So very high values occur if the thermistor is surrounded by calm air, less so when it's windy. and then snow also gives relatively high values.
Agreed, though the snow layer may be slushy and the composition of the layer between ocean surface and ice freeboard may complicate interpretation.
Still don't get what that -0.6m high-ish value (1.1⁰C) feature is, or rather why a melt pond (trapped water) would give high-ish values...
Unless it's that the low 0.6⁰C values are for ice near melting point 
(i.e. thermistor is kept cool by phase change)
Tend to agree, the melt pond appears to be freezing slowly.
And then the lowest values (0.4-0.5⁰C) happen in water with a current (forced convection). 0.7 for water with no current (free convection), and back to 1.1 at the ice-ocean interface with no current (no room above for heat to convect away)
Might be interesting to overlay 0200h drift speed to see if it correlates with the higher ocean heat120 temps. Could air temp too.
A couple of papers featuring SIMBAs that may help.
Snow depth and ice thickness derived from SIMBA ice mass balance buoy data using an automated algorithmZeliang Liao, Bin Cheng, JieChen Zhao, Timo Vihma, Keith Jackson, Qinghua
Yang, Yu Yang, Lin Zhang, Zhijun Li, Yubao Qiu & Xiao Cheng
https://doi.org/10.1080/17538947.2018.1545877extract:
3.2. Heating temperature regimen
Each sensor on the SIMBA thermistor chain has a heating element. A small (8 V) voltage was applied
to the resistors so that the heat energy liberated in the vicinity of each sensor would be the same. The
heating time interval typically lasted from 60 to 120 s. The sensor temperatures usually rise by varying
amounts along the thermistor chain based on whether their locations are in air, snow, ice, or water. In
practice, however, the temperature changes may not be clear enough to detect the air/snow, snow/ice,
and ice/water interfaces (Jackson et al. 2013). Consider buoy A as an example, the sensor temperature
reading after 120 s of heating is plotted in Figure 6. Visual inspection reveals very weak discrimination
of air/snow and ice/water interfaces from the colour pattern (Figure 7(a)). In June, the heating tem-
perature showed no changes, but errors were probably encountered. The strong warm-up of the in-
ice (∼1 m depth) in late December and mid-February (1 m –1.5 m depth) remain unknown.
The heating temperature also revealed two horizontal discriminated interfaces at 0 m and –
0.22 m in depth below the surface. The 0 m level was the original snow/ice interface. The second
interface (white broken line in Figure 6(a)) is the original sea water level. The initial ice was thick
(1.44 m), creating strong buoyancy that kept the upper part of the ice column above the water
level. When SIMBA was deployed, the freeboard was 21 cm positive (sea water level was below
ice surface), and this agreed well with the white broken line in Figure 7(a). When the SIMBA ther-
mistor string was deployed, the positive freeboard introduced a segment of empty boreholes between
sea level and the ice surface. This part of a borehole is usually filled with snow-slush or perhaps left
open. This layer, in this case at 21 cm in depth, was actually an intermediate mixture layer with
snow/slush and water. It takes time to completely refreeze and integrate with the ice column com-
posed by freezing sea water in the borehole below sea level. In extreme conditions, the upper bore-
hole may have had difficulty in fully refreezing if there was no water in the upper portion.
If the algorithm-retrieved air/snow (5-day running mean) is superimposed on the ice/water inter-
face in the heating temperature regimen (Figure 7(b)), the algorithm calculated interfaces are in good
agreement with the heating temperature discriminated interfaces. The heating temperature pattern
could discriminate interfaces. However, the discrimination was sometimes very weak, and it was
difficult to identify and obtain an entire time series of the interfaces.
-------------------------------------
Discrimination Algorithm and Procedure of Snow Depth and Sea Ice Thickness Determination Using Measurements of the Vertical Ice Temperature Profile by the Ice-Tethered BuoysGuangyu Zuo, Yinke Dou,1, and Ruibo Lei2
Published online 2018 Nov 27. doi: 10.3390/s18124162
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6308795/extract:
In cases without the deployment of the acoustic sounding instruments, the vertical temperature profile through the air, snow, ice, and upper ocean can be used to discriminate snow depth and ice thickness because both the specific heats and the heat conduction coefficients are very different among air, snow, ice and water [19,20]. Generally, the vertical temperature profile measured by ice-tethered buoys has two main change points on the top and lower interfaces of the layer of snow-covered ice and the temperature profiles segmented by these two change points show remarkable differences in vertical gradient, daily amplitude, and seasonal evolution. The interface between snow and sea ice is vague because the formation of snow-ice or a slush layer cannot be distinctly identified using only the temperature profile [21,22]. The theories of change point and maximum likelihood are considered optimization methods to implement signal segmentation for identification purposes and can be used to determine the snow depth and sea ice thickness by identifying the change points of the sea ice temperature profile.
.1.1. Interface between Air and Snow or Sea Ice
The evolution of snow depth over sea ice may be affected by synoptic processes phenomena such as storms, snowfall, and sleet, or due to melting caused by solar radiation. Thus, the temporal fluctuations of snow depth are much larger than for sea ice thickness. The daily amplitude of temperature profiles and the vertical gradients of temperature were examined because, in some cases, it was difficult to accurately distinguish the top interface by using the measurements of the temperature alone. From the data of the daily amplitude of temperature profiles and the vertical gradients of temperature, we checked the corresponding values one by one from the top of the temperature profiles to find the change points.
3.1.2. Interface between Ice and Ocean
To identify the lower ice interface (ice-ocean interface), temperature profiles for the lower ice layer were obtained from some thermistors near the bottom of the sea ice. The seawater temperature was determined using the lower five thermistors, which generally had a negligible temperature gradient from the bottom of the sea ice. The points where the temperature profile of the lower ice layer intersected the ocean temperature were regarded as the ice-ocean interface (Figure 3b). The ice-ocean interface determined by the method of seeking described above had a good accuracy in winter or sea ice growth period. This method became unreliable in summer, especially in ice melting period when the temperature gradient across the lower interface weakened. In summer, the temperature profile of sea ice became nonlinear with a C-shaped curve. Then the lower ice interface was determined from the obvious inflection point in the vertical C-shaped ice temperature profile (Figure 3d). In winter, temperature profile of sea ice remained linear and temperature of the basal ice layer was colder than the upper ocean. There will be a sharp inflection point occurring at the interface. Thus, ice-ocean interface can be estimated from the vertical gradients of sea ice temperature profile.
