Observations and characteristics of the Ice-Ocean Boundary Layer in McMurdo Sound, Antarctica

Ryan Beecroft, Remo Cossu, Alexander Forrest, Ian Hawes, Charles LEMCKERT

Research output: Contribution to conference (non-published works)Paper

Abstract


Observation and analysis of Antarctic ice-ocean boundary layer formation is crucial to understanding paramount physical and biological interactions between sea-ice and ocean waters. Velocity measurements were made in November 2014 using Acoustic Doppler Current Profilers (ADCPs) moored in ~2m thick first year sea-ice in McMurdo Sound, Antarctica. Additionally, ADCPs mounted to an Autonomous Underwater Vehicle (AUV) were used to profile horizontal transects of up to 500m in length at 6-8m below the ice-ocean interface. A diurnal tidal cycle was observed with the stationary ADCP with maximum horizontal velocities in the range of 0.16-0.18ms-1. Laminar sub-layer thicknesses of up to 12m were identifiable from the stationary ADCP measurements over various stages of the tidal cycle, with the most pronounced velocity profiles corresponding to the flood tide events in McMurdo Sound. The first ever comparison under-ice of stationary ADCP and AUV mounted ADCP measurements yields a relatively good agreement of the under-ice velocity distribution during periods of maximum flow velocity; yet velocity variability of the AUV measurements (0.07-0.15ms-1) are considerably higher than those recorded by the stationary ADCP (0.01ms-1). Ultimately, this study provides a comparison of stationary ADCP and AUV mounted ADCP measurements, with the aim of fortifying the application of AUVs in under-ice environments. In particular, this is critical for measurements within the highly dynamic boundary layer region close to the under-ice surface, which have proven difficult to observe through conventional methods. The study focuses on velocity measurements within the first 25m beneath the ice, coinciding with physical measurements (temperature, salinity and density) to describe the observed boundary layer characteristics
Original languageEnglish
Pages1-12
Number of pages12
Publication statusPublished - 2016
Externally publishedYes
EventIAHR International Symposium on Ice - Ann Arbor, Michigan, United States
Duration: 31 May 20163 Jun 2016
Conference number: 23rd
http://iahr-ice2016.org/

Conference

ConferenceIAHR International Symposium on Ice
CountryUnited States
CityMichigan
Period31/05/163/06/16
Internet address

Fingerprint

Acoustic Doppler Current Profiler
boundary layer
autonomous underwater vehicle
ice
ocean
tidal cycle
epontic environment
sea ice
Antarctica
velocity profile
flow velocity
tide
transect
salinity

Cite this

Beecroft, R., Cossu, R., Forrest, A., Hawes, I., & LEMCKERT, C. (2016). Observations and characteristics of the Ice-Ocean Boundary Layer in McMurdo Sound, Antarctica. 1-12. Paper presented at IAHR International Symposium on Ice, Michigan, United States.
Beecroft, Ryan ; Cossu, Remo ; Forrest, Alexander ; Hawes, Ian ; LEMCKERT, Charles. / Observations and characteristics of the Ice-Ocean Boundary Layer in McMurdo Sound, Antarctica. Paper presented at IAHR International Symposium on Ice, Michigan, United States.12 p.
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Beecroft, R, Cossu, R, Forrest, A, Hawes, I & LEMCKERT, C 2016, 'Observations and characteristics of the Ice-Ocean Boundary Layer in McMurdo Sound, Antarctica' Paper presented at IAHR International Symposium on Ice, Michigan, United States, 31/05/16 - 3/06/16, pp. 1-12.

Observations and characteristics of the Ice-Ocean Boundary Layer in McMurdo Sound, Antarctica. / Beecroft, Ryan; Cossu, Remo; Forrest, Alexander ; Hawes, Ian; LEMCKERT, Charles.

2016. 1-12 Paper presented at IAHR International Symposium on Ice, Michigan, United States.

