scholarly journals Arctic Summer Airmass Transformation, Surface Inversions, and the Surface Energy Budget

2019 ◽  
Vol 32 (3) ◽  
pp. 769-789 ◽  
Author(s):  
Michael Tjernström ◽  
Matthew D. Shupe ◽  
Ian M. Brooks ◽  
Peggy Achtert ◽  
John Prytherch ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Energy ◽  
Sea Ice ◽  
Energy Budget ◽  
Longwave Radiation ◽  
Temperature Inversion ◽  
Surface Energy Budget ◽  
Surface Heating ◽  
The Arctic ◽  
Turbulent Heat

During the Arctic Clouds in Summer Experiment (ACSE) in summer 2014 a weeklong period of warm-air advection over melting sea ice, with the formation of a strong surface temperature inversion and dense fog, was observed. Based on an analysis of the surface energy budget, we formulated the hypothesis that, because of the airmass transformation, additional surface heating occurs during warm-air intrusions in a zone near the ice edge. To test this hypothesis, we explore all cases with surface inversions occurring during ACSE and then characterize the inversions in detail. We find that they always occur with advection from the south and are associated with subsidence. Analyzing only inversion cases over sea ice, we find two categories: one with increasing moisture in the inversion and one with constant or decreasing moisture with height. During surface inversions with increasing moisture with height, an extra 10–25 W m−2 of surface heating was observed, compared to cases without surface inversions; the surface turbulent heat flux was the largest single term. Cases with less moisture in the inversion were often cloud free and the extra solar radiation plus the turbulent surface heat flux caused by the inversion was roughly balanced by the loss of net longwave radiation.

scholarly journals Warm-Air Advection Over Melting Sea-Ice: A Lagrangian Case Study

2020 ◽  
Author(s):  
Cheng You ◽  
Michael Tjernström ◽  
Abhay Devasthale
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Longwave Radiation ◽  
Surface Energy Budget ◽  
The Arctic ◽  
Turbulent Heat ◽  
Initial Surface ◽  
Reanalysis Dataset ◽  
Surface Inversion ◽  
Strong Surface

AbstractObservations from the 2014 Arctic Clouds in Summer Experiment indicate that, in summer, warm-air advection over melting sea-ice results in a strong surface melting feedback forced by a very strong surface-based temperature inversion and fog formation exerting additional heat flux on the surface. Here, we analyze this case further using a combination of reanalysis dataset and satellite products in a Lagrangian framework, thereby extending the view spatially from the local icebreaker observations into a Langrangian perspective. The results confirm that warm-air advection induces a positive net surface-energy-budget anomaly, exerting positive longwave radiation and turbulent heat flux on the surface. Additionally, as warm and moist air penetrates farther into the Arctic, cloud-top cooling and surface mixing eventually erode the surface inversion downstream. The initial surface inversion splits into two elevated inversions while the air columns below the elevated inversions transform into well-mixed layers.

scholarly journals Mechanism of Seasonal Arctic Sea Ice Evolution and Arctic Amplification

2016 ◽  
Author(s):  
Kwang-Yul Kim ◽  
Benjamin D. Hamlington ◽  
Hanna Na ◽  
Jinju Kim
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
Longwave Radiation ◽  
The Arctic ◽  
Turbulent Heat ◽  
Arctic Amplification ◽  
Ice Melting ◽  
Downward Longwave Radiation

Abstract. Sea ice melting is proposed as a primary reason for the Artic amplification, although physical mechanism of the Arctic amplification and its connection with sea ice melting is still in debate. In the present study, monthly ERA-interim reanalysis data are analyzed via cyclostationary empirical orthogonal function analysis to understand the seasonal mechanism of sea ice melting in the Arctic Ocean and the Arctic amplification. While sea ice melting is widespread over much of the perimeter of the Arctic Ocean in summer, sea ice remains to be thin in winter only in the Barents-Kara Seas. Excessive turbulent heat flux through the sea surface exposed to air due to sea ice melting warms the atmospheric column. Warmer air increases the downward longwave radiation and subsequently surface air temperature, which facilitates sea surface remains to be ice free. A 1 % reduction in sea ice concentration in winter leads to ~ 0.76 W m−2 increase in upward heat flux, ~ 0.07 K increase in 850 hPa air temperature, ~ 0.97 W m−2 increase in downward longwave radiation, and ~ 0.26 K increase in surface air temperature. This positive feedback mechanism is not clearly observed in the Laptev, East Siberian, Chukchi, and Beaufort Seas, since sea ice refreezes in late fall (November) before excessive turbulent heat flux is available for warming the atmospheric column in winter. A detailed seasonal heat budget is presented in order to understand specific differences between the Barents-Kara Seas and Laptev, East Siberian, Chukchi, and Beaufort Seas.

