Diagnosing the warming of the Northeastern U.S. Coastal Ocean in 2012: A linkage between the atmospheric jet stream variability and ocean response

Abstract

The temperature in the coastal ocean off the northeastern U.S. during the first half of 2012 was anomalously warm, and this resulted in major impacts on the marine ecosystem and commercial fisheries. Understanding the spatiotemporal characteristics of the warming and its underlying dynamical processes is important for improving ecosystem management. Here, we show that the warming in the first half of 2012 was systematic from the Gulf of Maine to Cape Hatteras. Moreover, the warm anomalies extended through the water column, and the local temperature change of shelf water in the Middle Atlantic Bight was largely balanced by the atmospheric heat flux. The anomalous atmospheric jet stream position induced smaller heat loss from the ocean and caused a much slower cooling rate in late autumn and early winter of 2011–2012. Strong jet stream intraseasonal oscillations in the first half of 2012 systematically increased the warm anomalies over the continental shelf. Despite the importance of advection in prior northeastern U.S. continental shelf interannual temperature anomalies, our analyses show that much of the 2012 warming event was attributed to local warming from the atmosphere.

Seasonal trends and phenology shifts in sea surface temperature on the North American northeastern continental shelf

“…Local atmospheric conditions that control wind and heat flux can play a role in hydrographic, SST and ecological variability of the shelf (e.g. Pershing et al, 2012;Li et al, 2014;Chen et al, 2014). Our results suggest that atmospheric conditions over the region in spring and summer are also related to changes in SST phenology, especially on the Scotian Shelf and Gulf of Maine.…”

“…The extent to which this weakening is due to heat flux, water column mixed layer depth changes and/or advective forcing processes acting during fall or due to the increased water column heat left over from the strongly warming summer is best addressed with future model studies. Chen et al (2015Chen et al ( , 2014 suggest that, at least for the extreme warming event of 2012, changes in atmospherically-driven heat flux that began the previous fall and extended into winter and spring drove warm anomalies the following spring-summer. An important factor that could influence a seasonal bias in SST trends is mixed layer depth.…”

“…Galbraith et al (2012) show that the trends in SST in spring-summer-fall over the Gulf of St. Lawrence, immediately to the north of our study area, have a strong correlation to changes in local surface air temperature. Recent work by Chen et al (2014Chen et al ( , 2015 shows that the extreme 2012 SST anomalies over the entire study area were not phase-lagged, and their model simulations suggest that the synchronous anomalies were driven by anomalous heat flux linked to changes in atmospheric patterns that began the preceding fall. They show that fall-winter advective processes work against these heat flux anomalies to cool the water column, but that air-sea heat flux associated with shifts in jet stream position in both fall and winter-spring overwhelmed the advective processes and resulted in an anomalously warmer water column leading to the strong 2012 SST anomalies.…”

Frequency of marine heatwaves in the North Atlantic and North Pacific since 1950

“…These events have been referred to as marine heatwaves and have been described as regions of large-scale and persistent positive sea surface temperature (SST) anomalies [Pearce et al, 2011]. Well-known marine heatwaves have occurred in the Mediterranean Sea [Black et al, 2004;Olita et al, 2007], off Western Australia [Pearce and Feng, 2013], in the northwest Atlantic [Mills et al, 2013;Chen et al, 2014Chen et al, , 2015, and in the northeast Pacific [Bond et al, 2015;Hartmann, 2015]. Like heatwaves on land, marine heatwaves are likely to become more frequent and intense under continued anthropogenic warming assuming fixed temperature thresholds [Solomon et al, 2007].…”

Projected sea surface temperatures over the 21st century: Changes in the mean, variability and extremes for large marine ecosystem regions of Northern Oceans

“…Extreme conditions, however, also occur in the world oceans (Hobday et al, 2016) and there is a growing appreciation that extremes strongly influence population dynamics and biogeography of many organisms (Portner et al, 2001;Lynch et al, 2014). Recent studies have explored periods with very warm SSTs or "ocean heat waves" in the northwest Atlantic (Mills et al, 2013;Chen et al, 2014Chen et al, , 2015, Northern Hemisphere oceans (Scannell et al, 2016), Mediterranean Sea (Black et al, 2004;Olita et al, 2007), off the coast of western Australia (Pearce and Feng, 2013;Wernberg et al, 2013), and over global coastal regions (Lima and Wethey, 2012). Significant negative effects on living marine resources and marine ecosystems were observed during some of these extreme periods (Mills et al, 2013;Wernberg et al, 2013;Pershing et al, 2015;Caputi et al, 2016).…”