Keywords
turbulent heat fluxes; marginal ice zone (MIZ); atmospheric boundary layer (ABL); air-sea interaction; Arctic; UAS; eddy covariance (EC); Doppler wind lidar; ship-based operations
Presenter Abstract
The turbulent heat exchange across the marginal ice zone (MIZ) is characterized by substantial flux gradients between open water and solid ice. Near polynyas and leads, existing bulk flux approaches break down, leading to unreliable flux estimates. Direct turbulent flux measurements across the MIZ remain sparse; existing measurement approaches, such as eddy-covariance systems, are either static and logistically impractical (ice-deployed) or suffer from flow distortion (ship-borne). Neither approach can systematically sample fluxes across varying ice conditions within one campaign.
The SAMURAI-S system---a heavy-lifting octocopter carrying a sonic anemometer on a payload suspended \SI{20}{\m} below the rotor plane---has been validated against tower-based measurements. This system was successfully employed during the ROVER-25 winter cruise in the MIZ of the Greenland Sea, to characterize the ABL and fluxes across varying sea ice conditions. SAMURAI-S measurements were complemented by \qty{2} ship-borne lidars (profiling and scanning), providing continuous boundary-layer wind and turbulence profiles. During this 5-week cruise aboard the R/V Kronprins Haakon, \qty{11} transects were performed across the MIZ, from pack ice through open ocean. Vertical profiling and hovering flights of \qtyrange[range-units = single]{20}{35}{\minute} were carried out from the helicopter deck. We performed \qty{20} measurement flights under challenging conditions, including strong ship motion, icing, poor visibility and fog, as well as temperatures down to \SI{-20}{\degreeCelsius} and winds up to \SI{12}{\m \per \s}. The observed turbulent sensible heat fluxes ranged from \SI{-10}{\W \per \square \m} over sea ice to \SI{45}{\W \per \square \m} over open water. Vertical velocity observations from SAMURAI-S were used to validate motion correction strategies for lidar observations. The presented combined ship-based approach enables spatially distributed flux measurements across heterogeneous ice from a flexible platform, enabling systematic ABL observations in polar regions, with implications for constraining the air-sea heat exchange that drives deep water formation.
Presentations
Presented in Session 9: Field Campaigns
SAMURAI in the Arctic - Turbulent Flux Measurements across the Marginal Ice Zone from R/V Kronprins Haakon
The turbulent heat exchange across the marginal ice zone (MIZ) is characterized by substantial flux gradients between open water and solid ice. Near polynyas and leads, existing bulk flux approaches break down, leading to unreliable flux estimates. Direct turbulent flux measurements across the MIZ remain sparse; existing measurement approaches, such as eddy-covariance systems, are either static and logistically impractical (ice-deployed) or suffer from flow distortion (ship-borne). Neither approach can systematically sample fluxes across varying ice conditions within one campaign.
The SAMURAI-S system---a heavy-lifting octocopter carrying a sonic anemometer on a payload suspended \SI{20}{\m} below the rotor plane---has been validated against tower-based measurements. This system was successfully employed during the ROVER-25 winter cruise in the MIZ of the Greenland Sea, to characterize the ABL and fluxes across varying sea ice conditions. SAMURAI-S measurements were complemented by \qty{2} ship-borne lidars (profiling and scanning), providing continuous boundary-layer wind and turbulence profiles. During this 5-week cruise aboard the R/V Kronprins Haakon, \qty{11} transects were performed across the MIZ, from pack ice through open ocean. Vertical profiling and hovering flights of \qtyrange[range-units = single]{20}{35}{\minute} were carried out from the helicopter deck. We performed \qty{20} measurement flights under challenging conditions, including strong ship motion, icing, poor visibility and fog, as well as temperatures down to \SI{-20}{\degreeCelsius} and winds up to \SI{12}{\m \per \s}. The observed turbulent sensible heat fluxes ranged from \SI{-10}{\W \per \square \m} over sea ice to \SI{45}{\W \per \square \m} over open water. Vertical velocity observations from SAMURAI-S were used to validate motion correction strategies for lidar observations. The presented combined ship-based approach enables spatially distributed flux measurements across heterogeneous ice from a flexible platform, enabling systematic ABL observations in polar regions, with implications for constraining the air-sea heat exchange that drives deep water formation.