| 1. |
- Smith, P B, et al.
(författare)
-
Cultural values, sources of guidance, and their relevance to managerial behavior - A 47-nation study
- 2002
-
Ingår i: Journal of Cross-Cultural Psychology. - : Sage Publications. - 0022-0221 .- 1552-5422. ; 33:2, s. 188-208
-
Tidskriftsartikel (refereegranskat)abstract
- Data are presented showing how middle managers in 47 countries report handling eight specific work events. The data are used to test the ability of cultural value dimensions derived from the work of Hofstede. Trompenaars, and Schwartz to predict the specific sources of guidance on which managers rely. Focusing on sources of guidance is expected to provide a more precise basis than do generalized measures of values for understanding the behaviors that prevail within different cultures. Values are strongly predictive of reliance on those sources of guidance that are relevant to vertical relationships within organizations. Hock ever, values are less successful in predicting reliance on peers and on more tacit sources of guidance. Explaining national differences in these neglected aspects of organizational processes will require greater sensitivity to the culture-specific contexts within which they occur.
|
|
| 2. |
- Graversen, Rune G., et al.
(författare)
-
Arctic amplification enhanced by latent energy transport of atmospheric planetary waves
- 2016
-
Ingår i: Quarterly Journal of the Royal Meteorological Society. - : Wiley. - 0035-9009 .- 1477-870X. ; 142:698, s. 2046-2054
-
Tidskriftsartikel (refereegranskat)abstract
- The atmospheric northward energy transport plays a crucial role for the Arctic climate; this transport brings to the Arctic an amount of energy comparable to that provided directly by the sun. The transport is accomplished by atmospheric waves-for instance large-scale planetary waves and meso-scale cyclones-and the zonal-mean circulation. These different components of the energy transport impact the Arctic climate differently. A split of the transport into stationary and transient waves constitutes a traditional way of decomposing the transport. However this procedure does not take into account the transport accomplished separately by the planetary and synoptic-scale waves. Here a Fourier decomposition is applied, which decomposes the transport with respect to zonal wave numbers. Reanalysis and model data reveal that the planetary waves impact Arctic temperatures much more than do synoptic-scale waves. In addition the latent transport by these waves affects the Arctic climate more than does the dry-static part. Finally, the EC-Earth model suggests that changes of the energy transport over the twentyfirst century will contribute to Arctic warming, despite the fact that in this model the total energy transport to the Arctic will decrease. This apparent contradictory result is due to the cooling induced by a decrease of the dry-static transport by planetary waves being more than compensated for by a warming caused by the latent counterpart.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Graversen, Rune G., et al.
(författare)
-
Polar Amplification in CCSM4 : Contributions from the Lapse Rate and Surface Albedo Feedbacks
- 2014
-
Ingår i: Journal of Climate. - 0894-8755 .- 1520-0442. ; 27:12, s. 4433-4450
-
Tidskriftsartikel (refereegranskat)abstract
- A vertically nonuniform warming of the troposphere yields a lapse rate feedback by altering the infrared irradiance to space relative to that of a vertically uniform tropospheric warming. The lapse rate feedback is negative at low latitudes, as a result of moist convective processes, and positive at high latitudes, due to stable stratification conditions that effectively trap warming near the surface. It is shown that this feedback pattern leads to polar amplification of the temperature response induced by a radiative forcing. The results are obtained by suppressing the lapse rate feedback in the Community Climate System Model, version 4 (CCSM4). The lapse rate feedback accounts for 15% of the Arctic amplification and 20% of the amplification in the Antarctic region. The fraction of the amplification that can be attributed to the surface albedo feedback, associated with melting of snow and ice, is 40% in the Arctic and 65% in Antarctica. It is further found that the surface albedo and lapse rate feedbacks interact considerably at high latitudes to the extent that they cannot be considered independent feedback mechanisms at the global scale.
|
|
| 6. |
- Graversen, Rune G., et al.
