The importance of capturing late melt season sea ice conditions for modeling the western Arctic ocean boundary layer

To better understand the response of the western Arctic upper ocean to late summer ice-ocean interactions, a range of surface, interior, and basal sea ice conditions were simulated in a 1-D turbulent boundary layer model. In-ice and under-ice autonomous observations from the 2014 Marginal Ice Zone Experiment provided a complete characterization of the late melt-season sea ice and were used to set initial conditions, update boundary conditions, and conduct model validation studies. Results show that underestimates of open water and melt pond fraction at the sea ice surface had the largest influence on ocean-to-ice turbulent heat fluxes reducing basal melt rates by as much as 32%. This substantial reduction in latent heat loss was attributed to underestimates of open water areas and the exclusion of melt ponds by low-resolution synthetic aperture radar imagery. However, the greatest overall effect on the ice-ocean boundary layer came from mischaracterizations of basal roughness, with smooth ice scenarios resulting in 7 m of summer halocline shoaling and preservation of the near-surface temperature maximum. Rough ice conditions showed a 23% deepening of the mixed layer and erosion of heat storage above 40 m. Adjustments of conductive heat fluxes had little effect on the near-interface heat budget due to small internal thermal gradients within the late summer sea ice. Results from the 1-D boundary layer simulations highlight the most influential components of sea ice structure during late summer conditions and provide the magnitude of errors expected when ice conditions are mischaracterized.

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The Boundary Layer Response to Recent Arctic Sea Ice Loss and Implications for High-Latitude Climate Feedbacks

Journal of Climate ◽

10.1175/2010jcli3651.1 ◽

2011 ◽

Vol 24 (2) ◽

pp. 428-447 ◽

Cited By ~ 47

Author(s):

J. E. Kay ◽

K. Raeder ◽

A. Gettelman ◽

J. Anderson

Keyword(s):

Boundary Layer ◽

Sea Ice ◽

Mixed Boundary ◽

Open Water ◽

Arctic Sea Ice ◽

Energy Budgets ◽

Climate Feedbacks ◽

Near Surface ◽

Stratus Clouds ◽

Arctic Sea Ice Loss

Abstract This study documents and evaluates the boundary layer and energy budget response to record low 2007 sea ice extents in the Community Atmosphere Model version 4 (CAM4) using 1-day observationally constrained forecasts and 10-yr runs with a freely evolving atmosphere. While near-surface temperature and humidity are minimally affected by sea ice loss in July 2007 forecasts, near-surface stability decreases and atmospheric humidity increases aloft over newly open water in September 2007 forecasts. Ubiquitous low cloud increases over the newly ice-free Arctic Ocean are found in both the July 2007 and the September 2007 forecasts. In response to the 2007 sea ice loss, net surface [top of the atmosphere (TOA)] energy budgets change by +19.4 W m−2 (+21.0 W m−2) and −17.9 W m−2 (+1.4 W m−2) in the July 2007 and September 2007 forecasts, respectively. While many aspects of the forecasted response to sea ice loss are consistent with physical expectations and available observations, CAM4’s ubiquitous July 2007 cloud increases over newly open water are not. The unrealistic cloud response results from the global application of parameterization designed to diagnose stratus clouds based on lower-tropospheric stability (CLDST). In the Arctic, the well-mixed boundary layer assumption implicit in CLDST is violated. Requiring a well-mixed boundary layer to diagnose stratus clouds improves the CAM4 cloud response to sea ice loss and increases July 2007 surface (TOA) energy budgets over newly open water by +11 W m−2 (+14.9 W m−2). Of importance to high-latitude climate feedbacks, unrealistic stratus cloud compensation for sea ice loss occurs only when stable and dry atmospheric conditions exist. Therefore, coupled climate projections that use CAM4 will underpredict Arctic sea ice loss only when dry and stable summer conditions occur.

