Timmermans is known for her research on water masses in the Arctic, particularly how they store heat and freshwater, and move throughout the region. She uses instruments placed in the ocean for extended periods of time to investigate water masses deep in the Canada Basin. The challenges associated with the long-term placement of instruments in the ocean were described in a 2004 article at National Geographic. The resulting data allow her to track the movement of water from the Pacific Ocean into the Arctic Ocean, and has implications for changes in the density layers of the Arctic Ocean and the amount of oxygen stored underneath sea ice. Timmermans' research has found that water in the region is becoming "spicier" which is a change in the balance of how temperature and salinity impacts density. This change means temperature will become more important in determining the density of water masses in the region. Her research has also determined that the amount of heat stored in the Arctic has doubled over the last 30 years which will slow the rate new sea ice is formed in the region. This research was widely covered in the press because the added heat in the region will trigger additional melting of sea ice. These changes in the water temperature are also changing how the Arctic Ocean carries sound, and changing the movement of water in the Arctic Ocean.