Rogue waves are extreme waves with overall or crest heights that are abnormally high relative to the background significant wave height (WMO, 2018).

Seawater intrusion is the process by which saltwater infiltrates a coastal aquifer, leading to contamination of fresh groundwater (NRC, 2011).

Sea ice is any form of ice found at sea (WMO, 2015).

Ice flow is the motion of ice driven by gravitational forces, ice stress or, for sea ice, wind, water currents and tide (AMS, 2012).

Seiches are sea-level oscillations at the resonant frequency of enclosed bodies of water (WMO, 2011).

A storm surge reflects the difference between the actual water level under the influence of a meteorological disturbance (storm tide) and the level which would have occurred in the absence of the meteorological disturbance (i.e., astronomical tide) (WMO, 2008, 2011, 2017).

A storm tides is the actual sea level as influenced by a weather disturbance. The storm tide consists of the normal astronomical tide plus the storm surge (WMO, 2017).

Tsunami is the Japanese term meaning wave (‘nami’) in a harbour (‘tsu’). It is a series of travelling waves of extremely long length and period, usually generated by disturbances associated with earthquakes occurring below or near the ocean floor (IOC, 2019).

Ocean acidification refers to a reduction in the pH of the ocean over an extended period, which is caused primarily by uptake of carbon dioxide from the atmosphere and can also be caused by other chemical additions or subtractions from the ocean (IPCC, 2011).