Born in Christchurch, New Zealand, Merton was educated at Christ's College, and continued his art studies at the Canterbury College School of Art, working between London, England and New Zealand from 1905-10.  During European visits, he spent extensive time in the Netherlands, Cornwall and Brittany. He attended sketching lessons taught by Frances Hodgkins in Concarneau, and while in France between 1910-13, he studied at the Academie Colarossi, and also with P Tudor-Hart.

Merton married the American artist Ruth Calvert Jenkins in 1914, and they had two sons (one born in France, the other in New York) before his wife died in 1921.  He then travelled in France, and based himself again in England, where he later died after a long illness. His titles include St Ives, Barnoon Hill; St Ives and St Michael's Mount (all dated 1910).