The kinematic and hydrographic structure of the Gulf of Maine Coastal Current

Pettigrew, Neal R.; Churchill, James H.; Janzen, C.; Mangum, L. J.; Signell, Richard P.; Thomas, Andrew C.; Townsend, David W.; Wallinga, John; Xue, Huijie

doi:10.1016/j.dsr2.2005.06.033

Cited by 170 publications

(195 citation statements)

References 22 publications

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“…L diff is driven by the variability in the currents experienced by larvae spawned at different times or entrained into different coastal eddies (9,14); it could also include the effects of other larval transport mechanisms, such as shipping or fisheries. There is strong weather system-driven (23,24) and interannual variability (25,26) in the coastal current; its SD is comparable to the mean, suggesting that the upper limit on the stochastic component of larval transport should be the magnitude of the mean larval transport L adv (14). Despite these expectations, the variability in larval transport diagnosed by the model from the evolution of the cline is w3.5 times greater than the mean larval transport.…”

Section: Discussion Of the Carcinus Systemmentioning

confidence: 56%

Asymmetric dispersal allows an upstream region to control population structure throughout a species’ range

Pringle

Blakeslee

Byers

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

100

126

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In a single well-mixed population, equally abundant neutral alleles are equally likely to persist. However, in spatially complex populations structured by an asymmetric dispersal mechanism, such as a coastal population where larvae are predominantly moved downstream by currents, the eventual frequency of neutral haplotypes will depend on their initial spatial location. In our study of the progression of two spatially separate, genetically distinct introductions of the European green crab (Carcinus maenas) along the coast of eastern North America, we captured this process in action. We documented the shift of the genetic cline in this species over 8 y, and here we detail how the upstream haplotypes are beginning to dominate the system. This quantification of an evolving genetic boundary in a coastal system demonstrates that novel genetic alleles or haplotypes that arise or are introduced into upstream retention zones (regions whose export of larvae is not balanced by import from elsewhere) will increase in frequency in the entire system. This phenomenon should be widespread when there is asymmetrical dispersal, in the oceans or on land, suggesting that the upstream edge of a species' range can influence genetic diversity throughout its distribution. Efforts to protect the upstream edge of an asymmetrically dispersing species' range are vital to conserving genetic diversity in the species.invasive species | marine genetics | phylogeography | physical oceanography N ovel genetic material can appear in a population through mutation, migration, or long-distance dispersal events which may be human-mediated. In a single well-mixed population, the evolution of the frequency of novel neutral alleles will be governed by random genetic drift, not their initial spatial distribution (1). However, spatial structure and complexity can alter this expectation. In a metapopulation linked by migration, alleles introduced into source populations are more likely to persist than those that are introduced into sinks (2-4). Many metapopulations are embedded in complex spatial systems with a preferential direction of migration ("asymmetric dispersal"). In these systems, little is known about the equilibrium frequency of novel alleles or how this frequency depends on the location where these new lineages appear.Asymmetric dispersal is common where propagules are carried long distances by wind or water. In atmospheric, riverine, and oceanic flows, there is usually a predominant flow direction (downstream or downwind) that biases dispersal, and eddies or weather systems that slow or reverse such flow add a stochastic (and potentially upstream) component of migration. For example, many terrestrial plant species have propagules that can be dispersed by the winds (5), and a recent study of the spatial patterns of diversity in moss, liverwort, and lichen flora in the Southern Hemisphere were found to be best explained by the predominantly downwind dispersal (6). Further evidence that asymmetric dispersal can structure a species' genetic patter...

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Section: Discussion Of the Carcinus Systemmentioning

confidence: 56%

Asymmetric dispersal allows an upstream region to control population structure throughout a species’ range

Pringle

Blakeslee

Byers

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

100

126

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“…These data show substantially colder and fresher surface and deep waters in the mid 1960s than later years, and echo the changes observed at the same time in nearby Emerald Basin on the Scotian Shelf (Petrie and Drinkwater, 1993). Surface waters over Jordan Basin circulate cyclonically, and are cool and fresh, reflecting their Arctic source (Pettigrew et al 2005) with additional contributions from local rivers and especially the Gulf of St. Lawrence (Houghton and Fairbanks, 2001). The strength of these surface flows, especially the Nova Scotia Current and the Eastern Maine Coastal Current, should affect upwelling in Jordan Basin as they define the Jordan Basin Gyre (Figure 1).…”