(författare)
-
Vertical structure of recent Arctic warming
- 2008
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 451:7174, s. 53-56
-
Tidskriftsartikel (refereegranskat)abstract
- Near-surface warming in the Arctic has been almost twice as large as the global average over recent decades1, 2, 3, 4, 5—a phenomenon that is known as the 'Arctic amplification'. The underlying causes of this temperature amplification remain uncertain. The reduction in snow and ice cover that has occurred over recent decades6, 7 may have played a role5, 8. Climate model experiments indicate that when global temperature rises, Arctic snow and ice cover retreats, causing excessive polar warming9, 10, 11. Reduction of the snow and ice cover causes albedo changes, and increased refreezing of sea ice during the cold season and decreases in sea-ice thickness both increase heat flux from the ocean to the atmosphere. Changes in oceanic and atmospheric circulation, as well as cloud cover, have also been proposed to cause Arctic temperature amplification12, 13, 14, 15, 16, 17. Here we examine the vertical structure of temperature change in the Arctic during the late twentieth century using reanalysis data. We find evidence for temperature amplification well above the surface. Snow and ice feedbacks cannot be the main cause of the warming aloft during the greater part of the year, because these feedbacks are expected to primarily affect temperatures in the lowermost part of the atmosphere, resulting in a pattern of warming that we only observe in spring. A significant proportion of the observed temperature amplification must therefore be explained by mechanisms that induce warming above the lowermost part of the atmosphere. We regress the Arctic temperature field on the atmospheric energy transport into the Arctic and find that, in the summer half-year, a significant proportion of the vertical structure of warming can be explained by changes in this variable. We conclude that changes in atmospheric heat transport may be an important cause of the recent Arctic temperature amplification.
|
|
| 7. |
- Graversen, Rune G., et al.
(författare)
-
Warm winds from the Pacific caused extensive Arctic sea-ice melt in summer 2007
- 2011
-
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 36:11-12, s. 2103-2112
-
Tidskriftsartikel (refereegranskat)abstract
- During summer 2007 the Arctic sea-ice shrank to the lowest extent ever observed. The role of the atmospheric energy transport in this extreme melt event is explored using the state-of-the-art ERA-Interim reanalysis data. We find that in summer 2007 there was an anomalous atmospheric flow of warm and humid air into the region that suffered severe melt. This anomaly was larger than during any other year in the data (1989-2008). Convergence of the atmospheric energy transport over this area led to positive anomalies of the downward longwave radiation and turbulent fluxes. In the region that experienced unusual ice melt, the net anomaly of the surface fluxes provided enough extra energy to melt roughly one meter of ice during the melting season. When the ocean successively became ice-free, the surface-albedo decreased causing additional absorption of shortwave radiation, despite the fact that the downwelling solar radiation was smaller than average. We argue that the positive anomalies of net downward longwave radiation and turbulent fluxes played a key role in initiating the 2007 extreme ice melt, whereas the shortwave-radiation changes acted as an amplifying feedback mechanism in response to the melt.
|
|
| 8. |
- Kapsch, Marie-Luise, et al.
(författare)
-
Summers with low Arctic sea ice linked to persistence of spring atmospheric circulation patterns
- 2019
-
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 52:3-4, s. 2497-2512
-
Tidskriftsartikel (refereegranskat)abstract
- The declining trend of Arctic September sea ice constitutes a significant change in the Arctic climate system. Large year-to-year variations are superimposed on this sea-ice trend, with the largest variability observed in the eastern Arctic Ocean. Knowledge of the processes important for this variability may lead to an improved understanding of seasonal and long-term changes. Previous studies suggest that transport of heat and moisture into the Arctic during spring enhances downward surface longwave radiation, thereby controlling the annual melt onset, setting the stage for the September ice minimum. In agreement with these studies, we find that years with a low September sea-ice concentration (SIC) are characterized by more persistent periods in spring with enhanced energy flux to the surface in forms of net longwave radiation plus turbulent fluxes, compared to years with a high SIC. Two main atmospheric circulation patterns related to these episodes are identified: one resembles the so-called Arctic dipole anomaly that promotes transport of heat and moisture from the North Pacific, whereas the other is characterized by negative geopotential height anomalies over the Arctic, favoring cyclonic flow from Siberia and the Kara Sea into the eastern Arctic Ocean. However, differences between years with low and high September SIC appear not to be due to different spring circulation patterns; instead it is the persistence and intensity of processes associated with these patterns that distinguish the two groups of anomalous years: Years with low September SIC feature episodes that are consistently stronger and more persistent than years with high SIC.
|
|
| 9. |
- Kapsch, Marie-Luise, 1985-
(författare)
-
The atmospheric contribution to Arctic sea-ice variability
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
| 10. |
- Kapsch, Marie-Luise, et al.