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Modelling inter-annual sea-ice variability off eastern Canada

Annals of Glaciology ◽

10.3189/s0260305500014221 ◽

1997 ◽

Vol 25 ◽

pp. 322-326

Author(s):

J. R. Makko ◽

D. B. Fissel ◽

D. Haller

Keyword(s):

Sea Ice ◽

Heat Fluxes ◽

Box Model ◽

Surface Currents ◽

Eastern Canada ◽

Near Surface ◽

Surface Temperatures ◽

External Model ◽

Good Reproduction ◽

Ice Conditions

Inter-annual sea-ice variability north of 55°N in eastern Canada was explored with a box model incorporating annually invariant, bathymetrically dependent ocean heat fluxes and near-surface currents. Using inputs of ice concentrations, regional surface temperatures and geostrophic winds at external model boundaries, ice composition was simulated in seven thickness categories at 10 day intervals during three annual ice seasons. Comparisons indicated good reproduction of observed inter-annual differences in regional ice volumes during critical January-March periods. Additional simulations of artificial cutoffs in southward ice fluxes showed that advective influence decreases with latitude and dominates the development of spring ice conditions in areas south of 60°N.

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Radiometrie measurements of sea-ice surface temperature in East Antarctica

Annals of Glaciology ◽

10.3189/1998aog27-1-466-470 ◽

1998 ◽

Vol 27 ◽

pp. 466-470

Author(s):

Kelvin J. Michael ◽

Clemente S. Hungria ◽

R. A. Massom

Keyword(s):

Sea Ice ◽

Surface Temperature ◽

Snow Cover ◽

Open Water ◽

Thermal Infrared ◽

Near Surface ◽

Video Footage ◽

Antarctic Sea Ice ◽

Ice Surface ◽

Ice Conditions

This paper presents surface temperature data collected over East Antarctic sea ice by two thermal infrared radiometers mounted on the RSV Aurora Australis in March-May 1993. Operating at wavelengths equivalent to those utilised by channels 4 and 5 of AVHRR and similar channels of ATSR, the radiometers provided high-reso-lution data on surface (skin) temperature along the ship track. Additional information on the sea-ice conditions was obtained from hourly observations made from The ship's bridge, video footage and direct measurements made at ice stations. Following calibration, time series of temperatures from each of the radiometers were compared wi th ice-surface and near-surface air temperatures. Observed changes in the surface temperature are related to different snow and ice conditions. For a given air temperature, the surface temperature depends upon the thickness of ice and its snow cover. While open water areas (leads) have temperatures near -2.0°C, thick ice is characterised by surface temperatures which approximate those of the air. Taken as a whole, the along-track profile of surface temperature provides a proxy estimate of The proportion of open water and thin ice with in the pack. The presence of a snow cover has a significant effect on the surface temperature. It is anticipated that the results will be of use in the validation of sea-ice models and satellite thermal infrared data.

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Field observations and results of a 1-D boundary layer model for developing near-surface temperature maxima in the Western Arctic

Elem Sci Anth ◽

10.1525/elementa.195 ◽

2017 ◽

Vol 5 ◽

Cited By ~ 1

Author(s):

Shawn G. Gallaher ◽

Timothy P. Stanton ◽

William J. Shaw ◽

Sung-Ho Kang ◽

Joo-Hong Kim ◽

...

Keyword(s):

Boundary Layer ◽

Solar Radiation ◽

Late Summer ◽

Early Summer ◽

Summer Season ◽

Layer Model ◽

Near Surface ◽

Boundary Layer Model ◽

Western Arctic ◽

Wind Events

Summer sea ice extent in the Western Arctic has decreased significantly in recent years resulting in increased solar input into the upper ocean. Here, a comprehensive set of in situshipboard, on-ice, and autonomous ice-ocean measurements were made of the early stages of formation of the near-surface temperature maximum (NSTM) in the Canada Basin. These observations along with the results from a 1-D turbulent boundary layer model indicate that heat storage associated with NSTM formation is largely due to the absorption of penetrating solar radiation just below a protective summer halocline. The depth of the summer halocline was found to be the most important factor for determining the amount of solar radiation absorbed in the NSTM layer, while halocline strength controlled the amount of heat removed from the NSTM by turbulent transport. Observations using the Naval Postgraduate School Turbulence Frame show that the NSTM was able to persist despite periods of intermittent turbulence because transport rates were too small to remove significant amounts of heat from the NSTM layer. The development of the early and late summer halocline and NSTM were found to be linked to summer season buoyancy and wind events. For the early summer NSTM, 1-D boundary layer model results show that melt pond drainage provides sufficient buoyancy to the summer halocline to prevent subsequent wind events from mixing out the NSTM. For the late summer NSTM,limited freshwater inputs reduce the strength of the summer halocline making the balance between interfacial stresses and buoyancy more tenuous. As a result, the late summer NSTM is an ephemeral feature dependent on local wind conditions, while the early summer NSTM is more persistent and able to store heat in the near-surface ocean beyond the summer season.