scholarly journals Surface energy budget of landfast sea ice during the transitions from winter to snowmelt and melt pond onset: The importance of net longwave radiation and cyclone forcings

2014 ◽  
Vol 119 (6) ◽  
pp. 3679-3693 ◽  
Author(s):  
B. G. T. Else ◽  
T. N. Papakyriakou ◽  
R. Raddatz ◽  
R. J. Galley ◽  
C. J. Mundy ◽  
...  
Keyword(s):  
Surface Energy ◽  
Sea Ice ◽  
Energy Budget ◽  
Longwave Radiation ◽  
Surface Energy Budget ◽  
Melt Pond ◽  
Landfast Sea Ice

scholarly journals Projected Changes in Soil Temperature and Surface Energy Budget Components over the Alps and Northern Italy

Water ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 954 ◽  
Author(s):  
Claudio Cassardo ◽  
Seon Park ◽  
Sungmin O ◽  
Marco Galli
Keyword(s):  
Heat Flux ◽  
Surface Energy ◽  
Soil Temperature ◽  
Energy Budget ◽  
Regional Climate ◽  
Northern Italy ◽  
Surface Energy Budget ◽  
Future Climate ◽  
Radiative Properties ◽  
The Alps

This study investigates the potential changes in surface energy budget components under certain future climate conditions over the Alps and Northern Italy. The regional climate scenarios are obtained though the Regional Climate Model version 3 (RegCM3) runs, based on a reference climate (1961–1990) and the future climate (2071–2100) via the A2 and B2 scenarios. The energy budget components are calculated by employing the University of Torino model of land Processes Interaction with Atmosphere (UTOPIA), and using the RegCM3 outputs as input data. Our results depict a significant change in the energy budget components during springtime over high-mountain areas, whereas the most relevant difference over the plain areas is the increase in latent heat flux and hence, evapotranspiration during summertime. The precedence of snow-melting season over the Alps is evidenced by the earlier increase in sensible heat flux. The annual mean number of warm and cold days is evaluated by analyzing the top-layer soil temperature and shows a large increment (slight reduction) of warm (cold) days. These changes at the end of this century could influence the regional radiative properties and energy cycles and thus, exert significant impacts on human life and general infrastructures.

scholarly journals Downslope föhn winds over the Antarctic Peninsula and their effect on the Larsen ice shelves

2014 ◽  
Vol 14 (18) ◽  
pp. 9481-9509 ◽  
Author(s):  
D. P. Grosvenor ◽  
J. C. King ◽  
T. W. Choularton ◽  
T. Lachlan-Cope
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Surface Energy ◽  
Antarctic Peninsula ◽  
Energy Budget ◽  
Surface Flux ◽  
Surface Energy Budget ◽  
Ice Shelf ◽  
Aircraft Observations ◽  
The Antarctic