(författare)
-
The importance of spring atmospheric conditions for predictions of the Arctic summer sea ice extent
- 2014
-
Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 41:14, s. 5288-5296
-
Tidskriftsartikel (refereegranskat)abstract
- Recent studies have shown that atmospheric processes in spring play an important role for the initiation of the summer ice melt and therefore may strongly influence the September sea ice concentration (SSIC). Here a simple statistical regression model based on only atmospheric spring parameters is applied in order to predict the SSIC over the major part of the Arctic Ocean. By using spring anomalies of downwelling longwave radiation or atmospheric water vapor as predictor variables, correlation coefficients between observed and predicted SSIC of up to 0.5 are found. These skills of seasonal SSIC predictions are similar to those obtained using more complex dynamical forecast systems, despite the fact that the simple model applied here takes neither information of the sea ice state, oceanic conditions nor feedback mechanisms during summer into account. The results indicate that a realistic representation of spring atmospheric conditions in the prediction system plays an important role for the predictive skills of a model system.
|
|
| 11. |
- Mortin, Jonas, 1981-, et al.
(författare)
-
Evaluation of pan-Arctic melt-freeze onset in CMIP5 climate models and reanalyses using surface observations
- 2014
-
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 42:7-8, s. 2239-2257
-
Tidskriftsartikel (refereegranskat)abstract
- The seasonal melt-freeze transitions are fun- damental features of the Arctic climate system. The representation of the pan-Arctic melt and freeze onset (north of 60°N) is assessed in two reanalyses and eleven CMIP5 global circulation models (GCMs). The seasonal melt-freeze transitions are retrieved from surface air temperature (SAT) across the land and sea-ice domains and evaluated against surface observations. While monthly averages of SAT are reasonably well represented in models, large model-observation and model–model disparities of timing of melt and freeze onset are evident. The evaluation against surface observations reveals that the ERA-Interim reanalysis performs the best, closely followed by some of the climate models. GCMs and reanalyses capture the seasonal melt-freeze transitions better in the central Arctic than in the marginal seas and across the land areas. The GCMs project that during the 21st century, the summer length—the period between melt and freeze onset—will increase over land by about 1 month at all latitudes, and over sea ice by 1 and 3 months at low and high latitudes, respectively. This larger summer-length increase over sea ice at pro- gressively higher latitudes is related to a retreat of summer sea ice during the 21st century, since open water freezes roughly 40 days later than ice-covered ocean. As a consequence, by the year 2100, the freeze onset is projected to be initiated within roughly 10 days across the whole Arctic Ocean, whereas this transition varies by about 80 days today.
|
|
| 12. |
- Mortin, Jonas, 1981-, et al.
(författare)
-
Extending the QuikSCAT record of seasonal melt–freeze transitions over Arctic sea ice using ASCAT
- 2014
-
Ingår i: Remote Sensing of Environment. - : Elsevier BV. - 0034-4257 .- 1879-0704. ; 141:5, s. 214-230
-
Tidskriftsartikel (refereegranskat)abstract
- The seasonal melt–freeze transitions are important to continuously monitor over Arctic sea ice in order to better understand Arctic climate variability. The Ku-band scatterometer QuikSCAT (13.4 GHz), widely used to retrieve pan-Arctic seasonal transitions, discontinued its decadal long record in 2009. In this study, we show that the C-band scatterometer ASCAT (5.3 GHz), in orbit since 2006 and with an anticipated lifetime through 2021, can be used to extend the QuikSCAT record of seasonal melt–freeze transitions. This is done by (1) comparing back- scatter measurements over multiyear and first-year ice, and by (2) retrieving seasonal transitions from resolution-enhanced ASCAT and QuikSCAT measurements and comparing the results with independent datasets. Despite operating in different frequencies, ASCAT and QuikSCAT respond similarly to surface transitions. However, QuikSCAT measurements respond slightly stronger to the early melt of first-year ice, making it less sensitive to sea-ice dynamics. To retrieve the transitions, we employed an improved edge-detector algorithm, which was iterated and constrained using sea-ice concentration data, efficiently alleviating unreasonable outliers. This gives melt–freeze transitions over all Arctic sea ice north of 60°N at a 4.45 km resolution during 1999–2009 and 2009–2012 for QuikSCAT and ASCAT, respectively. Using the sensor overlap period, we show that the retrieved transitions retrieved from the different instruments are largely consistent across all regions in the Arctic sea-ice domain, indicating a robust consistency.
|
|
| 13. |
- Mortin, Jonas, et al.
