Connections between north‐central United States summer hydroclimatology and Arctic sea ice variability

Abstract

Arctic sea ice has been shrinking at unprecedented rates over the past three decades. These cryospheric changes have coincided with greater incidence of global extreme weather conditions, including increased severity and frequency of summer heatwaves and extreme rainfall events. Recent studies identify potential physical mechanisms related to Rossby wave and resonance theories that may attribute the observed changes in extreme summer weather patterns to Arctic sea ice decline. This study explores the linkages between summer Arctic sea ice variability and hydroclimate of the north‐central United States (US) during the 1979 to 2013 period. Since 1979, summers with low sea ice conditions have coincided with significant increases in mean, minimum, maximum, and dew point air temperatures. Also apparent are increases in seasonal precipitation, the number of wet days, heavy (>95th percentile) precipitation days, and accumulated precipitation over the region. These moisture changes coincide with atmospheric patterns typically observed during anomalously wet summers, known to prompt flooding across the Upper Mississippi River Valley (UMRV) region. Low sea ice summers have coincided with (1) enhanced southerly air flow and increased activity of the Great Plains Low Level Jet (GPLLJ) over the study area, (2) increased occurrence of moist tropical air masses over the UMRV region, and (3) amplified 500 hPa flow over the Pacific‐North American region with a ridge situated over the central‐eastern portions of the North American continent emanating from Greenland and the central Arctic basin. The results suggest summer Arctic sea ice variability has been associated with recent hydroclimate anomalies of the north‐central United States and the UMRV region and add to our growing knowledge of the connections between a changing Arctic environment and concurrent mid‐latitude climate variability.

Spatio-Temporal Linkages between Declining Arctic Sea-Ice Extent and Increasing Wildfire Activity in the Western United States

“…Our understanding of the processes is constantly evolving (e.g., [13,14]) with recent research suggesting that, among others, ASIE is potentially a controlling factor or interacts with (1) the Atlantic multidecadal oscillation (AMO; [14]); (2) the NAO [13,15]; (3) the western Pacific pattern (WP) and El Nino Southern Oscillation (ENSO; [15]); (4) declining summertime total kinetic energy and zonal flow [16]; (5) the Pacific Decadal Oscillation (PDO; [17]); (6) surface temperature extremes [10]; and (7) surface precipitation extremes [18,19]. An example of the evolution of our understanding of the linkages includes studies [13,20], which found that contrary to earlier work based on empirical data [2,5], model simulations show that lower levels of ASIE are associated with reductions in wintertime cold events in Northern Europe, not increases in these events.…”

Greenland blocking index daily series 1851–2015: Analysis of changes in extremes and links with North Atlantic and UK climate variability and change

“…However, more generally our results indicate that high GBI winter anomalies are co-located with sea-ice anomalies, while there seems to be minimal influence of sea-ice anomalies on the recent significant increase in summer GBI. Greenland high-pressure blocking is a key measure of changes in North Atlantic and Northern Hemisphere atmospheric circulation and potential Arctic-mid-latitude climate linkages (e.g., Woollings et al, 2008;Davini et al, 2012a;Hall et al, 2015;Hanna et al, 2015;2016;Mattingly et al, 2015;2016;McLeod and Mote, 2016;Budikova et al, 2017;Ballinger et al, 2018). Blocking is generally used to describe a large, quasistationary mid-latitude anticyclone that persists for at least a few days and is associated with increased large-scale meridional flow (Rex, 1950), but there is no clear consensus on an exact definition (e.g., Woollings et al, 2008).…”

United States Heat Wave Frequency and Arctic Ocean Marginal Sea Ice Variability

“…These modifications suggest the presence of ridge‐trough‐ridge pattern of atmospheric circulation and a stationary wave train. Such features have been documented as responses to declining sea ice in various areas of the Arctic including HB and Labrador Sea (Budikova et al, ; Vihma, ). The resultant atmospheric flow would bring consistent streams of warm air from the desert southwest into the study area and increase the potential for heat waves to form throughout the summer season.…”

“…Rossby wave and resonance theories have been used to argue that Arctic sea ice decline and Arctic warming can lead to NH atmospheric flow modifications with a potential for increased persistence and blocking events in the middle latitudes via a weakening of the poleward thermal gradient, mean zonal winds and thermal winds, reduction in total atmospheric kinetic energy, and an increase in the amplification of quasistationary wave numbers 6–8 (Coumou et al, , ; Francis & Vavrus, , ; Tang et al, ). These alterations provide more conducive environments for the development of summertime extreme weather events across the NH midlatitudes (Budikova & Chechi, ; Budikova et al, ; Coumou et al, ; Screen et al, ). In recent decades, low summer sea ice has been associated with the negative phase of the North Atlantic Oscillation (NAO) with increased (decreased) upper‐level geopotential heights (zonal wind speeds) across the polar cap and a northward shift in the subpolar jet stream, leading to increased ridging and southerly advection of warm air from the subtropics (Budikova & Chechi, ; Francis & Vavrus, ; Mann et al, ; Schubert et al, ).…”

“…Arctic warming is partially attributable to sea ice decline with two‐way effects on ridge‐trough jet stream patterns that may influence middle latitude weather, including the incidence of extreme weather events (e.g., Budikova et al, ; Ding et al, ; Francis, ; Tang et al, ). Coincidence of dramatic SIE reductions with increased incidence of extreme summer temperatures in the midlatitudes over the last three to four decades may suggest potential physical mechanisms connecting the two and warrant an investigation of the relationships and dynamic linkages between the frequency of midlatitude extreme heat events and Arctic sea ice variability during the boreal summer (June–August).…”