Section: Introductionsupporting

confidence: 48%

Sediment flux and recent paleoclimate in JordanBasin, Gulf of Maine

Keigwin

Pilskaln

2015

Continental Shelf Research

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We report planktonic foraminiferal fluxes (accumulation rates) and oxygen isotopes (δ 18 O) from a nine-month sediment trap deployment, and δ 18 O from three sediment cores in Jordan Basin, Gulf of Maine. The sediment trap was deployed at 150 m, about halfway to the basin floor, and samples were collected every three weeks between August 2010 and May 2011. The planktonic foraminiferal fauna in the trap is dominated by Neogloboquadrina incompta that reached a maximum flux in the second half of October. Oxygen isotope ratios on that species indicate that on average during the collecting period it lived in the surface mixed layer, when compared to predicted values based on data from a nearby hydrographic buoy from the same period. New large diameter piston cores from Jordan Basin are 25 and 28 m long. Marine hemipelagic sediments are 25 m thick, and the sharp contact with underlying red deglacial sediments is bracketed by two radiocarbon dates on bivalves that indicate ice-free conditions began 16,900 calibrated years ago. Radiocarbon dating of foraminifera indicates that the basin floor sediments (270-290 m) accumulated at >3 m/kyr during the Holocene, whereas rates were about one tenth that on the basin slope (230 m). In principle, Jordan Basin sediments have the potential to provide time series with interannual resolution. Our results indicate the Holocene is marked by ~2°C variability in SST, and the coldest events of the 20th century, during the mid 1960s and mid 1920s, appear to be recorded in the uppermost 50 cm of the seafloor.

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“…The data show slower warming rates in localized regions over the strongly tidally mixed shallow bathymetry of Georges Bank, Nantucket Shoals and the southwestern shore of Nova Scotia. Increased vertical mixing, however, cannot be the only mechanism suppressing warming rates, as the strongly mixed Eastern Maine Coastal Current and mouth of the Bay of Fundy (Pettigrew et al, 2005) exhibit strong positive trends that are only slightly less than those over the stratified deeper Gulf of Maine basins and the Scotian Shelf. Over much of the MAB, shelf SST trends have a cross-shelf gradient, strongest on the outer shelf in closest proximity to the Gulf Stream, weakest near shore where shallower depths likely enable more rapid water column cooling and episodic summer wind-driven upwelling events (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…The data provide spatial detail within the Gulf of Maine that also has similarities to known hydrographic processes. The summer start trend is strongest over the deeper basins, and relatively weak over the strongly advective and tidally mixed Eastern Maine Coastal Current and southern tip of Nova Scotia (Pettigrew et al, 2005;Townsend et al, 2006). The progressively later summer end date is strongest in the Gulf of Maine, over Georges Bank and on the Scotian Shelf, but weaker over MAB, where it is weakest nearshore.…”

Section: Discussionmentioning

confidence: 99%

“…Residual circulation and water mass analysis show that shelf water as far south as Cape Hatteras is linked to equatorward flow of subarctic water masses along and on the North American shelf (Loder et al, 1998;Townsend et al, 2006). Water of higher latitude origin flows south along the Scotian Shelf, circulates cyclonically around the deeper basins of the Gulf of Maine, and then anti-cyclonically around Georges Bank before flowing south into the Mid-Atlantic Bight (MAB) (Mountain, 2003;Pettigrew et al, 2005;Townsend et al, 2006). The canonical view, based on observed phase-lagged temperature anomaly signals at latitudinally separated buoy locations along the shelf, is that major changes in SST and hydrographic structure over the shelf are predominantly driven by advection of anomalous properties from higher latitudes upstream (Loder et al, 2001;Shearman and Lentz, 2010).…”

Section: Research Articlementioning

confidence: 99%

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

Thomas

Pershing

Friedland

et al. 2017

Elementa: Science of the Anthropocene

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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.

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The kinematic and hydrographic structure of the Gulf of Maine Coastal Current

Cited by 170 publications

References 22 publications

Asymmetric dispersal allows an upstream region to control population structure throughout a species’ range

Asymmetric dispersal allows an upstream region to control population structure throughout a species’ range

Sediment flux and recent paleoclimate in JordanBasin, Gulf of Maine

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

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