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Sediment core ER11-16 from Køge Bugt in Southeast Greenland is used to assess early Holocene palaeoceanographic changes and sediment rafting from icebergs calved from the large outlet glaciers in the area. Diatom analysis reconstructs variability in surface water temperature, salinity and sea-ice concentrations, and benthic foraminiferal assemblages is used to reconstruct subsurface ocean conditions. We report Holocene Thermal Maximum in Southeast Greenland during the early Holocene (at least since onset of the record 9100 cal yr BP) until around 4500 cal yr BP, which contrasts with a delay until the mid-Holocene of the Holocene Thermal Maximum in South and Southwest Greenland. The early Holocene warming in Southeast Greenland was caused by a combination of high solar insolation and a weakened subpolar gyre, both of which served to warm the Irminger Current waters subducting onto the shelf. At the same time, the surface temperature was relatively high and sea-ice cover in the polar surface waters of the East Greenland Current was relatively low. High levels of iceberg rafting occurred in Køge Bugt during the early Holocene, synchronously with these warm oceanic temperatures. This is attributed to an increase in iceberg production from the extensive, but retreating, Greenland Ice Sheet. The warm surface conditions were interrupted by a marked and short-lived increase in sea ice around 8200 years ago, providing the first evidence of this global cold episode in Southeast Greenland. After 4500 cal. yr BP, sea-ice cover increased with an expansion of the East Greenland Current, suppressing the inflow of warmer subsurface Irminger Current water to the Southeast Greenland shelf. We relate this oceanic shift to the decreased Northern Hemisphere summer solar insolation. Multi-centennial variability is observed in the grain size spectrum of iceberg rafted debris; a finding we interpret in the context of palaeoceanographic changes.

Abstract 2918 Background: Monosomal karyotype (MK) is defined as the presence of two or more distinct autosomal chromosome monosomies or a single autosomal monosomy associated with at least one structural abnormality (Breems DA et al. J Clin Oncol 2008; 26: 4791). In acute myeloid leukemia (AML), MK has been associated with a worse prognosis than otherwise complex karyotype, regardless of the specific type of autosomal chromosome involved (Breems DA et al. J Clin Oncol 2008; 26: 4791). Whether or not these observations also hold true for myelodysplastic syndromes (MDS) is currently unknown. Objective: To determine if MDS with complex karyotype can be prognostically sub-stratified further based on the presence or absence of MK and if prognosis in MDS with MK is in addition affected by the presence or absence of monosomy 7 or monosomy 5. Methods: The Mayo Clinic database for MDS was used to identify consecutive patients with complex karyotype, defined as the presence of three or more numerical or structural cytogenetic abnormalities. World Health Organization (WHO) criteria were used for MDS diagnosis and leukemic transformation (Vardiman JW et al. Blood 2009; 114: 937). Overall and leukemia-free survivals were calculated from the time of initial cytogenetic studies documenting complex karyotype. Results: A total of 127 MDS patients (median age 70 years; 79 males) with complex karyotype were identified. Amongst them, 106 (83%) met the above-stipulated criteria for MK and 21 (17%) had complex karyotype without monosomies. The MK in the 106 patients included monosomy 7 and/or monosomy 5 in 73 cases. The three complex karyotype subsets (i.e. complex without monosomies vs. MK that included monosomy 7 and/or 5 vs. MK excluding monosomy 7 or 5) were not significantly different in terms of age and sex distribution, hemoglobin level, leukocyte or platelet count, bone marrow blast percentage or International Prognostic Scoring System (IPSS) risk score. However, survival was significantly inferior in patients with MK compared to those with complex karyotype without monosomies (p=0.01; HR 1.9, 95% CI 1.1–3.3). Multivariable analysis identified MK (p=0.002), advanced age (p=0.0004), increased bone marrow blast percentage (0.04), but not IPSS risk category (p=0.34), as independent risk factors for survival. Interestingly, there was no difference in survival among MK patients further sub-stratified by the presence or absence of monosomy 7 and/or monosomy 5 (Figure 1). Although not statistically significant, leukemia-free survival was also worse in patients with MK compared to those with complex karyotype (p=0.11; HR 2.7, 95% CI 0.8–9.0); none of the aforementioned variables significantly affected leukemia-free survival. Conclusions: Monosomal karyotype in MDS identifies a prognostically worse subgroup of patients with complex karyotype. Furthermore, in the context of MK, autosomal monosomies other than monosomy 7 or monosomy 5 are prognostically as detrimental. Disclosures: No relevant conflicts of interest to declare.