scholarly journals A New Look at the Summer Arctic Frontal Zone

2015 ◽  
Vol 28 (2) ◽  
pp. 737-754 ◽  
Author(s):  
Alex Crawford ◽  
Mark Serreze
Keyword(s):  
Arctic Ocean ◽  
Frontal Zone ◽  
Surface Wind ◽  
Past Research ◽  
Spatiotemporal Variability ◽  
The Arctic ◽  
Factors Affecting ◽  
Atmospheric Heating ◽  
Seasonal Characteristics ◽  
The Arctic Ocean

Abstract A notable characteristic of the summertime Arctic is the existence of a narrow band of strong horizontal temperature gradients spanning the coastlines of Siberia, Alaska, and western Canada that extends through a considerable depth of the troposphere. Past research has associated this summer Arctic Frontal Zone (AFZ) with contrasts in atmospheric heating between the Arctic Ocean and snow-free land, with its regional strength strongly influenced by topography; however, little is known about its variability. In this study, output from the latest generation of global atmospheric reanalyses is used to better constrain and define the summer AFZ, including its spatial and seasonal characteristics. The relative importance of different factors linked to its variability is then evaluated. The AFZ is best expressed in July and is manifested aloft as a separate Arctic jet feature at about 250 hPa. It is clearly associated with differential atmospheric heating, as evidenced by the sharp difference in surface energy balance terms between the Arctic Ocean and land. Furthermore, the AFZ is strongest over the coastline whether observed near the surface or throughout the troposphere. Interannual variations in peak strength of the AFZ are spatially heterogeneous and systematic near the surface (the 2-m level). Spatiotemporal variability is primarily dependent on factors affecting temperature over land, especially variability in cloud cover, surface wind direction, and the timing of the annual snow cover retreat. Local variability in the timing of annual sea ice retreat is also important through its control on temperatures over coastal seas.

scholarly journals Projected Changes in the Arctic Frontal Zone and Summer Arctic Cyclone Activity in the CESM Large Ensemble

2017 ◽  
Vol 30 (24) ◽  
pp. 9847-9869 ◽  
Author(s):  
Alex D. Crawford ◽  
Mark C. Serreze
Keyword(s):  
Arctic Ocean ◽  
Frontal Zone ◽  
Storm Track ◽  
Past Research ◽  
The Arctic ◽  
Cyclone Activity ◽  
Large Ensemble ◽  
The North ◽  
The Arctic Ocean ◽  
The Impact

The Arctic frontal zone (AFZ) is a narrow band of strong horizontal temperature gradients that develops along the Arctic Ocean coastline each summer in response to differential heating of the atmosphere over adjacent land and ocean surfaces. Past research has linked baroclinicity within the AFZ to summer Arctic cyclone development, especially by intensifying storms that migrate northward from the Eurasian continent. This study uses the Community Earth System Model Large Ensemble in conjunction with an advanced cyclone detection and tracking algorithm to assess how the AFZ, summer Arctic cyclone activity, and the relationship between them respond to warming under the representative concentration pathway 8.5 (RCP8.5) scenario. Under this strong warming scenario, the AFZ remains a significant cyclone intensifier. Changes to the AFZ are largely restricted to June, when earlier snowmelt leads to strengthening of land–ocean temperature contrasts. This strengthening is accompanied by enhanced cyclogenesis along the east Siberian coast, but no change is observed for overall cyclone frequency over the Arctic Ocean. However, simultaneous changes to subpolar storm tracks impact Arctic cyclone activity in all summer months, sometimes in opposition to the impact of the AFZ. In June, the storms migrating poleward to the Arctic Ocean become weaker under RCP8.5, leading to lower Arctic cyclone intensity. In July and August, the poleward shift of the North Pacific storm track enhances cyclone activity in the Beaufort and Chukchi Seas.

scholarly journals The Seasonal Variability of the Arctic Ocean Ekman Transport and Its Role in the Mixed Layer Heat and Salt Fluxes

2006 ◽  
Vol 19 (20) ◽  
pp. 5366-5387 ◽  
Author(s):  
Jiayan Yang
Keyword(s):  
Arctic Ocean ◽  
Mixed Layer ◽  
Seasonal Variability ◽  
Surface Wind ◽  
Beaufort Sea ◽  
Ekman Transport ◽  
The Arctic ◽  
Ekman Pumping ◽  
Basin Scale ◽  
The Arctic Ocean