Research output: Contribution to conference (non-published works)Paper

TY - CONF

T1 - Observations and characteristics of the Ice-Ocean Boundary Layer in McMurdo Sound, Antarctica

AU - Beecroft, Ryan

AU - Cossu, Remo

AU - Forrest, Alexander

AU - Hawes, Ian

AU - LEMCKERT, Charles

PY - 2016

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N2 - Observation and analysis of Antarctic ice-ocean boundary layer formation is crucial to understanding paramount physical and biological interactions between sea-ice and ocean waters. Velocity measurements were made in November 2014 using Acoustic Doppler Current Profilers (ADCPs) moored in ~2m thick first year sea-ice in McMurdo Sound, Antarctica. Additionally, ADCPs mounted to an Autonomous Underwater Vehicle (AUV) were used to profile horizontal transects of up to 500m in length at 6-8m below the ice-ocean interface. A diurnal tidal cycle was observed with the stationary ADCP with maximum horizontal velocities in the range of 0.16-0.18ms-1. Laminar sub-layer thicknesses of up to 12m were identifiable from the stationary ADCP measurements over various stages of the tidal cycle, with the most pronounced velocity profiles corresponding to the flood tide events in McMurdo Sound. The first ever comparison under-ice of stationary ADCP and AUV mounted ADCP measurements yields a relatively good agreement of the under-ice velocity distribution during periods of maximum flow velocity; yet velocity variability of the AUV measurements (0.07-0.15ms-1) are considerably higher than those recorded by the stationary ADCP (0.01ms-1). Ultimately, this study provides a comparison of stationary ADCP and AUV mounted ADCP measurements, with the aim of fortifying the application of AUVs in under-ice environments. In particular, this is critical for measurements within the highly dynamic boundary layer region close to the under-ice surface, which have proven difficult to observe through conventional methods. The study focuses on velocity measurements within the first 25m beneath the ice, coinciding with physical measurements (temperature, salinity and density) to describe the observed boundary layer characteristics

AB - Observation and analysis of Antarctic ice-ocean boundary layer formation is crucial to understanding paramount physical and biological interactions between sea-ice and ocean waters. Velocity measurements were made in November 2014 using Acoustic Doppler Current Profilers (ADCPs) moored in ~2m thick first year sea-ice in McMurdo Sound, Antarctica. Additionally, ADCPs mounted to an Autonomous Underwater Vehicle (AUV) were used to profile horizontal transects of up to 500m in length at 6-8m below the ice-ocean interface. A diurnal tidal cycle was observed with the stationary ADCP with maximum horizontal velocities in the range of 0.16-0.18ms-1. Laminar sub-layer thicknesses of up to 12m were identifiable from the stationary ADCP measurements over various stages of the tidal cycle, with the most pronounced velocity profiles corresponding to the flood tide events in McMurdo Sound. The first ever comparison under-ice of stationary ADCP and AUV mounted ADCP measurements yields a relatively good agreement of the under-ice velocity distribution during periods of maximum flow velocity; yet velocity variability of the AUV measurements (0.07-0.15ms-1) are considerably higher than those recorded by the stationary ADCP (0.01ms-1). Ultimately, this study provides a comparison of stationary ADCP and AUV mounted ADCP measurements, with the aim of fortifying the application of AUVs in under-ice environments. In particular, this is critical for measurements within the highly dynamic boundary layer region close to the under-ice surface, which have proven difficult to observe through conventional methods. The study focuses on velocity measurements within the first 25m beneath the ice, coinciding with physical measurements (temperature, salinity and density) to describe the observed boundary layer characteristics

KW - ice

KW - oceanography

KW - mixing

KW - Antarctic Ice Sheet

M3 - Paper

SP - 1

EP - 12

ER -

Beecroft R, Cossu R, Forrest A, Hawes I, LEMCKERT C. Observations and characteristics of the Ice-Ocean Boundary Layer in McMurdo Sound, Antarctica. 2016. Paper presented at IAHR International Symposium on Ice, Michigan, United States.