Thaw
Primary reference(s)
WMO, 1992. International Meteorological Vocabulary, WMO-No. 182. World Meteorological Organization (WMO). Accessed 13 October 2020.
Additional scientific description
Additional definitions of thaw include:
To melt a substance, ice for example, by warming it to a temperature greater than the melting point of the substance, or to have frozen contents melted (AMS, 2012).
To free something from the binding action of ice by warming it to a temperature above the melting point of ice (AMS, 2012).
A warm spell when ice and snow melt, for example, ‘January thaw’ (AMS, 2012).
Metrics and numeric limits
Not applicable.
Key relevant UN convention / multilateral treaty
Not applicable.
Examples of drivers, outcomes and risk management
A spring thaw is when warmer temperatures and resulting snow melt can produce large amounts of runoff in a short period of time, as each cubic foot of compacted snow contains gallons of water. During early spring, frozen land prevents melting snow or rainfall from seeping into the ground. The water then runs off the surface and flows into lakes, streams, and rivers, causing excess water to spill over their banks. The addition of seasonal storms can result in severe spring flooding (US FEMA, no date).
The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning to infectious diseases and mental health problems (acute and long-term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013).
Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants thereby increasing the risk of water-borne diseases but may also affect proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of the following communicable diseases: water-borne diseases (such as typhoid fever, cholera, leptospirosis and hepatitis A) and vector-borne diseases (such as malaria, dengue and dengue haemorrhagic fever, yellow fever, and West Nile Fever) (WHO no date).
The longer-term health effects associated with a flood are less easily identified. They include effects due to displacement, destruction of homes, delayed recovery and water shortages (WHO, 2013).
References
AMS, 2012. Glossary of Meteorology: Thaw. American Meteorological Society (AMS). Accessed 26 November 2019.
US FEMA, no date. Spring Flooding: Risks and Protection. US Federal Emergency Management Agency (FEMA). Accessed 13 October 2020.
WHO, no date. Flooding and communicable diseases fact sheet. World Health Organization (WHO). Accessed 4 October 2020.
WHO, 2013. Floods in the WHO European Region: Health effects and their prevention. World Health Organization (WHO), Regional Office for Europe. Accessed 2 October 2020.