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This study investigates the postglacial sea-level history of eastern Cumberland Peninsula, a region of Baffin Island, Nunavut, where submerged terraces were documented in the 1970s. The elevation gradient of emerged postglacial marine-limit deltas and fiord-head moraines led Arthur Dyke to propose a conceptual model for continuous postglacial submergence of the eastern peninsula. Multibeam mapping over the past decade has revealed eight unequivocal submerged deltas at 19-45 m below present sea level (b.s.l.) and other relict shore-zone landforms (boulder barricade, spits, and sill platform) at 16-51 m b.s.l. Over a distance of 115 km from Qikiqtarjuaq to Cape Dyer, the submerged coastal features increase in depth toward the east, with a slope (0.36 m/km) less than that of the marine-limit shoreline previously documented (0.58-0.62 m/km). The submerged ice-proximal deltas, deglacial ice limits, and radiocarbon ages constrain the postglacial lowstand between 9.9 and 1.4 ka cal BP. The glacial-isostatic model ICE-7G_NA (VM7) computes a lowstand relative sea level at 8.0 ka, the depth of which increases eastward at 0.28 m/km. The difference between observed and model-derived lowstand depths ranges from 1 m in the west to 10 m in the east and the predicted tilt is significantly less than observed (p - 0.0008). The model results, emerging data on Holocene glacial readvances on eastern Baffin Island, and evidence for proglacial delta formation point to a Cockburn (9.5-8.2 ka) age for the lowstand, most likely later in this range. This study confirms the 1970s conceptual model of postglacial submergence in outer Cumberland Peninsula and provides field evidence for further refinement of glacial-isostatic adjustment models. Key words: submerged deltas, Cockburn Substage, Holocene lowstand, glacial-isostatic adjustment model, multibeam bathymetry, Arctic. L'étude se penche sur l'histoire postglaciaire du niveau de la mer de l'est de la péninsule de Cumberland, une région de l'île de Baffin (Nunavut), où des terrasses immergées ont été documentées dans les années 1970. Le gradient d'élévation de deltas postglaciaires émergés à la limite marine et de moraines d'amont de fjord ont mené Arthur Dyke à proposer un modèle conceptuel pour l'immersion postglaciaire continue de la partie est de la péninsule. La cartographie bathymétrique multifaisceaux réalisée au cours de la dernière décennie a révélé huit deltas immergés non équivoques à 19^15 m sous le niveau de la mer (snm) actuel et d'autres reliques de formes de relief littorales (barricade de bloc, flèches et plateforme de seuil) à 16-51 m snm. Sur une distance de 115 km de Qikiqtarjuaq à Cape Dyer, la profondeur des éléments littoraux immergés augmente vers l'est, suivant une pente (0,36 m/km) inférieure à celle du littoral de la limite marine documentée précédemment (0,58-0,62 m/km). Les deltas juxtaglaciaires immergés, les limites de déglaciation et des âges au carbone radioactif situent le bas niveau postglaciaire entre 9,9 ka cal BP et 1,4 ka cal BP. Le modèle glacio-isostatique ICE-7G_NA (VM7) donne un bas niveau par rapport au niveau de la mer à 8,0 ka, dont la profondeur augmente vers l'est à raison de 0,28 m/km. L'écart entre les profondeurs du bas niveau observée et modélisée va de 1 m à l'ouest à 10 m à l'est et l'inclinaison prédite est significativement moindre que l'inclinaison observée (p = 0,0008). Les résultats de modélisation, de nouvelles données sur des réavancées glaciaires dans l'est de l'île de Baffin à l'Holocène et des preuves de la formation de deltas proglaciaires indiqueraient que le bas niveau s'est produit à la phase Cockburn (9,5-8,2 ka), vraisemblablement vers la fin de cette fourchette. L'étude confirme le modèle conceptuel des années 1970 d'immersion postglaciaire de la partie externe de la péninsule de Cumberland et fournit des observations de terrain permettant de peaufiner les modèles d'ajustement glacio-isostatiques. [Traduit par la Rédaction] Mots-clés : deltas immergés, sous-phase Cockburn, bas niveau Holocène, modèle d'ajustement glacio-isostatique, bathymétrie multifaisceaux, Arctique., Introduction Submerged postglacial coastal landforms are predicted by glacialisostatic adjustment (GIA) models (Quinlan and Beaumont 1981; Tarasov and Peltier 2004) and documented around the margins of late Quaternary ice sheets [...]