Abstract. Mesoscale model simulations are presented of a westerly föhn event over the Antarctic Peninsula mountain ridge and onto the Larsen C ice shelf, just south of the recently collapsed Larsen B ice shelf. Aircraft observations showed the presence of föhn jets descending near the ice shelf surface with maximum wind speeds at 250–350 m in height. Surface flux measurements suggested that melting was occurring. Simulated profiles of wind speed, temperature and wind direction were very similar to the observations. However, the good match only occurred at a model time corresponding to ~9 h before the aircraft observations were made since the model föhn jets died down after this. This was despite the fact that the model was nudged towards analysis for heights greater than ~1.15 km above the surface. Timing issues aside, the otherwise good comparison between the model and observations gave confidence that the model flow structure was similar to that in reality. Details of the model jet structure are explored and discussed and are found to have ramifications for the placement of automatic weather station (AWS) stations on the ice shelf in order to detect föhn flow. Cross sections of the flow are also examined and were found to compare well to the aircraft measurements. Gravity wave breaking above the mountain crest likely created a~situation similar to hydraulic flow and allowed föhn flow and ice shelf surface warming to occur despite strong upwind blocking, which in previous studies of this region has generally not been considered. Our results therefore suggest that reduced upwind blocking, due to wind speed increases or stability decreases, might not result in an increased likelihood of föhn events over the Antarctic Peninsula, as previously suggested. The surface energy budget of the model during the melting periods showed that the net downwelling short-wave surface flux was the largest contributor to the melting energy, indicating that the cloud clearing effect of föhn events is likely to be the most important factor for increased melting relative to non-föhn days. The results also indicate that the warmth of the föhn jets through sensible heat flux ("SH") may not be critical in causing melting beyond boundary layer stabilisation effects (which may help to prevent cloud cover and suppress loss of heat by convection) and are actually cancelled by latent heat flux ("LH") effects (snow ablation). It was found that ground heat flux ("GRD") was likely to be an important factor when considering the changing surface energy budget for the southern regions of the ice shelf as the climate warms.

scholarly journals Atmospheric components of the surface energy budget over young sea ice: Results from the N-ICE2015 campaign

2017 ◽  
Vol 122 (16) ◽  
pp. 8427-8446 ◽  
Author(s):  
Von P. Walden ◽  
Stephen R. Hudson ◽  
Lana Cohen ◽  
Sarah Y. Murphy ◽  
Mats A. Granskog
Keyword(s):  
Surface Energy ◽  
Sea Ice ◽  
Energy Budget ◽  
Surface Energy Budget

scholarly journals On the surface energy budget of sea ice

1997 ◽  
Vol 43 (143) ◽  
pp. 122-130 ◽  
Author(s):  
Gerd Wendler ◽  
Ute Adolphs ◽  
Adrian Hauser ◽  
Blake Moore
Keyword(s):  
Surface Energy ◽  
Sea Ice ◽  
Energy Budget ◽  
High Surface ◽  
Open Water ◽  
Ice Cover ◽  
Surface Energy Budget ◽  
Net Radiation ◽  
Pack Ice ◽  
Ice Concentration

AbstractThe surface energy budget was investigated during a cruise through the pack ice in the Southern Ocean. The time of observation was close to mid-summer. Some of the more important findings were: The mean albedo varied from 11 % for open water to 59% for 10/10 ice cover. Hourly values span the range from 6% (open water) to 76% (total ice cover).The net heat flux into the ocean (B) was on average 109 W m−2, If this energy were used solely for melting of sea ice, 30 mm could be melted each day.For low surface albedos (ice concentration below 7/10), the net radiation increased with decreasing cloudiness. However, the opposite was the case for a high surface albedo. The last point shows the importance of clouds on the surface energy budget. Not only should their presence or absence be known but also the reflectivity of the underlying surface, as it might change the net radiation in opposite ways.

scholarly journals Measurements of turbulence transfer in the near-surface layer over the Antarctic sea-ice surface from April through November in 2016

2020 ◽  
Vol 61 (82) ◽  
pp. 12-23
Author(s):  
Changwei Liu ◽  
Zhiqiu Gao ◽  
Qinghua Yang ◽  
Bo Han ◽  
Hong Wang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Roughness Length ◽  
Sensible Heat Flux ◽  
Surface Energy Budget ◽  
The Arctic ◽  
Conductive Heat ◽  
Near Surface ◽  
Antarctic Sea Ice ◽  
The Antarctic

AbstractThe surface energy budget over the Antarctic sea ice from 8 April 2016 through 26 November 2016 are presented. From April to October, Sensible heat flux (SH) and subsurface conductive heat flux (G) were the heat source of surface while latent heat flux (LE) and net radiation flux (Rn) were the heat sink of surface. Our results showed larger downward SH (due to the warmer air in our site) and upward LE (due to the drier air and higher wind speed in our site) compared with SHEBA data. However, the values of SH in N-ICE2015 campaign, which located at a zone with stronger winds and more advection of heat in the Arctic, were comparable to our results under clear skies. The values of aerodynamic roughness length (z0m) and scalar roughness length for temperature (z0h), being 1.9 × 10−3 m and 3.7 × 10−5 m, were suggested in this study. It is found that snow melting might increase z0m. Our results also indicate that the value of log(z0h/z0m) was related to the stability of stratification. In addition, several representative parameterization schemes for z0h have been tested and a couple of schemes were found to make a better performance.