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Modelling inter-annual sea-ice variability off eastern Canada

Annals of Glaciology ◽

10.1017/s0260305500014221 ◽

1997 ◽

Vol 25 ◽

pp. 322-326

Author(s):

J. R. Makko ◽

D. B. Fissel ◽

D. Haller

Keyword(s):

Sea Ice ◽

Heat Fluxes ◽

Box Model ◽

Surface Currents ◽

Eastern Canada ◽

Near Surface ◽

Surface Temperatures ◽

External Model ◽

Good Reproduction ◽

Ice Conditions

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Airborne observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-8147-2015 ◽

2015 ◽

Vol 15 (14) ◽

pp. 8147-8163 ◽

Cited By ~ 12

Author(s):

M. Schäfer ◽

E. Bierwirth ◽

A. Ehrlich ◽

E. Jäkel ◽

M. Wendisch

Keyword(s):

Boundary Layer ◽

Radiative Transfer ◽

Sea Ice ◽

Three Dimensional ◽

Open Water ◽

Radiative Effects ◽

Arctic Boundary Layer ◽

Boundary Layer Clouds ◽

Ice Edge ◽

Ice Floes

Abstract. Based on airborne spectral imaging observations, three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces were identified and quantified. A method is presented to discriminate between sea ice and open water under cloudy conditions based on airborne nadir reflectivity γλ measurements in the visible spectral range. In cloudy cases the transition of γλ from open water to sea ice is not instantaneous but horizontally smoothed. In general, clouds reduce γλ above bright surfaces in the vicinity of open water, while γλ above open sea is enhanced. With the help of observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge (for a dark-ocean albedo of αwater = 0.042 and a sea-ice albedo of αice = 0.91 at 645 nm wavelength). The affected distance Δ L was found to depend on both cloud and sea ice properties. For a low-level cloud at 0–200 m altitude, as observed during the Arctic field campaign VERtical Distribution of Ice in Arctic clouds (VERDI) in 2012, an increase in the cloud optical thickness τ from 1 to 10 leads to a decrease in Δ L from 600 to 250 m. An increase in the cloud base altitude or cloud geometrical thickness results in an increase in Δ L; for τ = 1/10 Δ L = 2200 m/1250 m in case of a cloud at 500–1000 m altitude. To quantify the effect for different shapes and sizes of ice floes, radiative transfer simulations were performed with various albedo fields (infinitely long straight ice edge, circular ice floes, squares, realistic ice floe field). The simulations show that Δ L increases with increasing radius of the ice floe and reaches maximum values for ice floes with radii larger than 6 km (500–1000 m cloud altitude), which matches the results found for an infinitely long, straight ice edge. Furthermore, the influence of these 3-D radiative effects on the retrieved cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 and 30 % in retrievals of τ and effective radius reff, respectively. With the help of Δ L, an estimate of the distance to the ice edge is given, where the retrieval uncertainties due to 3-D radiative effects are negligible.

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The role of open lead interactions in atmospheric ozone variability between Arctic coastal and inland sites

Elem Sci Anth ◽

10.12952/journal.elementa.000109 ◽

2016 ◽

Vol 4 ◽

Cited By ~ 2

Author(s):

Peter K. Peterson ◽

Kerri A. Pratt ◽

William R. Simpson ◽

Son V. Nghiem ◽

Lemuel X. Pérez Pérez ◽

...

Keyword(s):

Boundary Layer ◽

Sea Ice ◽

Ozone Depletion ◽

Surface Ozone ◽

Optical Absorption Spectroscopy ◽

Atmospheric Ozone ◽

Vertical Profiles ◽

Large Spatial Scale ◽

Near Surface ◽

Air Masses

Abstract Boundary layer atmospheric ozone depletion events (ODEs) are commonly observed across polar sea ice regions following polar sunrise. During March-April 2005 in Alaska, the coastal site of Barrow and inland site of Atqasuk experienced ODEs (O3< 10 nmol mol-1) concurrently for 31% of the observations, consistent with large spatial scale ozone depletion. However, 7% of the time ODEs were exclusively observed inland at Atqasuk. This phenomenon also occurred during one of nine flights during the BRomine, Ozone, and Mercury EXperiment (BROMEX), when atmospheric vertical profiles at both sites showed near-surface ozone depletion only at Atqasuk on 28 March 2012. Concurrent in-flight BrO measurements made using nadir scanning differential optical absorption spectroscopy (DOAS) showed the differences in ozone vertical profiles at these two sites could not be attributed to differences in locally occurring halogen chemistry. During both studies, backward air mass trajectories showed that the Barrow air masses observed had interacted with open sea ice leads, causing increased vertical mixing and recovery of ozone at Barrow and not Atqasuk, where the air masses only interacted with tundra and consolidated sea ice. These observations suggest that, while it is typical for coastal and inland sites to have similar ozone conditions, open leads may cause heterogeneity in the chemical composition of the springtime Arctic boundary layer over coastal and inland areas adjacent to sea ice regions.