A synthesis of new and existing data allows Heinrich Stadial 11 (HS11), a prominent Northern Hemisphere cold event, to be linked to the timing of peak sea-level rise during glacial termination T-II, whereas rapid sea-level rise in T-I is shown to clearly post-date Heinrich Stadial 1, so fundamentally different mechanisms seem to be at work during glacial terminations. Anatomy of a glacial termination A central goal of palaeoclimate research is that of deciphering the mechanisms responsible for major state shifts in the Earth system, such as between glacial and interglacial conditions. This has proven difficult enough even for the last glacial termination (T-I), much less termination II (T-II), which ended glacial conditions about 130,000 years ago. Gianluca Marino et al. use new and existing data to demonstrate a link, within uncertainties, between Heinrich Stadial 11 (HS11) -- a prominent Northern Hemisphere cold event -- and the timing of peak sea level rise during T-II. A strong Southern Hemisphere warming also occurred during HS11, consistent with the idea of a bipolar seesaw that would probably have promoted Antarctic ice sheet melting. In contrast, rapid sea level rise in T-1 clearly postdated Heinrich Stadial 1. Possibly in response to differing CO.sub.2 and insolation conditions during T-I and T-II, fundamentally different mechanisms seem to be at work in triggering glacial terminations. Our current understanding of ocean-atmosphere-cryosphere interactions at ice-age terminations relies largely on assessments of the most recent (last) glacial-interglacial transition.sup.1,2,3, Termination I (T-I). But the extent to which T-I is representative of previous terminations remains unclear. Testing the consistency of termination processes requires comparison of time series of critical climate parameters with detailed absolute and relative age control. However, such age control has been lacking for even the penultimate glacial termination (T-II), which culminated in a sea-level highstand during the last interglacial period that was several metres above present.sup.4. Here we show that Heinrich Stadial 11 (HS11), a prominent North Atlantic cold episode.sup.5,6, occurred between 135 [plus or minus] 1 and 130 [plus or minus] 2 thousand years ago and was linked with rapid sea-level rise during T-II. Our conclusions are based on new and existing.sup.6,7,8,9 data for T-II and the last interglacial that we collate onto a single, radiometrically constrained chronology. The HS11 cold episode.sup.5,6 punctuated T-II and coincided directly with a major deglacial meltwater pulse, which predominantly entered the North Atlantic Ocean and accounted for about 70 per cent of the glacial-interglacial sea-level rise.sup.8,9. We conclude that, possibly in response to stronger insolation and CO.sub.2 forcing earlier in T-II, the relationship between climate and ice-volume changes differed fundamentally from that of T-I. In T-I, the major sea-level rise clearly post-dates.sup.3,10,11 Heinrich Stadial 1. We also find that HS11 coincided with sustained Antarctic warming, probably through a bipolar seesaw temperature response.sup.12, and propose that this heat gain at high southern latitudes promoted Antarctic ice-sheet melting that fuelled the last interglacial sea-level peak., Author(s): G. Marino [sup.1] , E. J. Rohling [sup.1] [sup.2] , L. Rodríguez-Sanz [sup.1] , K. M. Grant [sup.1] , D. Heslop [sup.1] , A. P. Roberts [sup.1] , J. [...]

