Holocene Climate and Catchment-Specific Responses to Climate Change, Recorded in a Transect of Icelandic Lakes
Monday, 14 December 2015: 10:20
2012 (Moscone West)
Holocene paleoclimate reconstructions from the northern North Atlantic landmasses exhibit greater responses to climate forcings than other Arctic regions presumably tied to changes in North Atlantic ocean-atmosphere circulation. Here we present an overview of high-resolution, precisely dated and PSV synchronized Holocene lake sediment records on Iceland, where we employ diverse proxies at sites spanning a broad modern climate gradient, from the presently glaciated highlands to the coastal lowlands. Despite substantial differences in catchment specific processes that influence each lake record, the multi-proxy reconstructions over the last 10 ka show remarkably consistent trends, especially throughout the mid to late Holocene cooling related to the slow decrease in summer insolation. Of particular note are highly non-linear abrupt departures of centennial scale summer cold periods such as at 5.5 ka, ~4.2 ka; ~3.0 ka, ~1.5 ka, 0.7 ka, and 0.2 ka. Some of the abrupt shifts may be related to Icelandic volcanism influencing catchment stability, but the lack of a full recovery to pre-existing values after the perturbation suggests increased periglacial activity, decreased vegetation cover, and glacier growth in Iceland. That these shifts reflect regional climate changes is also supported by contemporaneous shifts documented elsewhere in the northern North Atlantic region. Although timing and abruptness of these shifts is similar between our Icelandic lake records, their magnitude can differ substantially. Regional-scale factors such as volcanism likely modulate climatic responses to radiative forcing; and at the same time, local watershed characteristics like vegetation cover and soil properties produce site-specific environmental responses to climate change. Our Icelandic lake records provide opportunities to observe the precise timing of local climate shifts and corresponding environmental responses, and thus to disentangle these effects.