The owner of the clothes has not yet been identified but the family of Ms Pope have been informed of the find.
The discovery was made at 10.28am on Thursday morning by a member of the public, in an area of open land north of the coastal path near Dancing Ledge, near Swanage.
Senior investigating officer Neil Devoto, of Dorset Police's Major Crime Investigation Team, said: “Following the discovery of these items of clothing, a full and thorough search will now take place in the field and surrounding area.
“We have seized the clothing and investigations will now be carried out to identify who they belong to.
“We have updated Gaia’s family who continue to be supported by specially-trained officers.
“Our thoughts remain with them at this very difficult time.”
Ms Pope was staying at an address in Swanage, Dorset, when she disappeared on 7 November.
Less than an hour before her last confirmed sighting at 3.39pm, she was being driven between Langton Matravers and Swanage by a family member when they stopped off for fuel at St Michael's Garage on Valley Road in Swanage.
Police have released two CCTV images of the 19-year-old inside the garage buying an ice cream at around 2.55pm.
The last confirmed sighting of Gaia was at an address in Manor Gardens on Morrison Road in Swanage.
She was wearing grey and white woven leggings, a red checked shirt and white trainers.
Detectives arrested a 71-year-old woman and 19-year-old man this week over the disappearance of Ms Pope. Both were released under investigation.
Police said they were both known to Ms Pope.
Police have urged members of the public to come forward if they have any information.
“I am also urging anyone who has seen any suspicious activity in the area of Morrison Road and Priests Way since Tuesday 7 November to please contact us,” Mr Devoto said.