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Evaluation of regional NWP results for sea ice covered Bothnia Bay (Baltic Sea) in winter 2020.

10.5194/egusphere-egu21-14612 ◽

2021 ◽

Author(s):

Marta Wenta ◽

Agnieszka Herman

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Sea Ice ◽

Surface Temperature ◽

Atmospheric Boundary Layer ◽

Baltic Sea ◽

Polar Regions ◽

Near Surface ◽

Accurate Representation ◽

Complex Processes

The ongoing development of NWP (Numerical Weather Prediction) models and their increasing horizontal resolution have significantly improved forecasting capabilities. However, in the polar regions models struggle with the representation of near-surface atmospheric properties and the vertical structure of the atmospheric boundary layer (ABL) over sea ice. Particularly difficult to resolve are near-surface temperature, wind speed, and humidity, along with diurnal changes of those properties. Many of the complex processes happening at the interface of sea ice and atmosphere, i.e. vertical fluxes, turbulence, atmosphere - surface coupling are poorly parameterized or not represented in the models at all. Limited data coverage and our poor understanding of the complex processes taking place in the polar ABL limit the development of suitable parametrizations. We try to contribute to the ongoing effort to improve the forecast skill in polar regions through the analysis of unmanned aerial vehicles (UAVs) and automatic weather station (AWS) atmospheric measurements from the coastal area of Bothnia Bay (Wenta et. al., 2021), and the application of those datasets for the analysis of regional NWP models' forecasts.&#160;Data collected during HAOS (Hailuoto Atmospheric Observations over Sea ice) campaign (Wenta et. al., 2021) is used for the evaluation of regional NWP models results from AROME (Applications of Research to Operations at Mesoscale) - Arctic, HIRLAM (High Resolution Limited Area Model) and WRF (Weather Research and Forecasting). The presented analysis focuses on 27 Feb. 2020 - 2 Mar. 2020, the time of the HAOS campaign, shortly after the formation of new, thin sea ice off the westernmost point of Hailuoto island.&#160; Throughout the studied period weather conditions changed from very cold (-14&#8451;), dry and cloud-free to warmer (~ -5&#8451;), more humid and opaquely cloudy. We evaluate models&#8217; ability to correctly resolve near-surface temperature, humidity, and wind speed, along with vertical changes of temperature and humidity over the sea ice. It is found that generally, models struggle with an accurate representation of surface-based temperature inversions, vertical variations of humidity, and temporal wind speed changes. Furthermore, a WRF Single Columng Model (SCM) is launched to study whether specific WRF planetary boundary layer parameterizations (MYJ, YSU, MYNN, QNSE), vertical resolution, and more accurate representation of surface conditions increase the WRF model&#8217;s ability to resolve the ABL above sea ice in the Bay of Bothnia. Experiments with WRF SCM are also used to determine the possible reasons behind model&#8217;s biases. Preliminary results show that accurate representation of sea ice conditions, including thickness, surface temperature, albedo, and snow coverage is crucial for increasing the quality of NWP models forecasts. We emphasize the importance of further development of parametrizations focusing on the processes at the sea ice-atmosphere interface.&#160;Reference:Wenta, M., Brus, D., Doulgeris, K., Vakkari, V., and Herman, A.: Winter atmospheric boundary layer observations over sea ice in the coastal zone of the Bay of Bothnia (Baltic Sea), Earth Syst. Sci. Data, 13, 33&#8211;42, https://doi.org/10.5194/essd-13-33-2021, 2021.&#160;

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A parameter model of gas exchange for the seasonal sea ice zone

Ocean Science ◽

10.5194/os-10-17-2014 ◽

2014 ◽

Vol 10 (1) ◽

pp. 17-28 ◽

Cited By ~ 37

Author(s):

