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

Abstract

Thomas, AC, et al 2017 Seasonal trends and phenology shifts in sea surface temperature on the North American northeastern continental shelf. Elem Sci Anth, 5: 48, DOI: https://doi.org/10.1525/elementa.240 Introduction Sea surface temperatures (SST) on the North American continental shelf from Cape Hatteras to Nova Scotia (Figure 1) (hereinafter referred to as the northeastern shelf) exhibit one of the strongest warming trends of the global ocean (Burrows et al., 2011;Pershing et al., 2015; Saba et al., 2015), and the region has recently been subjected to a strong heat wave (Mills et al., 2013; Scannell et al., 2016). The warming trend has been implicated in shifts in the distribution of marine species (Lucey and Nye, 2010;Pinsky et al., 2013), many of which are of commercial importance (Nye et al., 2009;Pinsky and Fogarty, 2012), and some of which are invasive species able to exploit new ranges (e.g. Maynard et al., 2016; Stephenson et al., 2009). Such trends impose serious challenges for fisheries and fisheries management (e.g. Pinsky and Fogarty, 2012;Pershing et al., 2015). However, temperature interactions with species distributions and behaviors occur not only through trends in temperatures, latitudinal shifts in isotherms, or even in episodic events such as heat waves, but also through shifts in phenology, the timing within temperature seasonal cycles (Asch, 2015;Burrows et al., 2011). Friedland and Hare (2007) ). Winter (January-April) trends are relatively weak, and even negative in some areas; early summer (May-June) trends are positive everywhere, and later summer (July-September) trends are strongest (~1.0°C decade -1). These seasonal differences shift the phenology of many metrics of the SST cycle. The yearday on which specific temperature thresholds (8° and 12°C) are reached in spring trends earlier, most strongly over the Scotian Shelf and Gulf of Maine (~ -0.5 days year ). Three metrics defining the warmest summer period show significant trends towards earlier summer starts, later summer ends and longer summer duration over the entire study region. Trends in start and end dates are strongest (~1 day year -1 ) over the Gulf of Maine and Scotian Shelf. Trends in increased summer duration are >2.0 days year -1 in parts of the Gulf of Maine. Regression analyses show that phenology trends have regionally varying links to the North Atlantic Oscillation, to local spring and summer atmospheric pressure and air temperature and to Gulf Stream position. For effective monitoring and management of dynamically heterogeneous shelf regions, the results highlight the need to quantify spatial and seasonal differences in SST trends as well as trends in SST phenology, each of which likely has implications for the ecological functioning of the shelf.

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

“…However, for some variables, such as regional sea level pressure changes in the extratropics, internal variability can be larger than the mean climate change signal (Deser et al, 2012b(Deser et al, , 2014 The projected warming trends are generally larger in summer than in winter. The enhanced warming in summer is consistent with previous regional studies (Chollett et al, 2012;López García and Belmonte, 2011;Shaltout and Omested, 2014) and with the enhanced amplitude of the observed seasonal cycle of SSTs in the northwest Atlantic (Friedland and Hare, 2007;Thomas et al, 2017). The summertime warming is especially pronounced at high latitudes, as portions of the Arctic Ocean and adjacent seas become ice free in summer, but it is still cold enough for a thin ice layer to reform in winter, enabling SSTs to increase well above freezing in summer but not in winter.…”

“…Yet, the seasonal cycle of temperature trends has been explored in only a few studies. Warming of SSTs was more intense in summer and fall than in winter and spring off the northeast coast of the United States (Friedland and Hare, 2007; Thomas et al, 2017) and in the Caribbean (Chollett et al, 2012). In the Mediterranean, the observed warming trend was greatest in spring and lowest in winter, while the CMIP5 models project stronger warming in summer (López García and Belmonte, 2011;Shaltout and Omested, 2014).…”

Spatiotemporal variability in the phenology of the initial intra‐annual molt of American lobster (Homarus americanus Milne Edwards, 1837) and its relationship with bottom temperatures in a changing Gulf of Maine

“…Lobstermen along the Maine coast have offered that this once “predictable” phenology has become much less predictable during the years that are the focus of this study. Though anecdotal, these musings correspond with a significant increase in ocean temperature variability in the GoM that has garnered attention for the rate of warming during the last prolonged warming period (2004–2014; Chen et al., ; Pershing et al., ) and shifts in seasonal phenology (Thomas et al., ). Periods of abrupt temperature changes may provide a glimpse into future ecosystem dynamics, where extreme molting events similar to 2012 may become the new normal with increased variability in ocean temperatures in the GoM.…”

Forecasting the Seasonal Timing of Maine's Lobster Fishery

“…Providing forwardlooking information relevant to the scales at which decisions are made is a critical step, and seasonal forecasts offer one avenue toward achieving this alignment. As shifts in the timing of warming and cooling occur in marine ecosystems (Burrows et al, 2011;Thomas et al, 2017), the phenology of life events in organisms, operations and outcomes of fisheries targeting those species, and effectiveness of fishery management efforts may all be affected (Mundy and Evenson, 2011;Peer and Miller, 2014). Seasonal forecast information directed toward the phenology of important events can provide a longer planning horizon than weather forecasts and bring climate information to bear on fisheries at a time scale that is meaningful for operational and management decisions made throughout the fishing industry.…”

“…Climate change is now pushing environments beyond conditions that have come to be intuitively expected based on personal experiences. As such, shifts in the timing of seasonal events and magnitudes of extremes (Mora et al, 2013;Poloczanska et al, 2013;Thomas et al, 2017;Alexander et al, in press) can pose substantial challenges for and require adaptation of coupled ecological and social systems (Mills et al, 2013;Alexander et al, 2017).…”