Abstract. Multiple year-round (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015) records of the bulk and size-segregated composition of aerosol were obtained at the inland site of Concordia located in East Antarctica. The well-marked maximum of non-seasalt sulfate (nssSO 4 ) in January (100 ± 28 ng m −3 versus 4.4 ± 2.3 ng m −3 in July) is consistent with observations made at the coast (280 ± 78 ng m −3 in January versus 16 ± 9 ng m −3 in July at Dumont d'Urville, for instance). In contrast, the well-marked maximum of MSA at the coast in January (60 ± 23 ng m −3 at Dumont d'Urville) is not observed at Concordia (5.2 ± 2.0 ng m −3 in January). Instead, the MSA level at Concordia peaks in October (5.6 ± 1.9 ng m −3 ) and March (14.9 ± 5.7 ng m −3 ). As a result, a surprisingly low MSA-to-nssSO 4 ratio (R MSA ) is observed at Concordia in mid-summer (0.05 ± 0.02 in January versus 0.25 ± 0.09 in March). We find that the low value of R MSA in mid-summer at Concordia is mainly driven by a drop of MSA levels that takes place in submicron aerosol (0.3 µm diameter). The drop of MSA coincides with periods of high photochemical activity as indicated by high ozone levels, strongly suggesting the occurrence of an efficient chemical destruction of MSA over the Antarctic plateau in mid-summer. The relationship between MSA and nssSO 4 levels is examined separately for each season and indicates that concentration of non-biogenic sulfate over the Antarctic plateau does not exceed 1 ng m −3 in fall and winter and remains close to 5 ng m −3 in spring. This weak non-biogenic sulfate level is discussed in the light of radionuclides ( 210 Pb, 10 Be, and 7 Be) also measured on bulk aerosol samples collected at Concordia. The findings highlight the complexity in using MSA in deep ice cores extracted from inland Antarctica as a proxy of past dimethyl sulfide emissions from the Southern Ocean.

The aerosol climatology at the coastal Antarctic Neumayer Station (NM) was investigated based on continuous, 25‐yr long observations of biogenic sulphur components (methanesulfonate and non–sea salt sulphate), sea salt and nitrate. Although significant long‐term trends could only be detected for nitrate (−3.6 ± 2.5% per year between 1983 and 1993 and +4.0 ± 3.2% per year from 1993–2007), non‐harmonic periodicities between 2 and 5 yr were typical for all species. Dedicated time series analyses revealed that relations to sea ice extent and various circulation indices are weak at best or not significant. In particular, no consistent link between sea ice extent and sea salt loadings was evident suggesting only a rather local relevance of the NM sea salt record. Nevertheless, a higher Southern Annular Mode index tended to entail a lower biogenic sulphur signal. In examining the spatial uniformity of the NM findings we contrasted them to respective 17 yr records from the coastal Dumont d’Urville Station. We found similar long‐term trends for nitrate, indicating an Antarctic‐wide but not identifiable atmospheric signal, although any significant impact of solar activity or pollution could be ruled out. No inter‐site variability on the multiannual scale was evident for the other ionic compounds.

We investigated the variability of 210 Pb, 7 Be and 10 Be in coastal Antarctic aerosol samples based on continuous, monthly and annually resolved time series obtained from Neumayer Station over the period 1983 to 2008. Clear seasonal cycles peaking in the local summer half year stand out as a common feature of all three radionuclide records. Time series analyses suggest that significant multiannual changes are confined to a 4-6 yr periodicity resembling that of the Southern Annual Mode index in case of 210 Pb and to the expected decadal solar cycle in case of the cosmogenic Be-isotopes. Both, changes in the meridional transport and surface inversion strength appear to drive the seasonal 210 Pb cycle, which generally peaks in November. In contrast, stratospheric air mass intrusions are proved to be the main reason for the Be-isotopes seasonality. This finding is revealed by enhanced 10 Be/ 7 Be ratios occurring during late summer / early autumn broadly concurrently with the individual Be-isotopes and the 7 Be/ 210 Pb ratio. The 10 Be and 7 Be records clearly reflect the decadal, solar-modulated production signal but, for unknown reasons, they substantially differ in their detailed pattern. It is ruled out, that an excess 7 Be production by solar energetic particles was responsible for this mismatch.

The aerosol climatology at the coastal Antarctic Neumayer Station (NM) was investigated based on continuous, 25 years long observations of biogenic sulfur components (methanesulfonate and non sea salt sulfate), sea salt and nitrate. Whilst significant long-term trends could only be detected for nitrate (-3.6±2.5% per year between 1983 and 1993 and +4.0±3.2% per year from 1993-2007), non-harmonic periodicities between 2 and 5 years were typical for all species. Dedicated time series analyses revealed that relations to sea ice extent and various circulation indices are weak at best or not significant. In particular, no consistent link between sea ice extent and sea salt loadings was evident suggesting only a rather local relevance of the NM sea salt record. Nevertheless, a higher Southern Annular Mode index tended to entail a lower biogenic sulfur signal. In examining the spatial uniformity of the NM findings we contrasted them to respective 17 years records from the coastal Dumont d'Urville Station (DDU). We found similar long term trends for nitrate, indicating an Antarctic-wide but not identifiable atmospheric signal, though any significant impact of solar activity or pollution could be ruled out. No inter-site variability on the multi annual scale was evident for the other ionic compounds.

A reconstruction of historical discharges of 236U into the Northeast Atlantic Ocean by nuclear installations is presented. The nuclear reprocessing facilities Sellafield (SF), Great Britain (GB) and La Hague (LH), France and potentially also the nuclear fuel processing installation Springfields (SP), GB represent the main contributors of 236U in the Northeast Atlantic Ocean. Because data on 236U releases is lacking, 236U discharges from SP and SF are estimated based on the U‐isotopic systematics found in the discharges from LH. The resulting reconstruction of 236U releases indicates that, until 2013, a total of (95 ± 32) kg of 236U was discharged from SF, SP, and LH. In a second step, the reconstructed 236U releases are combined with 129I data from literature and oceanic and atmospheric box models are used to derive the 129I/236U and 236U/238U input functions that, for example, can be used to calculate tracer ages of Atlantic Waters in the Arctic Ocean. Our conceptual results show that the combination of 129I/236U and 236U/238U generally allows the estimation of tracer ages over the past approximately 25 years if contributions of 236U from global fallout are considered. Finally, as a proof of concept, the new method is applied to calculate tracer ages of Arctic Ocean surface samples (collected in 2011/2012) and the results are in good agreement with literature data. We conclude that the combination of 129I/236U with 236U/238U in a dual tracer approach provides a sensitive tool for the calculation of tracer ages and ventilation rates in the North Atlantic region.