Sonya Baumstein began her journey Sunday from the Japanese port town of Choshi.
Her plan is to arrive in California by September as she rows across the ocean for 14 to 16 hours a day.
The 29-year-old from Orlando, Florida, embarked on a custom-made seven-metre-long, 350kg boat, taking with her 550kg of freeze-dried food, 180 high-carbohydrate drink supplements and a cache of olive oil.
“I worked three years of my life for this,” she said Sunday. “It’s 10,000 kilometres. It’s going to get bad at times. I just keep my eyes on the prize.”
Baumstein said she expects to take samples and gauge water conditions along the way to gain a better understanding of climate change.
She has refused to have a support boat trail her progress, given the environmental mission of her journey. She said the cost of a second boat would have been beyond her means and would have created additional water pollution.
Baumstein is receiving guidance from land via satellite phone and GPS, so that she can be informed on bad weather conditions at least 24 hours ahead of time. Her boat comes equipped with ballast that adjusts and allows her to take cover in a small cabin, where she can eat and sleep.
There have been 16 solo attempts across the Pacific Ocean, and only two men, one in 1991 and another in 2005, have made the journey, according to the Ocean Rowing Society.