scholarly journals Sensitivity of Northern Hemisphere climate to ice–ocean interface heat flux parameterizations

2021 ◽  
Vol 14 (8) ◽  
pp. 4891-4908
Author(s):  
Xiaoxu Shi ◽  
Dirk Notz ◽  
Jiping Liu ◽  
Hu Yang ◽  
Gerrit Lohmann
Keyword(s):  
Heat Flux ◽  
Heat Exchange ◽  
Sea Ice ◽  
Temperature Difference ◽  
Climate Model ◽  
Turbulent Heat Flux ◽  
The Arctic ◽  
Ice Thickness ◽  
Turbulent Heat ◽  
Sea Ice Thickness

Abstract. We investigate the impact of three different parameterizations of ice–ocean heat exchange on modeled sea ice thickness, sea ice concentration, and water masses. These three parameterizations are (1) an ice bath assumption with the ocean temperature fixed at the freezing temperature; (2) a two-equation turbulent heat flux parameterization with ice–ocean heat exchange depending linearly on the temperature difference between the underlying ocean and the ice–ocean interface, whose temperature is kept at the freezing point of the seawater; and (3) a three-equation turbulent heat flux approach in which the ice–ocean heat flux depends on the temperature difference between the underlying ocean and the ice–ocean interface, whose temperature is calculated based on the local salinity set by the ice ablation rate. Based on model simulations with the stand-alone sea ice model CICE, the ice–ocean model MPIOM, and the climate model COSMOS, we find that compared to the most complex parameterization (3), the approaches (1) and (2) result in thinner Arctic sea ice, cooler water beneath high-concentration ice and warmer water towards the ice edge, and a lower salinity in the Arctic Ocean mixed layer. In particular, parameterization (1) results in the smallest sea ice thickness among the three parameterizations, as in this parameterization all potential heat in the underlying ocean is used for the melting of the sea ice above. For the same reason, the upper ocean layer of the central Arctic is cooler when using parameterization (1) compared to (2) and (3). Finally, in the fully coupled climate model COSMOS, parameterizations (1) and (2) result in a fairly similar oceanic or atmospheric circulation. In contrast, the most realistic parameterization (3) leads to an enhanced Atlantic meridional overturning circulation (AMOC), a more positive North Atlantic Oscillation (NAO) mode and a weakened Aleutian Low.

scholarly journals Understanding the Mechanism of Arctic Amplification and Sea Ice Loss

2017 ◽  
Author(s):  
Kwang-Yul Kim ◽  
Jinju Kim ◽  
Saerim Yeo ◽  
Hanna Na ◽  
Benjamin D. Hamlington ◽  
...  
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Longwave Radiation ◽  
Reanalysis Data ◽  
Specific Humidity ◽  
Turbulent Heat ◽  
Feedback Process ◽  
Downward Longwave Radiation ◽  
Barents And Kara Seas ◽  
Sea Ice Reduction

Abstract. Sea ice reduction is accelerating in the Barents and Kara Seas. Several mechanisms are proposed to explain the accelerated loss of polar sea ice, which remains an open question. In the present study, the detailed physical mechanism of sea ice reduction in winter is identified using the daily ERA interim reanalysis data. Downward longwave radiation is an essential element for sea ice reduction, but can only be sustained by excessive upward heat flux from the sea surface exposed to air in the region of sea ice loss. The increased turbulent heat flux is used to increase air temperature and specific humidity in the lower troposphere, which in turn increases downward longwave radiation. This feedback process is clearly observed in the Barents and Kara Seas in the reanalysis data. A quantitative assessment reveals that this feedback process is amplifying at the rate of ~ 8.9 % every year during 1979–2016. Based on this estimate, sea ice will completely disappear in the Barents and Kara Seas by around 2025. Availability of excessive heat flux is necessary for the maintenance of this feedback process; a similar mechanism of sea ice loss is expected to take place over the sea-ice covered polar region when sea ice is not fully recovered in winter.

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