185,928 research outputs found
Physical controls and mesoscale variability in the Labrador Sea spring phytoplankton bloom observed by Seaglider
No full textWe investigated the 2005 spring phytoplankton bloom in the Labrador Sea using Seaglider, an autonomous underwater vehicle equipped with hydrographic, bio-optical and oxygen sensors. The Labrador Sea blooms in distinct phases, two of which were observed by Seaglider: the north bloom and the central Labrador Sea bloom. The dominant north bloom and subsequent zooplankton growth are enabled by the advection of low-salinity water from West Greenland in the strong and eddy-rich separation of the boundary current. The glider observed high fluorescence and oxygen supersaturation within haline-stratified eddy-like features; higher fluorescence was observed at the edges than centers of the eddies. In the central Labrador Sea, the bloom occurred in thermally stratified water. Two regions with elevated subsurface chlorophyll were also observed: a 5 m thin-layer in the southwest Labrador Current, and in the Labrador shelf-break front. The thin layer observations were consistent with vertical shearing of an initially thicker chlorophyll patch. Observations at the front showed high fluorescence down to 100 m depth and aligned with the isopycnals defining the front. The high-resolution Seaglider sampling across the entire Labrador Sea provides first estimates of the scale dependence of coincident biological and physical variables
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Letter from Martin Ruiperez Sanchez to Emmett L. Bennett, Jr., March 17, 1958
No full textRuiperez Sanchez confirms receipt of Bennett's manuscript for the 1955 Pylos tablets.Classic
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Letter from Emmett L. Bennett, Jr. to Martin Ruiperez Sanchez, February 7, 1958
No full textBennett's copy of a letter he sent to Ruiperez Sanchez asking if Minos would be interested in publishing the next installment of The Pylos Tablets.Classic
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Letter from Martin Ruiperez Sanchez to Emmett L. Bennett, Jr., March 8, 1958
No full textRuiperez Sanchez confirms receipt of the plates and palace plan Bennett has sent for the publication of the 1955 Pylos tablets.Classic
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Letter from Martin Ruiperez Sanchez to Emmett L. Bennett, Jr., February 11, 1958
No full textRuiperez Sanchez responds in the affirmative to Bennett's request and goes into some details of publishing the 1955 Pylos tablets as a supplement of Minos.Classic
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Letter from Martin Ruiperez Sanchez to Emmett L. Bennett, Jr., September 15, 1958
No full textCopy of a letter to Ruiperez Sanchez in which Bennett apologizes for missing his correspondant at the colloquium in Pavia and discusses how he might obtain American support for Minos.Classic
A Laurentide outburst flooding event during the last interglacial period
No full textEpisodes of ice-sheet disintegration and meltwater release over glacial–interglacial cycles are recorded by discrete layers of detrital sediment in the Labrador Sea1, 2. The most prominent layers reflect the release of iceberg armadas associated with cold Heinrich events3, but the detrital sediment carried by glacial outburst floods from the melting Laurentide Ice Sheet is also preserved4. Here we report an extensive layer of red detrital material in the Labrador Sea that was deposited during the early last interglacial period. We trace the layer through sediment cores collected along the Labrador and Greenland margins of the Labrador Sea. Biomarker data, Ca/Sr ratios and δ18O measurements link the carbonate contained in the red layer to the Palaeozoic bedrock of the Hudson Bay. We conclude that the debris was carried to the Labrador Sea during a glacial outburst flood through the Hudson Strait, analogous to the final Lake Agassiz outburst flood about 8,400 years ago, probably around the time of a last interglacial cold event in the North Atlantic5. We suggest that outburst floods associated with the final collapse of the Laurentide Ice Sheet may have been pervasive features during the early stages of Late Quaternary interglacial periods
Neogene and quaternary planktonic foraminifer biostratigraphy and biochronology in Baffin Bay and the Labrador Sea
No full textDuring Ocean Drilling Program Leg 105, 11 holes were drilled in the Labrador Sea and Baffin Bay. Site 645 in Baffin Bay was drilled to a depth of 1147 meters below seafloor (mbsf); planktonic foraminifers were recovered in the upper 110.3 m and in a short interval between 283.8 and 293.5 mbsf. Low species diversity and the lack of species with short stratigraphic ranges inhibited establishment of a planktonic foraminifer biostratigraphic framework at Site 645. Holes 646B and 647A in the Labrador Sea were drilled to depths of 766.7 and 716.6 mbsf, respectively. Although the observed assemblages in the Labrador Sea holes were of low diversity, the first and last occurrences of several age-diagnostic species, when integrated with paleomagnetic stratigraphy, allowed the establishment of a high-latitude Miocene to Holocene planktonic foraminifer biochronology. To determine the relative timing of planktonic foraminifer datum events in the eastern North Atlantic and the Labrador Sea, this biochronology is compared with the temperate-subpolar biozonation of Weaver and Clement (1986).