B. Loose ◽

W. R. McGillis ◽

D. Perovich ◽

C. J. Zappa ◽

P. Schlosser

Keyword(s):

Boundary Layer ◽

Gas Exchange ◽

Sea Ice ◽

Open Water ◽

Field Studies ◽

The Arctic ◽

Gas Transfer ◽

Transfer Velocity ◽

Using Data ◽

Effective Transfer

Abstract. Carbon budgets for the polar oceans require better constraint on air–sea gas exchange in the sea ice zone (SIZ). Here, we utilize advances in the theory of turbulence, mixing and air–sea flux in the ice–ocean boundary layer (IOBL) to formulate a simple model for gas exchange when the surface ocean is partially covered by sea ice. The gas transfer velocity (k) is related to shear-driven and convection-driven turbulence in the aqueous mass boundary layer, and to the mean-squared wave slope at the air–sea interface. We use the model to estimate k along the drift track of ice-tethered profilers (ITPs) in the Arctic. Individual estimates of daily-averaged k from ITP drifts ranged between 1.1 and 22 m d−1, and the fraction of open water (f) ranged from 0 to 0.83. Converted to area-weighted effective transfer velocities (keff), the minimum value of keff was 10−55 m d−1 near f = 0 with values exceeding keff = 5 m d−1 at f = 0.4. The model indicates that effects from shear and convection in the sea ice zone contribute an additional 40% to the magnitude of keff, beyond what would be predicted from an estimate of keff based solely upon a wind speed parameterization. Although the ultimate scaling relationship for gas exchange in the sea ice zone will require validation in laboratory and field studies, the basic parameter model described here demonstrates that it is feasible to formulate estimates of k based upon properties of the IOBL using data sources that presently exist.

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Enhanced tropospheric BrO over Antarctic sea ice in mid winter observed by MAX-DOAS on board the research vessel Polarstern

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-3129-2007 ◽

2007 ◽

Vol 7 (12) ◽

pp. 3129-3142 ◽

Cited By ~ 63

Author(s):

T. Wagner ◽

O. Ibrahim ◽

R. Sinreich ◽

U. Frieß ◽

R. von Glasow ◽

...

Keyword(s):

Boundary Layer ◽

Sea Ice ◽

Vertical Mixing ◽

Satellite Observations ◽

Research Vessel ◽

Optical Absorption Spectroscopy ◽

Back Trajectory ◽

First Year ◽

Polar Regions ◽

Near Surface

Abstract. We present Multi AXis-Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of tropospheric BrO carried out on board the German research vessel Polarstern during the Antarctic winter 2006. Polarstern entered the area of first year sea ice around Antarctica on 24 June 2006 and stayed within this area until 15 August 2006. For the period when the ship cruised inside the first year sea ice belt, enhanced BrO concentrations were almost continuously observed. Outside the first year sea ice belt, typically low BrO concentrations were found. Based on back trajectory calculations we find a positive correlation between the observed BrO differential slant column densities (ΔSCDs) and the duration for which the air masses had been in contact with the sea ice surface prior to the measurement. While we can not completely rule out that in several cases the highest BrO concentrations might be located close to the ground, our observations indicate that the maximum BrO concentrations might typically exist in a (possibly extended) layer around the upper edge of the boundary layer. Besides the effect of a decreasing pH of sea salt aerosol with altitude and therefore an increase of BrO with height, this finding might be also related to vertical mixing of air from the free troposphere with the boundary layer, probably caused by convection over the warm ocean surface at polynyas and cracks in the ice. Strong vertical gradients of BrO and O3 could also explain why we found enhanced BrO levels almost continuously for the observations within the sea ice. Based on our estimated BrO profiles we derive BrO mixing ratios of several ten ppt, which is slightly higher than many existing observations. Our observations indicate that enhanced BrO concentrations around Antarctica exist about one month earlier than observed by satellite instruments. From detailed radiative transfer simulations we find that MAX-DOAS observations are up to about one order of magnitude more sensitive to near-surface BrO than satellite observations. In contrast to satellite observations the MAX-DOAS sensitivity hardly decreases for large solar zenith angles and is almost independent from the ground albedo. Thus this technique is very well suited for observations in polar regions close to the solar terminator. For large periods of our measurements the solar elevation was very low or even below the horizon. For such conditions, most reactive Br-compounds might exist as Br2 molecules and ozone destruction and the removal of reactive bromine compounds might be substantially reduced.

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