Good question JTivat and something I was wondering myself while up in Tobermory a few weekends ago in water at 39 F. My personal observations tend to concur with Cat's as well.
In Carl Edmond's book "Diving and Subaquatic Medicine" there is only one reference to cold and nitrogen narcosis.
"Other factors have been observed to effect the degree of narcosis. Alcohol, fatigue, anxiety, cold, reduced sensory input, and oxygen and carbon dioxide disturbances are interrelated in impairing the diver's undererwater ability."
In Cat's diver above from Florida there may have been a few of those factors like fatigue (traveling), anxiety (new dive environment), cold (Lake Superior is always cold and if the diver does not have proper thermal protection his core will cool quickly), reduced sensory input (diver having to wear hood and gloves), and CO2 disturbances (anxiety may cause faster shallower breathing with increased pp of CO2 which is additive to the increased N2 tension effects) which all acted to predispose the diver to nitrogen narcosis in the cold water whereas at the same depth in warm water he was fine. Last summer I witnessed a similar scenerio in a visiting diver from Brazil who became quite narced in 80 foot cold Toby water. Likely was multifactorial as well with regards to the cause. I wonder if research has been done on narcosis using dry hyperbaric chamber dives, cold ambient air, rectal temp probes and all?
As for the effects of narcosis though on hypothermia Bennett and Elliot's "Physiology and Medicine of Diving" states, " this study proved conclusively that divers breathing compressed air are predisposed to hypothermia, due to the inhibitory efffect of inert gas narcosis on shivering." In other words the increased ppN2 inhibits one's ability to raise core temperature by shivering which further increases a diver's risk of hypothermia.
It appears then that the diver above was likely in a dangerous positive feedback loop whereby his poor thermal protection and other factors allowed him to become 'narced' and this narcosis impaired his shivering thermogenesis response which then further worsened the narcosis. Thermal perception according to Bennet is also severely blunted by high N2 levels. The only way out of this lethal loop was to immediately lower his exposure to high partial pressure of nitrogen by moving him to a shallower depth.
Had it not been for this diver's very attentive properly dressed buddies he likely would have carried on merrily down the slope only to disappear out of sight permanently.