Glaciologist, working on the form and flow of glaciers and ice caps and their response to climate change, and the links between former ice sheets and the marine geological record, using a variety of satellite, airborne and shipborne geophysical tools.

He has worked, on the ice and from airborne platforms, in a number of areas of the Arctic, including Svalbard, Russian Franz Josef Land and Severnaya Zemlya, Iceland, Greenland and Baffin, Devon and Ellesmere islands in Arctic Canada. He has also undertaken many periods of work on icebreaking research vessels in the Norwegian-Greenland Sea, in the fjords and on the continental shelves of Svalbard and Greenland, and in the Weddell, Bellingshausen and Amundsen seas off Antarctica.

Julian has been awarded the Polar Medal by Her Majesty the Queen for 'outstanding contributions to glacier geophysics' and has also received the Founder's Medal (2008) and the Gill Memorial Award (1998) from the Royal Geographical Society. In 2011 he was awarded the Louis Agassiz Medal by the European Geosciences Union for 'outstanding contributions to the study of polar ice masses and to the understanding of the processes and patterns of sedimentation in glacier-influenced marine environments.' In 2014 he was awarded the IASC Medal by the International Arctic Science Committee, and in 2018 the Lyell Medal of the Geological Society of London. He has recently been elected a Fellow of the Learned Society of Wales.