Can katabatic winds directly force retreat of Greenland outlet glaciers? Hypothesis test on Helheim Glacier in Sermilik Fjord

Abstract. Katabatic winds drive sea ice export from glaciated fjords across Greenland and other high latitude environments, but few studies have investigated the extent to which they also drive inflow of warm water and whether they have a direct impact on glaciers stability. Using ERA5 reanalysis data, verified by two local weather stations, we create a timeseries of katabatic winds across Sermilik Fjord in southeast Greenland. Using this along with hydrographic data, from 2009–2013, positioned across the fjord, we analyse changes in fjord circulation during individual katabatic flows. Changes in melange presence are analysed too, via the use of MODIS and Landsat-7 satellite imagery. We show that warm water influxes are associated with katabatic winds, and that the potential submarine melt rates vary up to four-fold, dependant on katabatic wind strength. Rapid retreat of Helheim Glacier occurred during strong downslope wind events which removed the ice melange, and so the well documented retreat of Helheim between 2001–2005 is predicted to be in part because of strong katabatic winds. Removal of the ice-melange led to a series of calving events, driven by a lack of buttressing and weakness propagation up the glacier causing a retreat of up to 1.5 km. In contrast to previous research in which katabatic winds were seen as having an indirect influence on glaciers, we report direct forcing on Helheim Glacier through episodes of retreat occurring in response to inflow of warm water masses and removal of proglacial ice melange after downslope wind events.

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Little Ice Age climate and oceanic conditions of the Ross Sea, Antarctica from a coastal ice core record

Climate of the Past ◽

10.5194/cp-8-1223-2012 ◽

2012 ◽

Vol 8 (4) ◽

pp. 1223-1238 ◽

Cited By ~ 33

Author(s):

R. H. Rhodes ◽

N. A. N. Bertler ◽

J. A. Baker ◽

H. C. Steen-Larsen ◽

S. B. Sneed ◽

...

Keyword(s):

Little Ice Age ◽

Ross Sea ◽

Global Climate ◽

Ice Core ◽

Ice Age ◽

Katabatic Wind ◽

Aeolian Transport ◽

Katabatic Winds ◽

Order Of Magnitude ◽

Wind Events

Abstract. Increasing paleoclimatic evidence suggests that the Little Ice Age (LIA) was a global climate change event. Understanding the forcings and associated climate system feedbacks of the LIA is made difficult by the scarcity of Southern Hemisphere paleoclimate records. We use a new glaciochemical record of a coastal ice core from Mt. Erebus Saddle, Antarctica, to reconstruct atmospheric and oceanic conditions in the Ross Sea sector of Antarctica over the past five centuries. The LIA is identified in stable isotope (δD) and lithophile element records, which respectively demonstrate that the region experienced 1.6 ± 1.4 °C cooler average temperatures prior to 1850 AD than during the last 150 yr and strong (>57 m s−1) prevailing katabatic winds between 1500 and 1800 AD. Al and Ti concentration increases of an order of magnitude (>120 ppb Al) are linked to enhanced aeolian transport of complex silicate minerals and represent the strongest katabatic wind events of the LIA. These events are associated with three 12–30 yr intervals of cooler temperatures at ca. 1690 AD, 1770 AD and 1840 AD. Furthermore, ice core concentrations of the biogenic sulphur species MS− suggest that biological productivity in the Ross Sea polynya was ~80% higher prior to 1875 AD than at any subsequent time. We propose that cooler Antarctic temperatures promoted stronger katabatic winds across the Ross Ice Shelf, resulting in an enlarged Ross Sea polynya during the LIA.