(författare)
-
Melt onset over Arctic sea ice controlled by atmospheric moisture transport
- 2016
-
Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 43:12, s. 6636-6642
-
Tidskriftsartikel (refereegranskat)abstract
- The timing of melt onset affects the surface energy uptake throughout the melt season. Yet the processes triggering melt and causing its large interannual variability are not well understood. Here we show that melt onset over Arctic sea ice is initiated by positive anomalies of water vapor, clouds, and air temperatures that increase the downwelling longwave radiation (LWD) to the surface. The earlier melt onset occurs; the stronger are these anomalies. Downwelling shortwave radiation (SWD) is smaller than usual at melt onset, indicating that melt is not triggered by SWD. When melt occurs early, an anomalously opaque atmosphere with positive LWD anomalies preconditions the surface for weeks preceding melt. In contrast, when melt begins late, clearer than usual conditions are evident prior to melt. Hence, atmospheric processes are imperative for melt onset. It is also found that spring LWD increased during recent decades, consistent with trends toward an earlier melt onset.
|
|
| 14. |
- Mortin, Jonas, 1981-
(författare)
-
On the Arctic Seasonal Cycle
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The seasonal cycle of snow and sea ice is a fundamental feature of the Arctic climate system. In the Northern Hemisphere, about 55 million km2 of sea ice and snow undergo complete melt and freeze processes every year. Because snow and sea ice are much brighter (higher albedo) than the underlying surface, their presence reduces absorption of incoming solar energy at high latitudes. Therefore, changes of the sea-ice and snow cover have a large impact on the Arctic climate and possibly at lower latitudes. One of the most important determining factors of the seasonal snow and sea-ice cover is the timing of the seasonal melt-freeze transitions. Hence, in order to better understand Arctic climate variability, it is key to continuously monitor these transitions.This thesis presents an algorithm for obtaining melt-freeze transitions using scatterometers over both the land and sea-ice domains. These satellite-borne instruments emit radiation at microwave wavelengths and measure the returned signal. Several scatterometers are employed: QuikSCAT (1999–2009), ASCAT (2009–present), and OSCAT (2009–present). QuikSCAT and OSCAT operate at Ku-band (λ=2.2 cm) and ASCAT at C-band (λ=5.7 cm), resulting in slightly different surface interactions. This thesis discusses these dissimilarities over the Arctic sea-ice domain, and juxtaposes the time series of seasonal melt-freeze transitions from the three scatterometers and compares them with other, independent datasets.The interactions of snow and sea ice with other components of the Arctic climate system are complex. Models are commonly employed to disentangle these interactions. But this hinges upon robust and well-formulated models, reached by perpetual testing against observations. This thesis also presents an evaluation of how well eleven state-of-the-art global climate models reproduce the Arctic sea-ice cover and the summer length—given by the melt-freeze transitions—using surface observations of air temperature.
|
|
| 15. |
- Mortin, Jonas, 1981-, et al.
(författare)
-
OSCAT as a successor to QuikSCAT : a comparison over Arctic sea ice with emphasis on the seasonal melt-freeze transitions
-
Ingår i: Annals of Glaciology. - 0260-3055 .- 1727-5644.
-
Tidskriftsartikel (refereegranskat)abstract
- It is important to continuously monitor the seasonal melt-freeze transitions because of their influence on the Arctic climate system. The Ku-band scatterometer QuikSCAT was widely used to retrieve the seasonal transitions before its antenna failed in November 2009. In this study, we show that OSCAT, a Ku-band scatterometer launched in September 2009, can serve as a successor to QuikSCAT over Arctic sea ice. This is done by (1) comparing backscatter measurements acquired in overlapping time periods, and by (2) retrieving the seasonal melt-freeze transitions over Arctic sea ice from resolution-enhanced QuikSCAT and OSCAT data and comparing the results, also with other datasets. The main difference between the instruments, in terms of backscatter measurements, is the incidence angle in which backscatter is acquired, which yields backscatter discrepancies of 1-2 dB. This discrepancy is significantly smaller than the response of both sensors to surface melting and freezing processes. An edge-detection algorithm is employed that retrieves seasonal transitions from QuikSCAT (1999-2009) and OSCAT (2011-2013) at a 4.45-km spatial resolution. A comparison with transitions retrieved from the C-band scatterometer ASCAT (2009-2013) and from passive microwave radiometers (1999-2013) indicates that the transitions from scatterometers are largely consistent across all regions in the Arctic sea-ice domain.
|
|
