Last December, the two teens were among 20 secondary students who visited the South Pole. This September, they went to the North Pole with 20 other students.
Both trips were funded by local charity organisation Yan Oi Tong (YOT) and co-organised by YOT and Hong Kong Discovery magazine. The trips boosted the pair's commitment to the environment.
"When I came back from the South Pole, I wanted to take more responsibility in protecting the environment," says 18-year-old Clara, who studies at Canadian International School.
"Going on a second trip is like telling myself and others that if I'm determined, I can do anything."
Adds Jack: "One of our roles was to take care of students who were new to the trip. After going to both poles, we could share our experience with other students."
Jack is also 18 and a student at Christian and Missionary Alliance Sun Kei Secondary School.
Despite the similarity in their climates, the South and the North Poles differ markedly in some ways.
"The South Pole is situated on the continent of Antarctica and is surrounded by oceans and thick ice sheets. The extreme temperature makes it uninhabitable," says Professor Chan Lung-sang of the Department of Earth Sciences at the University of Hong Kong.
"The Arctic region is a frozen ocean surrounded by land covered mainly by short shrubs, mosses and algae. The warm Atlantic current makes it less cold. The land within the Arctic circle is inhabited by the Inuit people."
Chan, who travelled with the students on both trips, says the recent rise in global temperatures is more apparent in the Arctic region.
While both trips were inspiring, both Clara and Jack preferred their North Pole visit. "On our very first Zodiac boat trip, we saw a polar bear in the distance. It was the top thing on my wish list. I had very mixed feelings. I knew it was endangered and so rare to see," Clara says.
Jack found his own moment of bliss when he saw the northern lights for the first time.
"It was surreal. The lights looked like a gigantic flowing sheet of green curtains. They came and went and surrounded me, 360 degrees," he says.
Meeting young indigenous Inuit people gave the students a lesson in globalisation.
"I was surprised to see that they had iPhones and Facebook accounts. They wanted to add us right away," Jack says.
"And they were wearing fashionable T-shirts, baggy trousers and sports shoes they bought online. They actually looked cooler than us," Clara adds.
But there were some obvious differences between teens there and in Hong Kong.
"When their family needs them to work or hunt, students will just skip school that day. I think it's a part of their culture and we need to respect that," says Jack.
Both students have been touched by their trips. "When I was gazing at the night sky above me and listening to the silence out there, my mind was occupied with nothing but nature," Clara says. "It gave me a deeper understanding of the world, the environment and myself."
Jack plans to study environmental policy at university and pursue a career in the field afterwards. "Humans want to conquer the world and take its resources, but on this trip, I learned how [insignificant] we are in the face of nature," he says.
"We have to pay attention to our environment."