We present data from a laminated sediment core collected in the Edisto inlet (Ross Sea, Antarctica). The expanded record (14.6 m long) covers the last ca. 2800 years and it is dominated by dark- and light-brown diatom oozes. We used a suite of proxies which include diatom assemblages, bulk OC and TN, nitrogen and carbon stable isotopes, opal, grain size and biomarker analyses with focus on the new IPSO-25 proxy (di-unsaturated highly branched isoprenoid) of landfast sea ice. A sub-sample of well-defined dark and light laminae (n=33) exhibited a statistically different (t-test) composition in terms of stable carbon isotopes, IPSO-25, relative percentage of the diatom Corethron pennatum, as well as porosity. Dark laminae are likely indicative of spring blooms when the delta-13C signature and IPSO-25 concen- tration are high, whereas porosity is comparatively low. The heavy delta-13C signature and high IPSO-25 values are consistent with deposition of sea-ice diatoms growing in reduced availability of dissolved inorganic carbon typical of sea-ice matrix. By contrast, the IPSO-25 in light laminae decreases by up to three-orders of magnitude together with a marked decrease of delta-13C. We interpret these trends to reflect a protracted opening of the bay later in summer and a greater availability of carbon for photosynthesis. Under these conditions, the greater Corethron pennatum concentration in the light-brown laminae might indicate a different environment likely asso- ciated with open water conditions. In addition, the relatively higher abundance of Corethron pennatum resulted in a “sponge-like” matrix which explains the marked difference in porosity between light and dark laminae. The same suite of parameters were then analysed throughout the sediment core (n=300). Spectral analysis of the core data revealed a pervasive and persistent cyclicity at ∼90 years consistent with the Gleissberg solar cycle. Based on the information gained from the laminae analysis, we infer that through a top-down effect solar activity might influence regional wind patterns, which in turn exerts first-order control on the landfast sea ice dynamics and diatom ecology in the Edisto Inlet.
Late-Holocene record of environmental changes in the Ross Sea: from seasonal to centennial time scales.
Gariboldi K.;Morigi C.;Torricella F.;
2019-01-01
Abstract
We present data from a laminated sediment core collected in the Edisto inlet (Ross Sea, Antarctica). The expanded record (14.6 m long) covers the last ca. 2800 years and it is dominated by dark- and light-brown diatom oozes. We used a suite of proxies which include diatom assemblages, bulk OC and TN, nitrogen and carbon stable isotopes, opal, grain size and biomarker analyses with focus on the new IPSO-25 proxy (di-unsaturated highly branched isoprenoid) of landfast sea ice. A sub-sample of well-defined dark and light laminae (n=33) exhibited a statistically different (t-test) composition in terms of stable carbon isotopes, IPSO-25, relative percentage of the diatom Corethron pennatum, as well as porosity. Dark laminae are likely indicative of spring blooms when the delta-13C signature and IPSO-25 concen- tration are high, whereas porosity is comparatively low. The heavy delta-13C signature and high IPSO-25 values are consistent with deposition of sea-ice diatoms growing in reduced availability of dissolved inorganic carbon typical of sea-ice matrix. By contrast, the IPSO-25 in light laminae decreases by up to three-orders of magnitude together with a marked decrease of delta-13C. We interpret these trends to reflect a protracted opening of the bay later in summer and a greater availability of carbon for photosynthesis. Under these conditions, the greater Corethron pennatum concentration in the light-brown laminae might indicate a different environment likely asso- ciated with open water conditions. In addition, the relatively higher abundance of Corethron pennatum resulted in a “sponge-like” matrix which explains the marked difference in porosity between light and dark laminae. The same suite of parameters were then analysed throughout the sediment core (n=300). Spectral analysis of the core data revealed a pervasive and persistent cyclicity at ∼90 years consistent with the Gleissberg solar cycle. Based on the information gained from the laminae analysis, we infer that through a top-down effect solar activity might influence regional wind patterns, which in turn exerts first-order control on the landfast sea ice dynamics and diatom ecology in the Edisto Inlet.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