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The Atmospheric Boundary Layer and Surface Conditions during Katabatic Wind Events over the Terra Nova Bay Polynya

Remote Sensing ◽

10.3390/rs12244160 ◽

2020 ◽

Vol 12 (24) ◽

pp. 4160

Author(s):

Marta Wenta ◽

John J. Cassano

Keyword(s):

Open Water ◽

Unmanned Aircraft ◽

Katabatic Wind ◽

Katabatic Winds ◽

Surface Conditions ◽

Terra Nova Bay ◽

Coastal Polynya ◽

Terra Nova ◽

Wind Events ◽

Aircraft System

Off the coast of Victoria Land, Antarctica an area of open water—the Terra Nova Bay Polynya (TNBP)—persists throughout the austral winter. The development of this coastal polynya is driven by extreme katabatic winds blowing down the slopes of Transantarctic Mountains. The surface-atmosphere coupling and ABL transformation during the katabatic wind events between 18 and 25 September 2012 in Terra Nova Bay are studied, using observations from Aerosonde unmanned aircraft system (UAS), numerical modeling results and Antarctic Weather Station (AWS) measurements. First, we analyze how the persistence and strength of the katabatic winds relate to sea level pressure (SLP) changes in the region throughout the studied period. Secondly, the polynya extent variations are analysed in relation to wind speed changes. We conclude that the intensity of the flow, surface conditions in the bay and regional SLP fluctuations are all interconnected and contribute to polynya development. We also analyse the Antarctic Mesoscale Prediction System (AMPS) forecast for the studied period and find out that incorrect representation of vertical ABL properties over the TNBP might be caused by overestimated sea ice concentrations (SIC) used as model input. Altogether, this research provides a unique description of TNBP development and its interactions with the atmosphere and katabatic winds.

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Little Ice Age climate and oceanic conditions of the Ross Sea, Antarctica from a coastal ice core record

Climate of the Past Discussions ◽

10.5194/cpd-8-215-2012 ◽

2012 ◽

Vol 8 (1) ◽

pp. 215-262 ◽

Cited By ~ 4

Author(s):

R. H. Rhodes ◽

N. A. N. Bertler ◽

J. A. Baker ◽

H. C. Steen-Larsen ◽

S. B. Sneed ◽

...

Keyword(s):

Little Ice Age ◽

Bottom Water ◽

Ross Sea ◽

Ice Core ◽

Ice Age ◽

Katabatic Wind ◽

Katabatic Winds ◽

Ross Ice Shelf ◽

Order Of Magnitude ◽

Wind Events

Abstract. The Little Ice Age (LIA) is the most recent abrupt climate change event. Understanding its forcings and associated climate system feedbacks is made difficult by a scarcity of Southern Hemisphere paleoclimate records. In this paper we utilise ice core glaciochemical records to reconstruct atmospheric and oceanic conditions in the Ross Sea sector of Antarctic, a region influenced by two contrasting meteorological regimes: katabatic winds and cyclones. Stable isotope (δD) and lithophile element concentration (e.g., Al) records indicate that the region experienced ~1.75 °C cooler temperatures and strong (>57 m s−1) prevailing katabatic winds during the LIA. We observe that the 1590–1875 record is characterised by high d-excess values and marine element (e.g., Na) concentrations, which are linked to the intrusion of cyclonic systems. The strongest katabatic wind events of the LIA, marked by Al, Ti and Pb concentration increases of an order of magnitude (>120 ppb Al), also occur during this interval. Furthermore, concentrations of the biogenic sulphur species MS− suggest that biological productivity in the Ross Sea Polynya was ~80% higher prior to 1875 than in the subsequent time. We propose that colder temperatures and intensified cyclonic activity in the Ross Sea promoted stronger katabatic winds across the Ross Ice Shelf, resulting in an enlarged polynya with increased sea ice and bottom water production. It is therefore hypothesised that increased bottom water formation during the LIA occurred in response to atmospheric circulation change.

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Subglacial brine flow and wind-induced internal waves in Lake Bonney, Antarctica

Antarctic Science ◽

10.1017/s0954102020000036 ◽

2020 ◽

Vol 32 (3) ◽

pp. 223-237

Author(s):

Jade P. Lawrence ◽

Peter T. Doran ◽

Luke A. Winslow ◽

John C. Priscu

Keyword(s):

