Fjord systems and archives: a review

<p>Fjords are glacially over-deepened semi-enclosed marine basins, typically with entrance sills separating their deep waters from the adjacent coastal waters which restrict water circulation and thus oxygen renewal. The location of fjords is principally controlled by the occurrence of ice sheets, either modern or ancestral. Fjords are therefore geomorphological features that represent the transition from the terrestrial to the marine environment and, as such, have the potential to preserve evidence of environmental change. Typically, most fjords have been glaciated a number of times and some high-latitude fjords still possess a resident glacier. In most cases, glacial erosion through successive glacial/interglacial cycles has ensured the removal of sediment sequences within the fjord. Hence the stratigraphic record in fjords largely preserves a glacial-deglacial cycle of deposition over the last 18 ka or so. Sheltered water and high sedimentation rates have the potential to make fjords ideal depositional environments for preserving continuous records of climate and environmental change with high temporal resolution. In addition to acting as high-resolution environmental archives, fjords can also be thought of as mini-ocean sedimentary basin laboratories. Fjords remain an understudied and often neglected sedimentary realm. With predictions of warming climates, changing ocean circulation and rising sea levels, this volume is a timely look at these environmentally sensitive coastlines. </p

Fjord systems and archives: a review

<p>Fjords are glacially over-deepened semi-enclosed marine basins, typically with entrance sills separating their deep waters from the adjacent coastal waters which restrict water circulation and thus oxygen renewal. The location of fjords is principally controlled by the occurrence of ice sheets, either modern or ancestral. Fjords are therefore geomorphological features that represent the transition from the terrestrial to the marine environment and, as such, have the potential to preserve evidence of environmental change. Typically, most fjords have been glaciated a number of times and some high-latitude fjords still possess a resident glacier. In most cases, glacial erosion through successive glacial/interglacial cycles has ensured the removal of sediment sequences within the fjord. Hence the stratigraphic record in fjords largely preserves a glacial-deglacial cycle of deposition over the last 18 ka or so. Sheltered water and high sedimentation rates have the potential to make fjords ideal depositional environments for preserving continuous records of climate and environmental change with high temporal resolution. In addition to acting as high-resolution environmental archives, fjords can also be thought of as mini-ocean sedimentary basin laboratories. Fjords remain an understudied and often neglected sedimentary realm. With predictions of warming climates, changing ocean circulation and rising sea levels, this volume is a timely look at these environmentally sensitive coastlines. </p

DataSheet1_Glacial history and depositional environments in little Storfjorden and Hambergbukta of Arctic Svalbard since the younger dryas.docx

Geophysical and lithological data provide crucial information for the understanding of glacial history in Arctic Svalbard. In this study, we reconstructed the glacier-induced depositional environments of Little Storfjorden and its tributary, Hambergbukta, over the last 13 ka to better understand the glacial history of southeastern Svalbard. The combined uses of swath-bathymetry, high-resolution seismic stratigraphy, and multiple-proxy measurements of sediment cores allowed us to define five steps of glacier-induced depositional environments: 1) deposition of massive, semi-consolidated gravelly sandy mud (Facies 1) during re-advance or still-stand of the marine-based glaciers/ice streams in Little Storfjorden during Younger Dryas (13–12 ka); 2) deposition of massive mud to gravelly sandy mud (Facies 2A and B) during glacial retreat until the earliest Holocene (12–10.1 ka); 3) sediment winnowing by enhanced bottom currents during the early to middle Holocene (10.1–3.7 ka); 4) deposition of bioturbated sandy mud (Facies 3) with high productivity under seasonal sea ice conditions during the late Holocene (3.7–0.7 ka); and 5) deposition of (slightly) bioturbated sandy to gravelly mud (Facies 4) affected by glacier surges since Little Ice Age (LIA) (Facies 4). In addition to seismic stratigraphy, depositional patterns of IRD in Little Storfjorden indicate that the glacier surges in Hambergbukta occurred only after ∼0.7 ka. This suggests that the terminal moraine complex (TMC) represents the maximum extent of the LIA surges, which argues against the recent inference for the TMC formation during pre-LIA. This study shows the importance of multiple parameters to better understand the current behavior of tidewater glaciers in the Svalbard fjords in response to rapid climate change.</p

Table1_Glacial history and depositional environments in little Storfjorden and Hambergbukta of Arctic Svalbard since the younger dryas.XLSX

Geophysical and lithological data provide crucial information for the understanding of glacial history in Arctic Svalbard. In this study, we reconstructed the glacier-induced depositional environments of Little Storfjorden and its tributary, Hambergbukta, over the last 13 ka to better understand the glacial history of southeastern Svalbard. The combined uses of swath-bathymetry, high-resolution seismic stratigraphy, and multiple-proxy measurements of sediment cores allowed us to define five steps of glacier-induced depositional environments: 1) deposition of massive, semi-consolidated gravelly sandy mud (Facies 1) during re-advance or still-stand of the marine-based glaciers/ice streams in Little Storfjorden during Younger Dryas (13–12 ka); 2) deposition of massive mud to gravelly sandy mud (Facies 2A and B) during glacial retreat until the earliest Holocene (12–10.1 ka); 3) sediment winnowing by enhanced bottom currents during the early to middle Holocene (10.1–3.7 ka); 4) deposition of bioturbated sandy mud (Facies 3) with high productivity under seasonal sea ice conditions during the late Holocene (3.7–0.7 ka); and 5) deposition of (slightly) bioturbated sandy to gravelly mud (Facies 4) affected by glacier surges since Little Ice Age (LIA) (Facies 4). In addition to seismic stratigraphy, depositional patterns of IRD in Little Storfjorden indicate that the glacier surges in Hambergbukta occurred only after ∼0.7 ka. This suggests that the terminal moraine complex (TMC) represents the maximum extent of the LIA surges, which argues against the recent inference for the TMC formation during pre-LIA. This study shows the importance of multiple parameters to better understand the current behavior of tidewater glaciers in the Svalbard fjords in response to rapid climate change.</p