Abstract The oceanic Ekman transport and pumping are among the most important parameters in studying the ocean general circulation and its variability. Upwelling due to the Ekman transport divergence has been identified as a leading mechanism for the seasonal to interannual variability of the upper-ocean heat content in many parts of the World Ocean, especially along coasts and the equator. Meanwhile, the Ekman pumping is the primary mechanism that drives basin-scale circulations in subtropical and subpolar oceans. In those ice-free oceans, the Ekman transport and pumping rate are calculated using the surface wind stress. In the ice-covered Arctic Ocean, the surface momentum flux comes from both air–water and ice–water stresses. The data required to compute these stresses are now available from satellite and buoy observations. But no basin-scale calculation of the Ekman transport in the Arctic Ocean has been done to date. In this study, a suite of satellite and buoy observations of ice motion, ice concentration, surface wind, etc., will be used to calculate the daily Ekman transport over the whole Arctic Ocean from 1978 to 2003 on a 25-km resolution. The seasonal variability and its relationship to the surface forcing fields will be examined. Meanwhile, the contribution of the Ekman transport to the seasonal fluxes of heat and salt to the Arctic Ocean mixed layer will be discussed. It was found that the greatest seasonal variations of Ekman transports of heat and salt occur in the southern Beaufort Sea in the fall and early winter when a strong anticyclonic wind and ice motion are present. The Ekman pumping velocity in the interior Beaufort Sea reaches as high as 10 cm day−1 in November while coastal upwelling is even stronger. The contributions of the Ekman transport to the heat and salt flux in the mixed layer are also considerable in the region.

scholarly journals Simulated Interannual Variations of Freshwater Content and Sea Surface Height in the Beaufort Sea*

2012 ◽  
Vol 25 (4) ◽  
pp. 1079-1095 ◽  
Author(s):  
Z. Long ◽  
W. Perrie ◽  
C. L. Tang ◽  
E. Dunlap ◽  
J. Wang
Keyword(s):  
Arctic Ocean ◽  
Surface Wind ◽  
Polar Vortex ◽  
Beaufort Sea ◽  
Sea Surface Height ◽  
Sea Surface ◽  
The Arctic ◽  
Rapid Decline ◽  
Interannual Variations ◽  
The Arctic Ocean

Abstract The authors investigate the interannual variations of freshwater content (FWC) and sea surface height (SSH) in the Beaufort Sea, particularly their increases during 2004–09, using a coupled ice–ocean model (CIOM), adapted for the Arctic Ocean to simulate the interannual variations. The CIOM simulation exhibits a (relative) salinity minimum in the Beaufort Sea and a warm Atlantic water layer in the Arctic Ocean, which is similar to the Polar Hydrographic Climatology (PHC), and captures the observed FWC maximum in the central Beaufort Sea, and the observed variation and rapid decline of total ice concentration, over the last 30 years. The model simulations of SSH and FWC suggest a significant increase in the central Beaufort Sea during 2004–09. The simulated SSH increase is about 8 cm, while the FWC increase is about 2.5 m, with most of these increases occurring in the center of the Beaufort gyre. The authors show that these increases are due to an increased surface wind stress curl during 2004–09, which increased the FWC in the Beaufort Sea by about 0.63 m yr−1 through Ekman pumping. Moreover, the increased surface wind is related to the interannual variation of the Arctic polar vortex at 500 hPa. During 2004–09, the polar vortex had significant weakness, which enhanced the Beaufort Sea high by affecting the frequency of synoptic weather systems in the region. In addition to the impacts of the polar vortex, enhanced melting of sea ice also contributes to the FWC increase by about 0.3 m yr−1 during 2004–09.

The shallowing surface temperature inversions in the Arctic

2021 ◽  
pp. 1-30
Author(s):  
Lin Zhang ◽  
Minghu Ding ◽  
Tingfeng Dou ◽  
Yi Huang ◽  
Junmei Lv ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
21St Century ◽  
Barents Sea ◽  
Atmospheric Stability ◽  
Heat Fluxes ◽  
Spatiotemporal Variability ◽  
The Arctic ◽  
The Arctic Ocean ◽  
Temperature Inversions

