Subject: Can hair manufacture more melanin due to sun exposure?

I actually have two questions about hair here. I know this sounds crazy, but 
when I am living Brasil, (I live off and on there for years at a time ), 
instead of my hair actually bleaching out from the harsh near- equatorial sun 
and salt water, my hair gets much darker in color and thicker. Could this be 
some kind of protection my body does to protect my scalp from the sun's rays 
and heat?? Everyone notices this, even my husband, mother etc., I am not 
imagining it. Which leads to the second part of my question. When I am in 
North America, I typically shed more hair in the summer, and get a thicker 
head of hair in the winter. When I am living in Brasil, my body retains the 
same hair loss pattern, but since I am in the southern hemisphere, summer is 
winter and winter is summer. My question: Is my northern DNA dictating hair 
shedding regardless of the current climatic seasonal changes that I am living 
in? I have asked hairdressers this questions and they all agree that people do 
shed more in the summer and have more active hair follicles ( with hair in 
them! ) during the winter. Hmmmmm....these types of things keep me up at 
night. Just kidding. But I would like to know if there is any scientific 
basis/evidence/ for this. Thank you! Mayra

Re: Can hair manufacture more melanin due to sun exposure?