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The Greenland Ice Sheet has been losing mass at an accelerating rate over the past 2 decades. Understanding ice mass and glacier changes during the preceding several hundred years prior to geodetic measurements is more difficult because evidence of past ice extent in many places was later overridden. Salt marshes provide the only continuous records of relative sea level (RSL) from close to the Greenland Ice Sheet that span the period of time during and since the Little Ice Age (LIA) and can be used to reconstruct ice mass gain and loss over recent centuries. Salt marsh sediments collected at the mouth of Dronning Marie Dal, close to the Greenland Ice Sheet margin in southeastern Greenland, record RSL changes over the past ca. 300 years through changing sediment and diatom stratigraphy. These RSL changes record a combination of processes that are dominated by local and regional changes in Greenland Ice Sheet mass balance during this critical period that spans the maximum of the LIA and 20th-century warming. In the early part of the record (1725–1762 CE) the rate of RSL rise is higher than reconstructed from the closest isolation basin at Timmiarmiut, but between 1762 and 1880 CE the RSL rate is within the error range of the rate of RSL change recorded in the isolation basin. RSL begins to slowly fall around 1880 CE, with a total amount of RSL fall of 0.09±0.1 m in the last 140 years. Modelled RSL, which takes into account contributions from post-LIA Greenland Ice Sheet glacio-isostatic adjustment (GIA), ongoing deglacial GIA, the global non-ice sheet glacial melt fingerprint, contributions from thermosteric effects, the Antarctic mass loss sea level fingerprint and terrestrial water storage, overpredicts the amount of RSL fall since the end of the LIA by at least 0.5 m. The GIA signal caused by post-LIA Greenland Ice Sheet mass loss is by far the largest contributor to this modelled RSL, and error in its calculation has a large impact on RSL predictions at Dronning Marie Dal. We cannot reconcile the modelled RSL and the salt marsh observations, even when moving the termination of the LIA to 1700 CE and reducing the post-LIA Greenland mass loss signal by 30 %, and a "budget residual" of +∼3 mm yr -1 since the end of the LIA remains unexplained. This new RSL record backs up other studies that suggest that there are significant regional differences in the timing and magnitude of the response of the Greenland Ice Sheet to the climate shift from the LIA into the 20th century. [ABSTRACT FROM AUTHOR]

The Greenland Ice Sheet has been losing mass at an accelerating rate over the past two decades. Understanding ice mass and glacier changes during the preceding several hundred years, prior to geodetic measurements, is more difficult because evidence of past ice extent in many places was later overridden. Saltmarshes provide the only continuous records of Relative Sea Level (RSL) from close to the Greenland Ice Sheet that span the period of time during and since the Little Ice Age (LIA) and can be used to reconstruct ice mass gain and loss over recent centuries. Saltmarsh sediments collected at the mouth of Dronning Marie Dal, close to the Greenland Ice Sheet margin in southeast Greenland, record RSL changes over the past c. 300 years through changing sediment and diatom stratigraphy. These RSL changes record a combination of processes that are dominated by local/regional changes in Greenland Ice Sheet mass balance during this critical period that spans the maximum of the LIA and 20th Century warming. In the early part of the record (1725-1762 CE) the rate of RSL rise is higher than reconstructed from the closest isolation basin at Timmiarmiut, but between 1762-1880 CE the RSL rate is within the error range of rate of RSL change recorded in the isolation basin. RSL begins to slowly fall around 1880 CE and then accelerates since the 1990s, with a total amount of RSL fall of 0.08 ±0.1 m in the last 140 years. Modelled RSL, which takes into account contributions from post-LIA Greenland Ice Sheet Glacio-isostatic Adjustment (GIA), ongoing deglacial GIA, the global non35 ice sheet glacial melt fingerprint, contributions from thermosteric effects, the Antarctic mass loss sea36 level fingerprint and terrestrial water storage, over-predicts the amount of RSL fall since the end of the LIA by at least 0.5 m. The GIA signal caused by post-LIA Greenland Ice Sheet mass loss is by far the largest contributor to this modelled RSL, and error in its calculation can have a large impact on RSL predictions at Dronning Marie Dal. We cannot reconcile the modelled RSL and the saltmarsh observations, even when moving the termination of the LIA to 1800 CE and reducing the post-LIA Greenland mass loss signal by 30 %, and a 'budget residual' of +~2.5 mm/yr since the end of the LIA remains unexplained. [ABSTRACT FROM AUTHOR]

