Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Atmospheric energy transport in spring of years with low September sea-ice extent
Stockholm University, Faculty of Science, Department of Meteorology .
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A significant change in Arctic climate is the declining trend of September sea ice. However, large year-to-year variations are superimposed on this trend. Understanding this variability is important for understanding processes contributing to the long-term decline and for seasonal sea-ice predictions, which become increasingly important for a range of activities in an emerging ice-free Arctic summer. Previous studies suggested that the atmosphere plays a key role: transport of heat and moisture into the Arctic during spring enhances the incoming surface longwave radiation, thereby controling the initiation of the annual ice melt and setting the stage for the September ice minimum. Here we explore the atmospheric dynamics promoting advection of heat and moisture into the Arctic. We find that years with a low September sea-ice concentration (SIC) are characterized by periods of increased net surface longwave radiation (LWN) in spring, triggering an early melt onset. A set of atmospheric circulation patterns related to these episodes is identified that support transport of heat and moisture into the Arctic. The most dominant circulation patterns promote transport either from northern Russia and the Kara Sea or from the North Pacific; the latter resembles the so-called Arctic dipole anomaly. However, episodes of enhanced LWN also occur in years with high September SICs and are associated with similar atmospheric circulation patterns. Differences between years with low and high September SICs are not due to different spring processes resulting from different circulation patterns. Instead it is the duration and strength of these patterns that makes the difference. Years with low September SICs feature episodes that are consistently stronger and more persistent than years with high SICs.

Keyword [en]
Sea ice, Arctic, climate variability, atmospheric dynamics
National Category
Earth and Related Environmental Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
URN: urn:nbn:se:su:diva-119826OAI: oai:DiVA.org:su-119826DiVA: diva2:848597
Available from: 2015-08-25 Created: 2015-08-25 Last updated: 2016-01-29Bibliographically approved
In thesis
1. The atmospheric contribution to Arctic sea-ice variability
Open this publication in new window or tab >>The atmospheric contribution to Arctic sea-ice variability
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Arctic sea-ice cover plays an important role for the global climate system. Sea ice and the overlying snow cover reflect up to eight times more of the solar radiation than the underlying ocean. Hence, they are important for the global energy budget, and changes in the sea-ice cover can have a large impact on the Arctic climate and beyond. In the past 36 years the ice cover reduced significantly. The largest decline is observed in September, with a rate of more than 12% per decade. The negative trend is accompanied by large inter-annual sea-ice variability: in September the sea-ice extent varies by up to 27% between years. The processes controlling the large variability are not well understood. In this thesis the atmospheric contribution to the inter-annual sea-ice variability is explored. The focus is specifically on the thermodynamical effects: processes that are associated with a temperature change of the ice cover and sea-ice melt. Atmospheric reanalysis data are used to identify key processes, while experiments with a state-of-the-art climate model are conducted to understand their relevance throughout different seasons. It is found that in years with a very low September sea-ice extent more heat and moisture is transported in spring into the area that shows the largest ice variability. The increased transport is often associated with similar atmospheric circulation patterns. Increased heat and moisture over the Arctic result in positive anomalies of water vapor and clouds. These alter the amount of downward radiation at the surface: positive cloud anomalies allow for more longwave radiation and less shortwave radiation. In spring, when the solar inclination is small, positive cloud anomalies result in an increased surface warming and an earlier seasonal melt onset. This reduces the ice cover early in the season and allows for an increased absorption of solar radiation by the surface during summer, which further accelerates the ice melt. The modeling experiments indicate that cloud anomalies of similar magnitude during other seasons than spring would likely not result in below-average September sea ice. Based on these results a simple statistical sea-ice prediction model is designed, that only takes into account the downward longwave radiation anomalies or variables associated with it. Predictive skills are similar to those of more complex models, emphasizing the importance of the spring atmosphere for the annual sea-ice evolution.

Place, publisher, year, edition, pages
Stockholm: Department of Meteorology, Stockholm University, 2015. 30 p.
Keyword
Sea ice, Arctic, Climate Variability
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
urn:nbn:se:su:diva-119779 (URN)978-91-7649-228-4 (ISBN)
Public defence
2015-10-16, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2015-09-24 Created: 2015-08-24 Last updated: 2016-02-09Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Kapsch, Marie-Luise
By organisation
Department of Meteorology
Earth and Related Environmental Sciences

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 46 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf