This is probably one of the hardest updates I've ever had to write. Today, I've made the decision to abort the Cycle South expedition - at least the rest of the southerly journey to the pole. Instead, I am heading back to my starting point, Hercules Inlet.

I had been making steady progress south for the past eight days and travel has been difficult but not impossible. That said, my actual mileage was much different than my anticipated mileage. Even though I had the good fortune of being able to follow an old drifted in cat trail, I still wasn't making the progress I had hoped. Again, all not terrible.

However, as I started to calculate my mileage south of 85 degrees, I realized that due to an increased amount of climbing, headwinds, and consequently sastrugi and drifts, my daily mileage would realistically be closer to 10 nautical miles per day. At that rate, my chances of making the pole before my food ran out (as well as the end of the season) would be zero - odds that would basically mean a costly extraction by ALE somewhere before the pole.

Now I've taken a lot of chances in all kinds of shapes and forms but this was not a chance I was willing to take. I cried in my tent for a long time when I finally decided.

I made one last attempt at biking south before crashing in the soft snow, I yelled and screamed and punched my fist in the snow. I was exasperated. Then, I got up and looked around. The wind had picked up substantially, but all around there was just snow. Just like always. Antarctica. I laughed to myself. This was not the first time that this icy place has turned back an expedition.

After a few minutes, I turned my back to the wind and started the long ride back to Hercules Inlet. After an hour of steady progress, I got a flat in my rear tire and had to set up my tent to change it.

But at least I CAN turn around. My dad and all the other people suffering with Parkinson's Disease have no other choice but to continue forward day after day, year after year. Understanding this simple fact seemed to put my whole expedition into perspective as well as the real goal of this trip: to help raise awareness for the groundbreaking research that is being done by the Davis Phinney Foundation and their efforts to use bicycles to help improve the lives of those who live with Parkinson's. Please donate here: www.davisphinneyfoundation.org/giving/donate/

Of course, you can also check out the 'get involved' section of my web site to learn more about how you can use bicycles to help change the world.

It's hard to think of all my sponsors and supporters that I'm letting down. Most have taken a big gamble in backing this adventure. I sent an InReach message to the team at Ergodyne. Their gear is some of the best I've ever used, and their motto, tenacious, has become a mantra for me in every aspect of my life. I only hope in the upcoming weeks and months I can live up to their high standards. I don't say this lightly: amazing people and amazing company. Chip from DeLorme sent an inReach message as well. I very much appreciated the kind words.

Image: Antarctic bike shop. Changing a tube with a bad valve.