Water Column ◽

Internal Waves ◽

Open Water ◽

Surface Discharge ◽

Katabatic Wind ◽

Neutral Buoyancy ◽

Cold Temperatures ◽

Glacier Terminus ◽

Wind Events ◽

Taylor Glacier

AbstractBrine beneath Taylor Glacier has been proposed to enter the proglacial west lobe of Lake Bonney (WLB) as well as from Blood Falls, a surface discharge point at the Taylor Glacier terminus. The brine strongly influences the geochemistry of the water column of WLB. Year-round measurements from this study are the first to definitively identify brine intrusions from a subglacial entry point into WLB. Furthermore, we excluded input from Blood Falls by focusing on winter dynamics when the absence of an open water moat prevents surface brine entry. Due to the extremely high salinities below the chemocline in WLB, density stratification is dominated by salinity, and temperature can be used as a passive tracer. Cold brine intrusions enter WLB at the glacier face and intrude into the water column at the depth of neutral buoyancy, where they can be identified by anomalously cold temperatures at that depth. High-resolution measurements also reveal under-ice internal waves associated with katabatic wind events, a novel finding that challenges long-held assumptions about the stability of the WLB water column.

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Estimates of direct radiative forcing due to aerosols from the MERRA-2 reanalysis over the Amazon region

10.5194/acp-2018-355 ◽

2018 ◽

Cited By ~ 1

Author(s):

Brunna Penna ◽

Dirceu Herdies ◽

Simone Costa

Keyword(s):

Radiative Forcing ◽

Reanalysis Data ◽

Amazon Region ◽

Reference State ◽

Aerosol Radiative Forcing ◽

Aerosol Loading ◽

Direct Radiative Forcing ◽

Direct Forcing ◽

The Difference ◽

Natural Aerosols

Abstract. Sixteen years of analysis of clear-sky direct aerosol radiative forcing is presented for the Amazon region, with calculations of AERONET network, MODIS sensor and MERRA-2 reanalysis data. The results showed that MERRA-2 reanalysis is an excellent tool for calculating and providing the spatial distribution of aerosol direct radiative forcing. In addition, the difference between considering the reference state of the atmosphere without aerosol loading and with natural aerosol to obtain the aerosol direct radiative forcing is discussed. During the dry season, the monthly average direct forcing at the top of atmosphere varied from −9.60 to −4.20 Wm−2, and at the surface, it varied from −29.81 to −9.24 Wm−2, according to MERRA-2 reanalysis data and the reference state of atmosphere without aerosol loading. Already with the state of reference being the natural aerosols, the average direct forcing at the top of atmosphere varied from −5.15 to −1.18 Wm−2, and at the surface, it varied from −21.28 to −5.25 Wm−2; this difference was associated with the absorption of aerosols.

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Observations of the Antarctic ice sheet with the Seasat scatterometer: relation to katabatic-wind intensity and direction

Journal of Glaciology ◽

10.3189/s002214300001604x ◽

1993 ◽

Vol 39 (132) ◽

pp. 385-396

Author(s):

M. Ledroit ◽

F. Remy ◽

J.-F. Minster

Keyword(s):

Incidence Angle ◽

Ice Sheet ◽

Katabatic Wind ◽

Katabatic Winds ◽

Antarctic Ice Sheet ◽

Scatter Coefficient ◽

Low Incidence ◽

Ocean Wind ◽

Wind Intensity ◽

The Antarctic

AbstractThe Seasat A satellite scatterometer radar, initially designed to measure ocean-wind intensity and direction, also provided observations on the Antarctic ice sheet. The signal of the back-scatter coefficient decreases strongly from 10 to −20 dB when the incidence angle of the observations increases from 0° to 65°. An additional 5 dB signal is found, which is correlated with the direction and intensity of katabatic winds, independent of the incidence angle and polarization of the signal. By using simplified models of the volume-scattering within the snowpack (which is mostly sensitive to snow grain-size) and surface-scattering from the air-snow interface (which depends on roughness), it is evident that the signal of the scatterometer could result from the effects of snow dunes at low incidence angle, and of micro-roughness and volume back-scatter at incidence angles greater than 25°. The instrument therefore provides a means of measuring the direction and intensity of katabatic winds.

