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Elisabeth M. Brouwers

Publications and source records attributed to Elisabeth M. Brouwers.

8 recordsLinked to original sources
USGS2015

An Arctic and Subarctic ostracode database: Biogeographic and paleoceanographic applications

A new Arctic Ostracode Database-2015 (AOD-2015) provides census data for 96 species of benthic marine Ostracoda from 1340 modern surface sediments from the Arctic Ocean and subarctic seas. Ostracoda is a meiofaunal, Crustacea group that secretes a bivalved calcareous (CaCO 3 ) shell commonly preserved in sediments. Arctic and subarctic ostracode species have ecological limits controlled by temperature, salinity, oxygen, sea ice, food, and other habitat-related factors. Unique species ecology, shell chemistry (Mg/Ca ratios, stable isotopes), and limited stratigraphic ranges make them a useful tool for paleoceanographic reconstructions and biostratigraphy. The database, described here, will facilitate the investigation of modern ostracode biogeography, regional community structure, and ecology. These data, when compared to downcore faunal data from sediment cores, will provide a better understanding of how the Arctic has been affected by climatic and oceanographic change during the Quaternary. Images of all species and biogeographic distribution maps for selected species are presented, with brief discussion of representative species’ biogeographic and ecological significance. Publication of AOD-2015 is open-sourced and will be available online at several public websites with latitude, longitude, water depth, and bottom water temperature for most samples. It includes material from Arctic abyssal plains and submarine ridges, continental slopes, and shelves of the Kara, Laptev, East Siberian, Chukchi, Beaufort Seas, and several subarctic regions.

Hydrobiologia↗
USGS2010

Microfaunal evidence for elevated Pliocene temperatures in the Arctic Ocean

The migration of thermophilic marine Ostracoda into the Arctic Ocean during the Pliocene indicates that winter and summer ocean temperatures around Arctic margins were ≥ 0 °C and > 3 °C, respectively, and that ice-free conditions existed for most or all of the Arctic. By at least 3.5–3.0 Ma, probably earlier, the opening of the Bering Strait allowed marine organisms to migrate through the Arctic Ocean, mostly from the Pacific Ocean. Migrant taxa such as Cythere, Hemicythere, and Neomonoceratina are known from Pliocene deposits of Alaska and Canada as well as Neogene deposits of the North Pacific and Atlantic oceans. On the basis of ecological and Zoogeographic information on ostracode species from more than 800 modern “core top” samples for the North Atlantic, North Pacific, and Arctic Oceans, we determined winter and summer temperature tolerances for migrant taxa to be at or above about 0 °C and 3 °C. This suggests ice-free summers, and probably, a perennially ice-free Arctic Ocean in some regions. Elevated water temperatures in the Arctic Ocean between 3.5 and 2.0 Ma is supported by evidence for late Pliocene increased meridional heat transport in the North Atlantic Ocean.

Paleoceanography and Paleoclimatology↗
USGS1994

Late Pliocene paleoeco­logic reconstructions based on ostracode assemblages from the Sagavanirktok and Gubik formations, Alaskan North Slope

Shallow-marine ostracode assemblages from upper Pliocene sediments of the upper part of the Sagavanirktok Formation and lower part of the Gubik Formation record the last warm period that occurred before the onset of significant cooling of the Arctic Ocean and the initiation of Northern Hemisphere continental glaciation. The informally named Colvillian and Bigbendian transgressions represent the oldest deposits of the Gubik Formation and are dated, based on various lines of evidence, between 2.48 and 3 Ma. Ostracode faunas from the lower part of the Gubik Formation indicate a cold-temperate to subfrigid marine climate with summer bottom temperatures 1-4 C warmer than today. Deposits of the upper part of the Sagavanirktok Formation at Manning Point and Barter Island are older than Colvillian sediments but are believed to be late Pliocene in age and contain an ostracode fauna that has many species in common with the lower part of the Gubik Formation. The Sagavanirktok ostracode faunas indicate a cold-temperature to subfrigid marine climate, similar to that inferred for the lower part of the Gubik Formation, with summer bottom temperatures 1-3 C warmer than today. The opening of Bering Strait at about 3 Ma altered Arctic Ocean assemblage composition as Pacific species migrated into the Arctic and North Atlantic oceans. The admixture of evolutionarily distinct faunas from the Atlantic and Pacific oceans identifies Colvillian (and younger) faunas and provides a convenient reference horizon in the Alaskan fossil record. The marine climatic deterioration that followed the Bigbendian appears to have been abrupt and is documented by biotic turnover, with large numbers of species extinctions and first appearances of new species. The change in species composition can be attributed to the cooling of the Arctic Ocean during the late Pliocene.

Alaska↗
USGS1993

Sediment export by ice rafting from a coastal Polynya, Arctic Alaska, U.S.A.

Strong offshore winds in early 1989 produced a shore polynya that reached along the entire north coast of Alaska and eastward beyond the mouth of the Mackenzie River in Canada. From January through April, this open water periodically exposed the shelf to sediment entrainment by suspension freezing. This process requires turbulence and supercooled water, which results in the formation of frazil and anchor ice. The resulting granular, sediment-laden ice was observed to extend over 100 km seaward of the outer continental shelf after having been advected offshore. It was sampled to determine sediment type and to quantify the particle load. The particle size was mainly silt and clay, with local admixtures of as much as 27% sand and coarser clasts. Melted ice samples contained from 31 to nearly 600 mg L -1 of sediment. Combining these data with over 400 km of shipboard and aerial observations, photographs, and computer analysis of a summer Landsat image, we estimated the sediment load per unit area of sea ice. Seaward of the shelf, in regions of dense pack ice, a conservatively estimated sediment load was over 289 t km -2 . Using a westward summer drift rate of 3 cm s -1 , the sediment transport through a 1-km-long north-south segment is 67,418 t during 3 mo. In terms of regional sediment dynamics (littoral transport estimated at 10,000 t during the same period) and sediment budget (continental denudation estimated at 10 t km -2 during the same period), this number is very significant. Benthic microfossils indicate that bottom sediment incorporated in the ice came from water depths ranging from the inner neritic seaward to 50 m. The large load of shelf-derived sediment observed seaward of the continental shelf indicates that ice entrainment and transport cause shelf erosion. Nothing is known about sediment release over the Arctic Ocean Basin from these pulses of dirty ice that are periodically introduced into the Transpolar Drift.

Alaska↗