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In the 1980s, a series of articles explored the potential importance of transient rheology in the glacial isostatic adjustment (GIA) process (e.g., Peltier et al., Geophys. Res. Lett., 1980; Sabadini et al., Geophys. Res. Lett., 1985; Yuen et al., J. Geophys. Res., 1986). However, in the absence of observational evidence for a time dependent viscous response, this level of additional modeling complexity fell out of favor in the GIA community. Recently, a comparison of viscosity models inferred from Holocene relative sea level data and modern crustal uplift rates in Greenland – the latter suggestive of a significantly lower Maxwell viscosity than the former – has renewed interest in the intriguing possibility of transient mantle creep (Adhikari et al., Earth Planet. Sci. Lett., 2021). However, an unambiguous argument that transient rheology is necessary must rule out the possibility that a class of (Maxwell) viscosity models with general depth and lateral variability may reconcile both data sets. We present numerically derived 1-D sensitivity kernels for the relative sea level and uplift rate observations that demonstrate that these two data sets have independent sensitivities to variations in depth-dependent mantle viscosity. Moreover, we explore – within a broad class of such 1-D models – the level of fit that can be achieved to these data using a multi-layer Maxwell viscosity profile. Future work on this important, outstanding issue should extend this analysis of uniqueness using 3-D sensitivity kernels derived via adjoint methods (Crawford et al., Geophys. J. Int., 2018)., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

In this paper we evaluate new data and those from previous studies in northwest Scotland and perform a modelling study to test the hypothesis that the Storegga tsunami (submarine slope failure off the continental shelf of Central Norway dated to 8120–8175 bp) impacted this region. The model used is a 2D non-linear, non-conservative, Shallow Water Equation solver incorporating inundation and realistic glacial isostatic adjustment-corrected palaeobathymetry, with horizontal resolution down to 30 m at sites of interest. The 15 coastal study sites analysed range from south of the Isle of Skye to Assynt. We predict run-up between 2.7 and 9.4 m above contemporaneous mean tide level across the region, with the highest on the west coast of the Outer Hebrides, the east coast of Skye and at the head of long sea lochs east of Skye. We re-evaluate evidence from previously studied open coastal marshes, isolation basins and barrier locations for the tsunami and suggest that in many locations the Storegga tsunami is the most likely cause of erosion, deposition and changes in microfossil assemblages in the early Holocene. The predictions of wave height and inundation produced by the tsunami modelling fit well with the range of available field evidence in the region. We predict significant wave heights at least as far south as Mull on the west coast.

Supplemental material, sj-docx-1-hol-10.1177_09596836221080756 for Reliability of mangrove radiocarbon chronologies: A case study from Mah��, Seychelles by Juliet Sefton, Sarah Woodroffe, Philippa Ascough and Nicole Khan in The Holocene

MWP-1A sources inversion results from Lin et al., 'A reconciled solution of Meltwater Pulse 1A sources using sea-level fingerprinting'. This spreadsheet contains four sheets: Database descriptions, Empirical, Uniform and Final. The first sheet provides an overview of this dataset and the last three sheets contain the output from this study.

In the Northern Hemisphere, an insolation driven Early to Middle Holocene Thermal Maximum was followed by a Neoglacial cooling that culminated during the Little Ice Age (LIA). Here, we review the glacier response to this Neoglacial cooling in Greenland. Changes in the ice margins of outlet glaciers from the Greenland Ice Sheet as well as local glaciers and ice caps are synthesized Greenland-wide. In addition, we compare temperature reconstructions from ice cores, elevation changes of the ice sheet across Greenland and oceanographic reconstructions from marine sediment cores over the past 5,000 years. The data are derived from a comprehensive review of the literature supplemented with unpublished reports. Our review provides a synthesis of the sensitivity of the Greenland ice margins and their variability, which is critical to understanding how Neoglacial glacier activity was interrupted by the current anthropogenic warming. We have reconstructed three distinct periods of glacier expansion from our compilation: two older Neoglacial advances at 2,500 – 1,700 yrs. BP (Before Present = 1950 CE, Common Era) and 1,250 – 950 yrs. BP; followed by a general advance during the younger Neoglacial between 700-50 yrs. BP, which represents the LIA. There is still insufficient data to outline the detailed spatio-temporal relationships between these periods of glacier expansion. Many glaciers advanced early in the Neoglacial and persisted in close proximity to their present-day position until the end of the LIA. Thus, the LIA response to Northern Hemisphere cooling must be seen within the wider context of the entire Neoglacial period of the past 5,000 years. Ice expansion appears to be closely linked to changes in ice sheet elevation, accumulation, and temperature as well as surface-water cooling in the surrounding oceans. At least for the two youngest Neoglacial advances, volcanic forcing triggering a sea-ice /ocean feedback, could explain their initiation. There are probably several LIA glacier fluctuations since the first culmination close to 1250 CE (Common Era) and available data suggests ice culminations in the 1400s, early to mid-1700s and early to mid-1800s CE. The last LIA maxima lasted until the present deglaciation commenced around 50 yrs. BP (1900 CE). The constraints provided here on the timing and magnitude of LIA glacier fluctuations delivers a more realistic background validation for modelling future ice sheet stability.