The Greenland Ice Sheet has been losing mass at an accelerating rate over the past two decades. Understanding ice mass and glacier changes during the preceding several hundred years, prior to geodetic measurements, is more difficult because evidence of past ice extent in many places was later overridden. Saltmarshes provide the only continuous records of Relative Sea Level (RSL) from close to the Greenland Ice Sheet that span the period of time during and since the Little Ice Age (LIA) and can be used to reconstruct ice mass gain and loss over recent centuries. Saltmarsh sediments collected at the mouth of Dronning Marie Dal, close to the Greenland Ice Sheet margin in southeast Greenland, record RSL changes over the past c. 300 years through changing sediment and diatom stratigraphy. These RSL changes record a combination of processes that are dominated by local/regional changes in Greenland Ice Sheet mass balance during this critical period that spans the maximum of the LIA and 20th Century warming. In the early part of the record (1725–1762 CE) the rate of RSL rise is higher than reconstructed from the closest isolation basin at Timmiarmiut, but between 1762–1880 CE the RSL rate is within the error range of rate of RSL change recorded in the isolation basin. RSL begins to slowly fall around 1880 CE and then accelerates since the 1990s, with a total amount of RSL fall of 0.08 ±0.1 m in the last 140 years. Modelled RSL, which takes into account contributions from post-LIA Greenland Ice Sheet Glacio-isostatic Adjustment (GIA), ongoing deglacial GIA, the global non-ice sheet glacial melt fingerprint, contributions from thermosteric effects, the Antarctic mass loss sea-level fingerprint and terrestrial water storage, over-predicts the amount of RSL fall since the end of the LIA by at least 0.5 m. The GIA signal caused by post-LIA Greenland Ice Sheet mass loss is by far the largest contributor to this modelled RSL, and error in its calculation can have a large impact on RSL predictions at Dronning Marie Dal. We cannot reconcile the modelled RSL and the saltmarsh observations, even when moving the termination of the LIA to 1800 CE and reducing the post-LIA Greenland mass loss signal by 30 %, and a 'budget residual' of +~2.5 mm/yr since the end of the LIA remains unexplained. [ABSTRACT FROM AUTHOR]

Aim: While we understand broad climate drivers of insect distributions throughout the Arctic, less is known about the role of spatial processes in determining these relationships. As such, there is a need to understand how spatial controls may influence our interpretations of chironomid environment relationships. Here, we evaluated whether the distribution of chironomids followed spatial gradients, or were primarily controlled by environmental factors. Location: Eastern Canadian Arctic, Greenland, Iceland. Taxon: Non‐biting midges (Chironomidae). Methods: We examined chironomid assemblages from 239 lakes in the western North Atlantic Arctic region (specifically from the Arctic Archipelago of Canada, two parts of west Greenland (the southwest and central west) and northwest Iceland). We used a combination of unconstrained ordination (Self Organizing Maps); a simple method with only one data matrix (community data), and constrained ordination (Redundancy Analysis); a canonical ordination with two datasets where we extracted structure of community related to environmental data. These methods allowed us to model chironomid assemblages across a large bioregional dimension and identify specific differences between regions that were defined by common taxa represented across all regions in high frequencies, as well as rare taxa distinctive to each region found in low frequencies. We then evaluated the relative importance of spatial processes versus local environmental factors. Results: We find that environmental controls explained the largest amount of variation in chironomid assemblages within each region, and that spatial controls are only significant when crossing between regions. Broad‐scale biogeographic effects on chironomid distributions are reflected by the distinct differences among chironomid assemblages of Iceland, central‐west Greenland, and eastern Canada, defined by the presence of certain common and low‐frequency, rare taxa for each region. Environmental gradients, especially temperature, defined species distributions within each region, whereas spatial processes combine with environmental gradients in determining what mix of species characterizes each broad and geographically distinct island region in our study. Main conclusions: While biogeographic context is important for defining interpretations of environmental controls on species distributions, the primary control on distributions within regions is environmental. These influences are fundamentally important for reconstructing past environmental change and better understanding historical distributions of these insect indicators. [ABSTRACT FROM AUTHOR]