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  • 1
    Call number: AWI A4-20-93991
    Description / Table of Contents: Over the last decades, the Arctic regions of the earth have warmed at a rate 2–3 times faster than the global average– a phenomenon called Arctic Amplification. A complex, non-linear interplay of physical processes and unique pecularities in the Arctic climate system is responsible for this, but the relative role of individual processes remains to be debated. This thesis focuses on the climate change and related processes on Svalbard, an archipelago in the North Atlantic sector of the Arctic, which is shown to be a "hotspot" for the amplified recent warming during winter. In this highly dynamical region, both oceanic and atmospheric large-scale transports of heat and moisture interfere with spatially inhomogenous surface conditions, and the corresponding energy exchange strongly shapes the atmospheric boundary layer. In the first part, Pan-Svalbard gradients in the surface air temperature (SAT) and sea ice extent (SIE) in the fjords are quantified and characterized. This analysis is based on observational data from meteorological stations, operational sea ice charts, and hydrographic observations from the adjacent ocean, which cover the 1980–2016 period. [...]
    Type of Medium: Dissertations
    Pages: xv, 123 Seiten , Illustrationen, Diagramme
    Language: English
    Note: Dissertation, Universität Potsdam, 2019 , CONTENTS 1 Introduction 1.1 Context: A rapidly changing Arctic 1.1.1 Documentation of recent changes in the Arctic 1.1.2 Research relevance 1.1.3 Objective: Svalbard as a hotspot for climate change 1.2 Physical Background 1.2.1 Radiation and surface energy balance 1.2.2 Peculiarities of the Arctic climate system 1.2.3 Role of atmospheric circulation 1.3 The regional setup on Svalbard 2 data and methods 2.1 Data description 2.1.1 Era-Interim atmospheric reanalysis 2.1.2 Svalbard Station Meteorology 2.1.3 Sea Ice Extent 2.1.4 Ocean data products 2.1.5 FLEXTRA Trajectories 2.2 Statistical Methods 2.2.1 Trend estimation 2.2.2 Correlation 2.2.3 Coefficient of Determination 3 state of surface climate parameters: pan-svalbard differences 3.1 Motivation 3.2 Surface air temperature 3.2.1 Annual cycle 3.2.2 Annual temperature range 3.2.3 Long-term trends 3.3 Fjord Sea Ice coverage 3.3.1 Climatology 3.3.2 Sea ice cover trends 3.3.3 Regional classification across Svalbard 3.3.4 Drivers of regional differences 3.4 Discussion and Conclusion 3.5 Current state of climate projections for the Svalbard region 4 Air mass back trajectories 4.1 Methodology 4.2 Winter 4.2.1 Source Regions of Ny-Ålesund Air 4.2.2 Circulation changes 4.2.3 Quantification of Advective Warming 4.3 Summer 4.3.1 Source Regions of Ny-Ålesund Air 4.3.2 Circulation changes 4.3.3 Quantification of advective cooling 4.3.4 Observational Case Study: May/June 2017 4.4 Discussion and Conclusion 5 Changing drivers of the arctic near surface temperature budget 5.1 Winter 5.2 Summer 5.3 Summary 6 Summary and conclusion A Details on calculations A.1 SLP composite Index A.2 Derivation of coefficient of determination A.3 Temperature effect of changing source regions over time B Supplementary figures Bibliography
    Location: AWI Reading room
    Branch Library: AWI Library
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  • 2
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  • 4
    Publication Date: 2018-10-04
    Description: Arctic amplification of climate warming is caused by various feedback processes in the atmosphere-ocean-ice system, and yields the strongest temperature increase during winter in the Arctic North Atlantic region. Located in this key region, Svalbard is affected by increasing winter cyclone activity associated with warm and moist air advection from lower latitudes. In our study, we attempt to quantify the advective contribution to the recent observed atmospheric winter warming in the Svalbard area (1996 - 2016). Based on Ny-Ålesund radiosonde measurements during winter, a strong dependence of the tropospheric temperature on the synoptic flow direction is identified. Using FLEXTRA air backward trajectories, an increase in occurrence frequency of air with origin in the lower latitude Atlantic region is found, that is attributed to a change in atmospheric circulation patterns involving an intensified Icelandic low and a pronounced Ural blocking high. Both the Scandinavian blocking and the Ural blocking high seem to play an important role in the context of advecting air from lower latitudes towards the Svalbard region, therefore our study is of particular relevance for aerosol and trace gas transport, and according measurements on Svalbard . Beyond that, the enhanced occurrence of the Ural blocking in the recent decade has been linked to sea ice retreat in the Barents/Kara Seas. Given that this link is robust, it would directly feed back on additional sea ice retreat in the region due both to anomalous advection of warm air masses from the south and mechanically pushing pack ice more northward, leaving more open water surfaces along the Svalbard coast. Regarding the circulation changes, we find that about one quarter (0.45 K per decade) of the observed tropospheric winter warming trend in the North Atlantic region of the Arctic (2 K per decade) is due to increased advection of warm and moist air from the lower latitude Atlantic region. Furthermore, the Ny-Ålesund radiosonde data evidence that the corresponding warming footprint extends significantly from the surface throughout the entire troposphere, with a vertically constant relative contribution to the overall warming. Essentially, the climate of the Svalbard region as center of the strongest recent winter warming is found to be particularly sensitive to changes in the atmospheric circulation compared to other regions of the Arctic.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 5
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    In:  (Bachelor thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 29 pp
    Publication Date: 2013-04-19
    Keywords: Course of study: BSc Physics of the Earth System
    Type: Thesis , NonPeerReviewed
    Format: text
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  • 6
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    In:  (Master thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 71 pp
    Publication Date: 2016-09-12
    Keywords: Course of study: MSc Climate Physics
    Type: Thesis , NonPeerReviewed
    Format: text
