Detecting and Projecting Changes in Extreme Temperature Events over Alaska

Abstract:

Through both observational and model analysis, this study investigates the likelihood of, as well as the atmospheric and oceanic conditions accompanying, two recent extreme temperature events in Alaska: a record-breaking heat wave in July 2019 and a persistent cold event in January 2012. A generalized threshold for each event was calculated and used to predict the likelihood of extreme temperature events in two climate change scenarios, using 30-member ensemble simulations by a new high resolution global climate model SPEAR, designed to investigate regional climate and extremes. Results suggest that extreme heat waves such as the July 2019 event will become increasingly more likely, from 0% before 2000 to at least 30% and 50% by 2050 in medium (SSP-245) and high (SSP-585) forcing scenarios, respectively. The likelihood of extreme cold events such as in January 2012 are shown to fall from 2% throughout the 20th century to 0% by 2050 in both medium and high anthropogenic forcing scenarios. Similar analyses are being conducted with large ensembles from other climate models to assess the robustness of the results. Extreme heat waves simulated in SPEAR are often accompanied by anomalously high upper ocean temperatures over the Gulf of Alaska during the spring and summer, which reflect “The Blob 2.0” - the anomalously warm patch of surface water observed in the Northern Pacific during the summer of 2019. This relationship could act as a predictor for future extreme heat waves. We will present analyses that seek to illustrate other large-scale oceanic and atmospheric physical properties that are related to extreme heat events. The changes in temperature extremes will pose challenges for Alaskan human health and infrastructure.