On the export of dense water from the Weddell and Ross Seas

We describe the seasonal and interannual variability of volume transports in Weddell and Ross Seas using the 1/12deg; 20-yr simulation of the OCCAM global ocean general circulation model. The average simulated full-depth cumulative 28.5 plusmn; 2.9 Sv (1 Sv equiv; 106 m3 s-1) and 13.4 plusmn; 5.2 Sv, across the main export regions of the Weddell and Ross Seas, respectively. The values of mean outflow of Antarctic Bottom Water (AABW) (defined by neutral density gamma;n 28.27 kg m-3) from the Weddell and Ross Seas of 10.6 plusmn; 3.1 Sv and 0.5 plusmn; 0.7 Sv, respectively, agree with the range reported in historical observational studies. Variability in AABW export is predominantly at periods of ~1 yr and 2-4 yr. The transit time taken by AABW sourced in the Southern Weddell Sea to reach the main Weddell export zone is ~2 yr. Lagged correlation between the thermohaline properties of AABW source waters and AABW export indicates that recent shelf waters freshening trends are likely related to changes in the AABW outflow rates

The Flow of Dense Water Plumes in the Western Weddell Sea Simulated with the Finite Element Ocean Model (FEOM)

Ocean simulations performed with the Finite Element Ocean Model (FEOM) were used to show the relevance of the location of the dense water plume source on the western Weddell Sea continental shelf. When the plume starts close to the tip of the Antarctic Peninsula it flows into Bransfield Strait, but if it is found further south it can flow down the slope and contribute to Weddell Sea Deep Water (WSDW). The influence of density on the spreading was also tested indicating that a denser plume reaches greater depths while lighter plumes do not interact with the WSDW

Short- and long-term vegetative propagation of two spartina species on a salt marsh in southern Brazil

Spartina alterniflora and Spartina densiflora are native salt marsh plants from the Atlantic coast; their habitats in Patos Lagoon estuary (southern Brazil) are characterized by a microtidal regime (<0.5 m) and, during El Niño events, high estuarine water levels and prolonged flooding due to elevated freshwater discharge from a 200,000-km2 watershed. During and between El Niño events, the vegetative propagation of these two Spartina species in the largest estuary of southern Brazil (Patos Lagoon) was evaluated by monitoring transplanted plants for 10 years (short-term study) and interpreting aerial photos of natural stands for 56 years (long-term study). During the short-term study, S. alterniflora quickly occupied mud flats (up to 208 cm year−1) by elongation of rhizomes, whereas S. densiflora showed a modest lateral spread (up to 13 cm year−1) and generated dense circular-shaped stands. However, moderate and strong El Niño events can promote excessive flooding and positive anomalies in the estuarine water level that reduce the lateral spread and competitive ability of S. densiflora. During the long-term study, natural stands of S. alterniflora and S. densiflora had steady lateral spread rates of 152 and 5.2 cm year−1, respectively, over mud flats. In the microtidal marshes of the southwest Atlantic, the continuous long-term lateral expansion of both Spartina species embodies periods of intense flooding stress (moderate and strong El Niños), when there is a decrease of vegetative propagation and less stressful low water periods of fast spread over mud flats (non-El Niño periods and weak intensity El Niños)

Sex-biased incidental mortality of albatrosses and petrels in longline fisheries: differential distributions at sea or differential access to baits mediated by sexual size dimorphism?

Skewed adult sex ratio (ASR) has been proposed as a common pattern in birds, frequently biased towards males and with larger biases in globally threatened species. In albatrosses and petrels, it has been suggested that differential mortality of one gender in fisheries is caused either by sexual size dimorphism giving males a competitive advantage, which allows more access of the larger sex (i.e. males) to discards and/or baits, or to at sea segregation of sexes. Here, we tested these hypotheses by determining ASRs in albatrosses and petrels trapped at sea when attending longline fishing vessels for discards in the southwestern Atlantic Ocean, and searched in the literature for patterns in ASR in albatrosses and petrels killed by fisheries in this area and elsewhere. We show that skewed ASR is common in albatrosses and petrels in the community attending vessels for discards, confirming results found for birds in general. There was no correlation between skewed ASR and conservation status, or between ASR and sexual size dimorphism. Our review of the sex of birds incidentally killed in fisheries found skewed ASR toward males, females or parity to be equally reported. Thus, sexual dimorphism in size does not explain skewed ASR in the community we sampled or in incidental captures in fisheries in the review. Differential at-sea distribution of sexes appears to be a better explanation of the patterns found in the community sampled at sea as well as skewed ASR in seabird fatalities, particularly distant from breeding areas