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  • 7
    Publication Date: 2020-01-21
    Description: Landfast sea ice covers the inner parts of Kongsfjorden, Svalbard, for a limited time in winter and spring months, being an important feature for the physical and biological fjord systems. Systematic fast-ice monitoring for Kongsfjorden, as a part of a long-term project at the Norwegian Polar Institute (NPI) was started in 2003, with some more sporadic observations from 1997 to 2002. It includes the ice extent mapping and in situ measurements of ice and snow thickness, and freeboard at several sites in the fjord. The permanent presence of NPI personnel in Ny-Ålesund Research Station enables regular in situ fast-ice thickness measurements as long as the fast ice is accessible. Further, daily visits to the observatory on the mountain Zeppelinfjellet close to Ny-Ålesund, allow regular ice extent observations (weather, visibility, and daylight permitting). Data collected within this standardized monitoring programme have contributed to a number of studies. Monitoring of the sea-ice conditions in Kongsfjorden can be used to demonstrate and investigate phenomena related to climate change in the Arctic.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , NonPeerReviewed
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  • 8
    Publication Date: 2020-03-05
    Description: Over the recent decades, temperature increase in the Arctic has been almost twice as large as the global average. This amplification of global warming is attributed to various feedback mechanisms present in the Arctic environment. Some processes are locally confined to the diminishing sea ice cover of the Arctic ocean, particularly the sea ice – albedo effect during polar day. Other amplifying processes related to the increasing open water surface of the Arctic ocean include e.g. the increasing heat flux from the ocean to the atmosphere. The resulting latent heat flux and augmenting evaporation contribute to an increasing atmospheric moisture content, which affects the longwave downward radiation directly or via changing cloud microphysics. Furthermore, atmospheric moisture and heat are more frequently advected from lower latitudes into the Arctic in relation to changes in the atmospheric circulation. During the dark period of polar night, the Arctic warming trend is not homogenously distributed over the polar cap, but occurs strongest at the surface in the Barents / Kara Seas and in the free troposphere of the Arctic North Atlantic sector. Thus, Svalbard is located in a key region of climate change. Observations from Ny-Ålesund at the west coast of the Svalbard archipelago show an annual temperature increase of 1.4 K per decade since the 1990s, with an average temperature that by now exceeds those observed during the early Arctic warming period in the 1920 to 1940s. The recent winter warming is even twice as high, and is accompanied by an increase in atmospheric moisture. Surface radiation observations in winter further indicate a change in cloudiness along with an increase in net longwave radiation. Although the winter warming is bottom-amplified, radiosonde observations show that the increasing temperature signal occurs over the entire troposphere. Indeed, part of the Svalbard winter warming is associated with enhanced warm and moist air advection in the free troposphere caused by increased cyclonic activity related to changes in atmospheric circulation patterns. The various processes contributing to Arctic amplification of climate warming link the local observations from Ny-Ålesund with processes occurring both in the Arctic and in the northern hemispheric mid-latitudes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 9
    Publication Date: 2020-03-05
    Description: The two concerted field campaigns, Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD) and the Physical feedbacks of Arctic planetary boundary level Sea ice, Cloud and AerosoL (PASCAL), took place near Svalbard from 23 May to 26 June 2017. They were focused on studying Arctic mixed-phase clouds and involved observations from two airplanes (ACLOUD), an icebreaker (PASCAL) and a tethered balloon, as well as ground-based stations. Here, we present the synoptic development during the 35-day period of the campaigns, using near-surface and upper-air meteorological observations, as well as operational satellite, analysis, and reanalysis data. Over the campaign period, short-term synoptic variability was substantial, dominating over the seasonal cycle. During the first campaign week, cold and dry Arctic air from the north persisted, with a distinct but seasonally unusual cold air outbreak. Cloudy conditions with mostly low-level clouds prevailed. The subsequent 2 weeks were characterized by warm and moist maritime air from the south and east, which included two events of warm air advection. These synoptical disturbances caused lower cloud cover fractions and higher-reaching cloud systems. In the final 2 weeks, adiabatically warmed air from the west dominated, with cloud properties strongly varying within the range of the two other periods. Results presented here provide synoptic information needed to analyze and interpret data of upcoming studies from ACLOUD/PASCAL, while also offering unprecedented measurements in a sparsely observed region.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 10
    Publication Date: 2020-03-05
    Description: Arctic Amplification of climate warming is caused by various feedback processes in the atmosphere-ocean-ice system and yields the strongest temperature increase during winter in the Arctic North Atlantic region. In our study, we attempt to quantify the advective contribution to the observed atmospheric warming in the Svalbard area. Based on radiosonde measurements from Ny-Ålesund, a strong dependence of the tropospheric temperature on the synoptic flow direction is revealed. Using FLEXTRA backward trajectories, an increase of advection from the lower latitude Atlantic region towards Ny-Ålesund is found that is attributed to a change in atmospheric circulation patterns. We find that about one-quarter (0.45 K per decade) of the observed atmospheric winter near surface warming trend in the North Atlantic region of the Arctic (2 K per decade) is due to increased advection of warm and moist air from the lower latitude Atlantic region, affecting the entire troposphere.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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