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Evaluating the Experimental High-Resolution Rapid Refresh–Alaska Modeling System Using USArray Pressure Observations

Weather and Forecasting ◽

10.1175/waf-d-17-0155.1 ◽

2018 ◽

Vol 33 (4) ◽

pp. 933-953 ◽

Cited By ~ 4

Author(s):

Taylor A. McCorkle ◽

John D. Horel ◽

Alexander A. Jacques ◽

Trevor Alcott

Keyword(s):

High Resolution ◽

Surface Pressure ◽

Weather Conditions ◽

Horizontal Resolution ◽

Production Cycle ◽

Downslope Winds ◽

Downslope Wind ◽

Wind Events ◽

Environmental Prediction ◽

Mean Square Errors

Abstract The High-Resolution Rapid Refresh–Alaska (HRRR-AK) modeling system provides 3-km horizontal resolution and 0–36-h forecast guidance for weather conditions over Alaska. This study evaluated the experimental version of the HRRR-AK system available from December 2016 to June 2017, prior to its operational deployment by the National Centers for Environmental Prediction in July 2018. Surface pressure observations from 158 National Weather Service (NWS) stations assimilated during the model’s production cycle and pressure observations from 101 USArray Transportable Array (TA) stations that were not assimilated were used to evaluate 265 complete 0–36-h forecasts of the altimeter setting (surface pressure reduced to sea level). The TA network is the largest recent expansion of Alaskan weather observations and provides an independent evaluation of the model’s performance during this period. Throughout the study period, systematic differences in altimeter setting between the HRRR-AK 0-h forecasts were larger relative to the unassimilated TA observations than relative to the assimilated NWS observations. Upon removal of these initial biases from each of the subsequent 1–36-h altimeter setting forecasts, the model’s 36-h forecast root-mean-square errors at the NWS and TA locations were comparable. The model’s treatment of rapid warming and downslope winds that developed in the lee of the Alaska Range during 12–15 February is examined. The HRRR-AK 0-h forecasts were used to diagnose the synoptic and mesoscale conditions during this period. The model forecasts underestimated the abrupt increases in the temperature and intensity of the downslope winds with smaller errors as the downslope wind events evolved.

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WRF simulation of downslope wind events in coastal Santa Barbara County

Atmospheric Research ◽

10.1016/j.atmosres.2017.03.010 ◽

2017 ◽

Vol 191 ◽

pp. 57-73 ◽

Cited By ~ 10

Author(s):

Forest Cannon ◽

Leila M.V. Carvalho ◽

Charles Jones ◽

Todd Hall ◽

David Gomberg ◽

...

Keyword(s):

Santa Barbara ◽

Downslope Wind ◽

Santa Barbara County ◽

Wind Events

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A pilot study on the interactions between katabatic winds and polynyas at the Adélie Coast, eastern Antarctica

Antarctic Science ◽

10.1017/s0954102095000423 ◽

1995 ◽

Vol 7 (3) ◽

pp. 307-314 ◽

Cited By ~ 36

Author(s):

Ute Adolphs ◽

Gerd Wendler

Keyword(s):

Sea Ice ◽

Open Water ◽

Katabatic Wind ◽

Data Sets ◽

Strong Wind ◽

Coastal Sea ◽

Coastal Winds ◽

Temperature Contrast ◽

Wind Events ◽

Anomalous Wind

Infrared satellite images of the coastal area off Adélie Land were examined together with two wind data sets, one from the manned French station, Dumont d'Urville, the other one from an Automatic Weather Station (AWS) during the 1986 austral winter. A correlation between the development of open water areas (polynyas) and the appearance of extremely strong offshore winds can be drawn. The wind direction tended to be more perpendicular to the coastline during these extreme ‘events’, suggesting a katabatic origin of the increase in wind strength. In the study area the influence of the katabatic wind on the sea ice extends 20–100 km offshore. Sea ice motion further off the coast seems to be more dominated by synoptic scale weather systems. Broader scale atmospheric influences may create large polynya structures which influence the development of coastal winds, as the temperature contrast between open water and the cold continent generates its own circulation. Strong wind events can have a weakening effect on the coastal sea ice which can lead to a much more sensitive reaction of the sea ice in response to following anomalous wind events.

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