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Cape, MR, Vernet M, Skvarca P, Marinsek S, Scambos T, Domack E.  2015.  Foehn winds link climate-driven warming to ice shelf evolution in Antarctica. Journal of Geophysical Research-Atmospheres. 120(21):11037-11057.   10.1002/2015JD023465   Abstract

Rapid warming of the Antarctic Peninsula over the past several decades has led to extensive surface melting on its eastern side, and the disintegration of the Prince Gustav, Larsen A, and Larsen B ice shelves. The warming trend has been attributed to strengthening of circumpolar westerlies resulting from a positive trend in the Southern Annular Mode (SAM), which is thought to promote more frequent warm, dry, downsloping foehn winds along the lee, or eastern side, of the peninsula. We examined variability in foehn frequency and its relationship to temperature and patterns of synoptic-scale circulation using a multidecadal meteorological record from the Argentine station Matienzo, located between the Larsen A and B embayments. This record was further augmented with a network of six weather stations installed under the U.S. NSF LARsen Ice Shelf System, Antarctica, project. Significant warming was observed in all seasons at Matienzo, with the largest seasonal increase occurring in austral winter (+3.71 degrees C between 1962-1972 and 1999-2010). Frequency and duration of foehn events were found to strongly influence regional temperature variability over hourly to seasonal time scales. Surface temperature and foehn winds were also sensitive to climate variability, with both variables exhibiting strong, positive correlations with the SAM index. Concomitant positive trends in foehn frequency, temperature, and SAM are present during austral summer, with sustained foehn events consistently associated with surface melting across the ice sheet and ice shelves. These observations support the notion that increased foehn frequency played a critical role in precipitating the collapse of the Larsen B ice shelf.

Olli, K, Halvorsen E, Vernet M, Lavrentyev PJ, Franze G, Sanz-Martin M, Paulsen ML, Reigstad M.  2019.  Food web functions and interactions during spring and summer in the Arctic Water inflow region: Investigated through inverse modeling. Frontiers in Marine Science. 6   10.3389/fmars.2019.00244   AbstractWebsite

We used inverse modeling to reconstruct major planktonic food web carbon flows in the Atlantic Water inflow, east and north of Svalbard during spring (18-25 May) and summer (9-13 August), 2014. The model was based on three intensively sampled stations during both periods, corresponding to early, peak, and decline phases of a Phaeocystis and diatom dominated bloom (May), and flagellates dominated post bloom stages (August). The food web carbon flows were driven by primary production (290-2,850 mg C m(-2) d(-1)), which was channeled through a network of planktonic compartments, and ultimately respired (180-1200 mg C m(2) d(-1)), settled out of the euphotic zone as organic particles (145-530 mg C m(-2) d(-1)), or accumulated in the water column in various organic pools. The accumulation of dissolved organic carbon was intense (1070 mg C m(-2) d(-1)) during the early bloom stage, slowed down during the bloom peak (400 mg C m(-2) d(-1)), and remained low during the rest of the season. The heterotrophic bacteria responded swiftly to the massive release of new DOC by high but decreasing carbon assimilation rates (from 534 to 330 mg C m(-2) d(-1)) in May. The net bacterial production was low during the early and peak bloom (26-31 mg C m(-2) d(-1)) but increased in the late and post bloom phases (>50 mg C m(-2) d(-1)). The heterotrophic nanoflagellates did not respond predictably to the different bloom phases, with relatively modest carbon uptake, 30-170 mg C m(2) d(-1). In contrast, microzooplankton increased food intake from 160 to 380 mg C m(2) d(-1) during the buildup and decline phases, and highly variable carbon intake 46-624 mg C m(2) d(-1), during post bloom phases. Mesozooplankton had an initially high but decreasing carbon uptake in May (220-48 mg C m(-2) d(-1)), followed by highly variable carbon consumption during the post bloom stages (40-190 mg C m(-2) d(-1)). Both, micro- and mesozooplankton shifted from almost pure herbivory (92-97% of total food intake) during the early bloom phase to an herbivorous, detritovorous and carnivorous mixed diet as the season progressed. Our results indicate a temporal decoupling between the microbial and zooplankton dominated heterotrophic carbon flows during the course of the bloom in a highly productive Atlantic gateway to the Arctic Ocean.

Smith, KL, Robison BH, Helly JJ, Kaufmann RS, Ruhl HA, Shaw TJ, Twining BS, Vernet M.  2007.  Free-drifting icebergs: Hot spots of chemical and biological enrichment in the Weddell Sea. Science. 317:478-482.   10.1126/science.1142834   AbstractWebsite

The proliferation of icebergs from Antarctica over the past decade has raised questions about their potential impact on the surrounding pelagic ecosystem. Two free-drifting icebergs, 0.1 and 30.8 square kilometers in aerial surface area, and the surrounding waters were sampled in the northwest Weddell Sea during austral spring 2005. There was substantial enrichment of terrigenous material, and there were high concentrations of chlorophyll, krill, and seabirds surrounding each iceberg, extending out to a radial distance of similar to 3.7 kilometers. Extrapolating these results to all icebergs in the same size range, with the use of iceberg population estimates from satellite surveys, indicates that they similarly affect 39% of the surface ocean in this region. These results suggest that free-drifting icebergs can substantially affect the pelagic ecosystem of the Southern Ocean and can serve as areas of enhanced production and sequestration of organic carbon to the deep sea.