Due to their large mass, ice sheets induce significant stresses in the Earth’s crust. Stress release during deglaciation can trigger large-magnitude earthquakes, as indicated by surface faults in northern Europe. Although glacially-induced stresses have been analyzed in northern Europe, they have not yet been analyzed for Greenland. We know that the Greenland Ice Sheet experienced a large melting period in the early Holocene, and so here, we analyze glacially-induced stresses during deglaciation for Greenland for the first time. Instability occurs in southern Greenland, where we use a combined analysis of past sea level indicators and a model of glacially-triggered fault reactivation to show that deglaciation of the Greenland Ice Sheet may have caused a large magnitude earthquake around 10,600 years ago offshore south-western Greenland. The earthquake may have shifted relative sea level observations by several meters. If the earthquake-induced stress release was created during a single event, it could have produced a tsunami in the North Atlantic Ocean with runup heights of up to 5 m in the British Isles and up to 7.5 m along Canadian coasts.

Northern hemisphere temperatures reached their Holocene minimum and most glaciers reached their maximum during The Little Ice Age (LIA), but the timing of specific cold intervals is site-specific. In southern Greenland, we have compiled data from organic matter incorporated in LIA sediments, used as a signal for ice-free terrain being overridden by LIA glacier advances, and data from threshold lakes showing the onset of glacier-fed lakes, thus revealing the advance-maximum phase initiating the LIA. Finally, we have compiled lichenometry results indicating the onset of bedrock vegetation succeeding ice retreat. Our results show that the advance of glaciersduring the LIA occurs early after the Medieval Warm Period terminating soon after 1200 AD and culminates c. 1500-1600 AD. Historical maps also show that many glaciers on the western coast occupy a still-stand near the LIA maximum until 1900 AD before retreat commence.Thus in southern Greenland, we define LIA as the period between the first signs of Late Holocene glacier readvance and the latest onset of retreat – i.e. from ca. 1200 to c. 1900. During this period northern hemisphere annual mean temperatures, although fluctuating, were generally below the 1961-1990 average, with the coldest interval between c. 1600 and 1800. Even though winter temperatures may have dominated the cooling, also the summer temperatures which are most closely correlated with glacier mass balances, dropped, to c. 0.6 below the average in the northern hemisphere including the Arctic. Furthermore, the glacier response seems to be mirroredby a oceanic cooling between 500-1000 AD, followed by onset of the LIA at 1150-1250 AD as seen in the relative strength of warm subsurface water and the influence of the East Greenland Current.

Northern hemisphere temperatures reached their Holocene minimum and most glaciers reached their maximum during The Little Ice Age (LIA), but the timing of specific cold intervals is site-specific. In southern Greenland, we have compiled data from organic matter incorporated in LIA sediments, used as a signal for ice-free terrain being overridden by LIA glacier advances, and data from threshold lakes showing the onset of glacier-fed lakes, thus revealing the advance-maximum phase initiating the LIA. Finally, we have compiled lichenometry results indicating the onset of bedrock vegetation succeeding ice retreat. Our results show that the advance of glaciersduring the LIA occurs early after the Medieval Warm Period terminating soon after 1200 AD and culminates c. 1500-1600 AD. Historical maps also show that many glaciers on the western coast occupy a still-stand near the LIA maximum until 1900 AD before retreat commence.Thus in southern Greenland, we define LIA as the period between the first signs of Late Holocene glacier readvance and the latest onset of retreat – i.e. from ca. 1200 to c. 1900. During this period northern hemisphere annual mean temperatures, although fluctuating, were generally below the 1961-1990 average, with the coldest interval between c. 1600 and 1800. Even though winter temperatures may have dominated the cooling, also the summer temperatures which are most closely correlated with glacier mass balances, dropped, to c. 0.6 below the average in the northern hemisphere including the Arctic. Furthermore, the glacier response seems to be mirroredby a oceanic cooling between 500-1000 AD, followed by onset of the LIA at 1150-1250 AD as seen in the relative strength of warm subsurface water and the influence of the East Greenland Current.