Ice volume (and hence sea level) and deep-sea temperature are key measures of global climate change. Sea level has been documented using several independent methods over the past 0.5 million years (Myr). Older periods, however, lack such independent validation; all existing records are related to deep-sea oxygen isotope ([δ.sup.18]O) data that are influenced by processes unrelated to sea level. For deep-sea temperature, only one continuous high-resolution (Mg/Ca-based) record exists, with related sea-level estimates, spanning the past 1.5 Myr. Here we present a novel sea-level reconstruction, with associated estimates of deep-sea temperature, which independently validates the previous 0-1.5 Myr reconstruction and extends it back to 5.3 Myr ago. We find that deep-sea temperature and sea level generally decreased through time, but distinctly out of synchrony, which is remarkable given the importance of ice-albedo feedbacks on the radiative forcing of climate. In particular, we observe a large temporal offset during the onset of Plio-Pleistocene ice ages, between a marked cooling step at 2.73 Myr ago and the first major glaciation at 2.15 Myr ago. Last, we tentatively infer that ice sheets may have grown largest during glacials with more modest reductions in deep-sea temperature., To understand better the potential response of ice volume (sea level) to global warming, there is a need for continuous, highly resolved and well-quantified records of sea-level variations associated with [...]

The timing of sea-level change provides important constraints on the mechanisms driving Earth's climate between glacial and interglacial states. Fossil corals constrain the timing of past sea level by their suitability for dating and their growth position dose to sea level The coral-derived age for the last deglaciation is consistent with climate change forced by Northern Hemisphere summer insolation (NHI), but the timing of the penultimate deglaciation is more controversial We found, by means of uranium/thorium dating of fossil corals, that sea level during the penultimate deglaciation had risen to ~85 meters below the present sea level by 137,000 years ago, and that it fluctuated on a millennial time scale during deglaciation. This indicates that the penultimate deglaciation occurred earlier with respect to NHI than the last deglacial, beginning when NHI was at a minimum.

Global warming and the predicted adverse environmental implications in coastal areas have prompted the use of a quantitative pedological approach to model the history of relative sea-level rise and the subsequent lateral migration of marshes (deforestation) during the pedogenic transformation of Ultisols (forest soils) to Histosols (marsh soils). The modeling was based on the transgressing soil-landscape concept and data collected from sampling units along two marsh transects in Dorchester County, Maryland. In low-relief submerging environments, coastal marshes accrete vertically and migrate laterally over adjacent Ultisols to keep pace with sea-level rise. The marsh substrate is organic in nature overlying what once were upland forest soils. The history of relative sea-level rise was a two-step linear function illustrating acceleration in the last two centuries. During the last l50 yr, the [sup.210]pb-based rate of relative sea-level rise averaged 2.4 [+ or -] 0.7 mm [yr.sup.-1]. Before the last few hundred years, the long-term [sup.14]C-based rate of relative sea-level rise was 0.82 [+ or -] 0.15 mm [yr.sup.-1]. The rate of lateral migration of coastal marshes (deforestation) showed similar acceleration following the history of relative sea-level rise. During the last 150 yr, the average rate of lateral migration of marshes (deforestation) ranged from 3.51 [+ or -] 2.0 to 6.78 [+ or -] 7.4 m [yr.sup.-1]. Before the last l50 yr, the average long-term rate of lateral migration of marshes (deforestation) ranged between 0.18 [+ or -] 0.07 and 1.27 [+ or -] 1.2 m [yr.sup.-1]. Within a given region where sea-level rise and tidal range remain constant, the rate of lateral migration of marshes is a function of site characteristics and the slope of the adjacent uplands. The predicted rate of lateral migration of marshes in the next century ranges from 3.2 to 33 m [yr.sup.-1], averaging 14 [+ or -] 11 m [yr.sup.-1]. Assuming that the present rate of relative sea-level rise remains constant, the time needed to complete the pedogenic transformation of Ultisols to Histosols is 180 [+ or -] 35 yr. The most conservative future scenario of sea-level rise has reduced this time by 63%. The projected sequestration of C, total N, and pyrite in the newly formed coastal marshes during the next 100 yr average 231 [+ or -] 124, 11.7 [+ or -] 6.30, and 6.63 [+ or -] 3.57 Mg [ha.sup.-1], respectively. These projections are half the nutrient sequestration potential of existing coastal marshes.

The isotopic composition of oxygen in sea water correlates with changes in global mean sea level. Microfossils carrying oxygen-isotope signals have been used to extend sea-level records as far back [...]