The late Miocene dextral-to-sinistral coiling change in Neogloboquadrina atlantica was observed — 1.6 m.y. earlier at Site 646 than at any other site in the Atlantic. The first appearance datums (FAD) of Globorotalia margaritae, Globorotalia puncticulata, Globorotalia irtflata, and the last appearance datum (LAD) of N. atlantica are isochronous with their reported ages in the eastern North Atlantic, but the FADs of Globorotalia truncatulinoides and the modern, encrusted form of Neogloboquadrina pachyderma are diachronous
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Frances Sanchez elected state queen at the Hobbs convention (photograph)
No full textFrances Sanchez elected state queen at the Hobbs convention. (L. to R.) is Lupe M. Garcia and Joe Martinez
Seismic stratigraphy and history of deep circulation and sediment drift development in Baffin Bay and the Labrador Sea
No full textDrilling results and seismic-reflection records at and across Ocean Drilling Program (ODP) Sites 645 (western Baffin Bay), 646, and 647 (Labrador Sea) provide important constraints on the history of deep-water circulation and sedimentation in response to Cenozoic climatic change, as well as the tectonic evolution of the region. Sites 646 and 647 were drilled on the flanks of two sediment drift deposits—the Eirik Ridge and Gloria Drift, respectively. Age control at Site 645 was poor because of the restricted biotas there, but the drill site provides a continuous sequence from the lower Miocene to the present. Sediment at Site 646 was deposited at high rates, providing a high resolution record of the last 8.5 Ma. At Site 647 sedimentation was variable and discontinuous, but a complete upper-lower Eocene through lower Oligocene sequence was recovered, whereas the upper Oligocene to Holocene sequence was interrupted by several hiatuses.
The drift sequence at Site 646 was constructed after the middle to early Pliocene (ca. 4.5 Ma). Before that time, evidence exists for variable bottom-current activity, with events at about 7.5 Ma (a change in water-mass characteristics and decreasing velocities) and 5.6 Ma (an increase in current velocity preceding the major 4.5-Ma event; R2 regional reflector). The 7.5-Ma event produced a major regional reflector (R3/R4), which was originally thought to be Eocene/ Oligocene in age. A major water-mass change also occurred at the onset of ice-rafting at about 2.5 Ma in the late Pliocene. In seismic records no evidence exists of drift building before the early Pliocene, but a probable late-middle Miocene erosional event occurred on the south flank of Eirik Ridge and along the West Greenland margin. Sediment supply from the Imarssuak mid-ocean canyon (IMOC) increased concurrently with the advent of drift construction.
Gloria Drift also was built largely after the late Miocene. A major increase in sediment supply occurred in the early Pliocene, following a major hiatus (5.6 to 2.5 Ma; equivalent to the youngest possible age for the R2 reflector underlying Gloria Drift), and most seismic records exhibit sediment waves above this horizon. This increased sediment supply is the result of hemipelagic deposition from encroaching deposits of the North Atlantic mid-ocean canyon, as well as to supply of ice-rafted detritus in the late Pliocene. A hiatus encompasses the interval from approximately 17.5 to 8,2 Ma, and the interval between the two major hiatuses is extremely condensed. A deeper reflector (R3) corresponds to a change from calcareous (below) to opal-rich hemipelagic strata in the lower Oligocene, not to a regional unconformity reflecting increased bottom-water activity, as previously thought. However, some evidence exists to support a latest Eocene-earliest Oligocene increase in bottom-current activity on Gloria Drift.
In Baffin Bay, there is evidence for bottom-water activity from textural studies of cores and from apparent drift features exhibited in multichannel lines along the western margin. Probable contour-currents have been active since at least the late middle Miocene, with episodes of decreasing intensity that apparently occurred in the late Miocene and Quaternary. The record from Site 645 and in seismic lines may indicate that formation of bottom water occurred in the late Neogene in Baffin Bay in conjunction with climatic deterioration, but Baffin Bay was not an important source of deep-water masses to the Labrador Sea after the late Pliocene.
Not surprisingly, many of the Labrador Sea deep-circulation events correspond closely to major North Atlantic events and to important global climatic and paleoceanographic events, but a major drift-building episode may have occurred later in the Labrador Sea than it did in either the eastern North Atlantic or the western North Atlantic
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