AbstractTemperature inversion plays an important role in various physical processes by affecting the atmospheric stability, regulating the development of clouds and fog, and controlling the transport of heat and moisture fluxes. In the past few decades, previous studies have analyzed the spatiotemporal variability of Arctic inversions, but few studies have investigated changes in temperature inversions. In this study, the changes in the depth of Arctic inversions in the mid-21st century are projected based on a 30-member ensemble from the Community Earth System Model Large Ensemble (CESM-LE) project. The ERA-Interim, JRA-55, and NCEP-NCAR reanalyses were employed to verify the model results. The CESM-LE can adequately reproduce the spatial distribution and trends of present-day inversion depth in the Arctic, and the simulation is better in winter. The mean inversion depth in the CESM-LE is slightly underestimated, and the discrepancy is less than 11 hPa within a reasonable range. The model results show that during the mid-21st century, the inversion depth will strongly decrease in autumn and slightly decrease in winter. The shallowing of inversion is most obvious over the Arctic Ocean, and the maximum decrease is over 65 hPa in the Pacific sector in autumn. In contrast, the largest decrease in the inversion depth, which is more than 45 hPa, occurs over the Barents Sea in winter. Moreover, the area where the inversion shallows is consistent with the area where the sea ice is retreating, indicating that the inversion depth over the Arctic Ocean in autumn and winter is likely regulated by the sea ice extent through modulating surface heat fluxes.

scholarly journals Does the Summer Arctic Frontal Zone Influence Arctic Ocean Cyclone Activity?

2016 ◽  
Vol 29 (13) ◽  
pp. 4977-4993 ◽  
Author(s):  
Alex D. Crawford ◽  
Mark C. Serreze
Keyword(s):  
Arctic Ocean ◽  
Large Scale ◽  
Frontal Zone ◽  
External Source ◽  
The Arctic ◽  
Cyclone Activity ◽  
Central Arctic Ocean ◽  
The Arctic Ocean ◽  
Summer Maximum ◽  
Horizontal Temperature Gradients

Abstract Extratropical cyclone activity over the central Arctic Ocean reaches its peak in summer. Previous research has argued for the existence of two external source regions for cyclones contributing to this summer maximum: the Eurasian continent interior and a narrow band of strong horizontal temperature gradients along the Arctic coastline known as the Arctic frontal zone (AFZ). This study incorporates data from an atmospheric reanalysis and an advanced cyclone detection and tracking algorithm to critically evaluate the relationship between the summer AFZ and cyclone activity in the central Arctic Ocean. Analysis of both individual cyclone tracks and seasonal fields of cyclone characteristics shows that the Arctic coast (and therefore the AFZ) is not a region of cyclogenesis. Rather, the AFZ acts as an intensification area for systems forming over Eurasia. As these systems migrate toward the Arctic Ocean, they experience greater deepening in situations when the AFZ is strong at midtropospheric levels. On a broader scale, intensity of the summer AFZ at midtropospheric levels has a positive correlation with cyclone intensity in the Arctic Ocean during summer, even when controlling for variability in the northern annular mode. Taken as a whole, these findings suggest that the summer AFZ can intensify cyclones that cross the coast into the Arctic Ocean, but focused modeling studies are needed to disentangle the relative importance of the AFZ, large-scale circulation patterns, and topographic controls.

scholarly journals Dark Warming

2016 ◽  
Vol 29 (2) ◽  
pp. 705-719 ◽  
Author(s):  
Melissa A. Burt ◽  
David A. Randall ◽  
Mark D. Branson
Keyword(s):  
Arctic Ocean ◽  
Air Temperature ◽  
Surface Wind ◽  
Surface Air Temperature ◽  
Longwave Radiation ◽  
Surface Wind Speed ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
The Arctic Ocean ◽  
Autumn And Winter

Abstract As the Arctic sea ice thins and ultimately disappears in a warming climate, its insulating power decreases. This causes the surface air temperature to approach the temperature of the relatively warm ocean water below the ice. The resulting increases in air temperature, water vapor, and cloudiness lead to an increase in the surface downwelling longwave radiation (DLR), which enables a further thinning of the ice. This positive ice–insulation feedback operates mainly in the autumn and winter. A climate change simulation with the Community Earth System Model shows that, averaged over the year, the increase in Arctic DLR is 3 times stronger than the increase in Arctic absorbed solar radiation at the surface. The warming of the surface air over the Arctic Ocean during fall and winter creates a strong thermal contrast with the colder surrounding continents. Sea level pressure falls over the Arctic Ocean, and the high-latitude circulation reorganizes into a shallow “winter monsoon.” The resulting increase in surface wind speed promotes stronger surface evaporation and higher humidity over portions of the Arctic Ocean, thus reinforcing the ice–insulation feedback.

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