight of pelagic fishes and larger zooplankton from 12 trawl hauls conducted in ice covered waters in the Central Arctic Ocean beyond the continental slopes in late summer. Combined trawl catches with acoustics data revealed low amounts of fish and zooplankton from the advective influenced slope region in the Nansen Basin in the south to the ice-covered deep Amundsen Basin in the north. Both arctic and subarctic-boreal species, including the ones considered as Atlantic expatriate species were found all the way to 87.5o N. We found three fish species (Boreogadus saida, Benthosema glaciale and Reinhardtius hippoglossoides), but the catch was limited to only seven individuals. Euphausiids, amphipods and gelatinous zooplankton dominated the catch weight in the Nansen Basin in the mesopelagic communities. Euphausiids were almost absent in the Amundsen Basin with copepods, amphipods, chaetognaths and gelatinous zooplankton dominating. We postulate asymmetric conditions in the pelagic ecosystems of the western and eastern Eurasian Basin caused by ice and ocean circulation regimes.more
The sea ice extent and sea ice thickness in the Arctic Ocean have declined consistently in the last decades. The loss of sea ice as well as warmer inf…The sea ice extent and sea ice thickness in the Arctic Ocean have declined consistently in the last decades. The loss of sea ice as well as warmer inflowing Atlantic Water have major consequences for the Arctic Ocean heat content and the watermasses flowing out from the Arctic. Sustained observations from ocean moorings show that the upper ocean temperature across the Arctic outflow with the East Greenland Current in the Fram Strait has increased significantly between 2003 and 2019. Polar Water contains more heat in summer due to lower sea ice concentration and longer periods of open water upstream. Warm returning Atlantic Water has a greater presence in the central Fram Strait in winter since 2015, impacting winter sea ice thickness and extent. Combined, these processes result in a reduced sea ice cover downstream along the whole east coast of Greenland with inevitable consequences for winter-time ocean convection and ecosystem functioning.more
Global Navigation Satellite System (GNSS) Radio Occultation (RO) is an active limb sounding technique, where GNSS satellites transmitted signals passi…Global Navigation Satellite System (GNSS) Radio Occultation (RO) is an active limb sounding technique, where GNSS satellites transmitted signals passing through the atmosphere of the Earth and received by a GNSS receiver on low earth orbiter (LEO) satellite. RO provides accurate atmospheric refractivity profile. RO technique has been widely used to study the atmosphere of planets. This paper investigates the use of GNSS RO for tropopause height (TPH) estimation as one of the key climate parameters over Egypt. TPH is also very important in determining the wet delay in GNSS analysis. Two years (2016 and 2017) of MetOP A and B satellites data are used. ROPP software package is used in the analysis. For validation of the results, RO-derived TPH is compared with European Centre for Medium-Range Weather Forecast (ECMWF) model as well as radiosonde (RS). Good agreement and high correlation are found between TPH from RO and ECMWF and RS on the other hand. TPH varies between 14 and 16 km over Egypt. It decreases with latitude and shows no clear trend with longitude. Tropopause temperature is found to increase with latitude.more