# Investigations into Frost Flower Physical Characteristics and the C-Band Scattering Response
## 4 Conclusions  
We investigated the C-band scattering signatures and physical properties of frost-flower-covered sea ice at the SERF located at the University of Manitoba. We presented and analyzed physical characteristics, which evaluated the measured scattering response at multiple incidence angles of the C-band and examined how the physical characteristics of an evolving sea ice surface eventually covered in frost flowers gave rise to its scattering response over time. The sea ice surface was initially extremely smooth and devoid of a liquid brine skim during Stage 1 of this experiment and consequently frost flowers were not formed despite theoretically appropriate meteorological conditions (low air temperature, low near-surface wind speed, and high near-surface relative humidity). This provides evidence for the presence of (i) liquid brine at the surface and (ii) raised nodules as nucleation points potentially enabling frost flower initiation. Frost flowers began to form when we observed frost smoke due to brine expulsion. The surface temperature decreased rapidly to its minimum for the experimental period upon a marginal increase in the near-surface wind speed. A liquid brine skim was observed on the surface of the sea ice while the frost flower coverage increased. The formation of frost flowers and their subsequent coverage of the sea ice surface occurred over the six hours directly following these observed changes at the surface. The sea ice surface salinity increased by more than a factor of three. The C-band NRCS measurements substantially increased, which coincided with the appearance of the liquid brine skim and subsequent frost flower formation at the surface. We observed a minor short-term minimum NRCS at 25\({}^{\circ}\) incidence as the lower layers of the frost flowers became brine-soaked and the sea ice surface salinity rapidly increased. The effect was less distinct with higher incidence angles. Our measurements indicate that the brine expulsion phase and frost flower salinization can have substantial temporal variability (i.e., there are differences between previous experiments [19] and this experiment), which can be detected by scatterometer time-series measurements. We can confirm that low incidence angles (25\({}^{\circ}\)) are most sensitive to physical and thermodynamic changes in frost flower covered sea ice. The observations and measurements of the delayed brine expulsion provide unique experimental data, which enhance our understanding of frost flowers and sea ice growth processes. Further work is required to understand the timing of brine expulsion at the surface of the sea ice and its effects on frost flower growth processes and their ensuing salinization. In the future, evaluating surface roughness in advance of initial frost flower formation should occur to assess the development and effect of nucleation sites on the eventual initiation and proliferation of frost flowers. Polarimetric scattering measurements and their interpretation must be part of future experimental work. Contemporary satellite constellation missions are designed to obtain high spatial resolution imagery with higher revisit frequency than single satellites. However, the images are collected at a relatively low temporal resolution when compared to the rapid geophysical changes observed in this experiment. Therefore, the results from this high-temporal resolution remote sensing experiment can be used to interpret and predict the time-series microwave scattering signatures between satellite imaging operations, which are instrumental for understanding processes in the changing Arctic. [PERSON], [PERSON], and [PERSON] were responsible for the study conceptualization. [PERSON], [PERSON], [PERSON], and [PERSON] handled the methodology. [PERSON], [PERSON], [PERSON], and [PERSON] managed the software. [PERSON], [PERSON], [PERSON], and [PERSON] validated the results. [PERSON], [PERSON], [PERSON], and [PERSON] took part in formal analysis. [PERSON] and [PERSON] managed the resources. [PERSON] curated data.